theories on the origin of life essay 300 words

7 theories on the origin of life

The answer to the origin of life remains unknown, but here are scientists best bets

The origin of life might be discovered by looking into our DNA

An electric spark

Molecules of life met on clay

Deep-sea vents
Born from ice
Understanding DNA
Simple beginnings
Life came from space

Additional resources

Bibliography.

The origin of life on Earth began more than 3 billion years ago, evolving from the most basic of microbes into a dazzling array of complexity over time. But how did the first organisms on the only known home to life in the universe develop from the primordial soup?

Science remains undecided and conflicted as to the exact origin of life, also known as abiogenesis. Even the very definition of life is contested and rewritten, with one study published in the J ournal of Biomolecular Structure and Dynamics , suggesting uncovering 123 different published definitions.

Although science still seems unsure, here are some of the many different scientific theories on the origin of life on Earth.

It started with an electric spark

Lightning may have provided the spark needed for life to begin.Electric sparks can generate amino acids and sugars from an atmosphere loaded with water, methane, ammonia and hydrogen , as was shown in the famous Miller-Urey experiment in 1952, according to Scientific American . The experiment's findings suggested that lightning might have helped create the key building blocks of life on Earth in its early days. Over millions of years, larger and more complex molecules could form.

Although research since then has revealed the early atmosphere of Earth was actually hydrogen-poor, scientists have suggested that volcanic clouds in the early atmosphere might have held methane, ammonia and hydrogen and been filled with lightning as well, according to the University of California

The first molecules of life might have met on clay, according to an idea elaborated by organic chemist Alexander Graham Cairns-Smith at the University of Glasgow in Scotland. Cairns-Smith proposed in his 1985 controversial book “ Seven Clues to the Origin of Life'' , that clay crystals preserve their structure as they grow and stick together to form areas exposed to different environments and trap other molecules along the way and organise them into patterns much like our genes do now.

– What is the difference between prokaryotic and eukaryotic cells?

– What is biology?

– What are bacteria?

– What is an amoeba?

– Is there water on Mars?

The main role of DNA is to store information on how other molecules should be arranged. Genetic sequences in DNA are essentially instructions on how amino acids should be arranged in proteins. Cairns-Smith suggests that mineral crystals in clay could have arranged organic molecules into organized patterns. After a while, organic molecules took over this job and organized themselves.

Although Cairns-Smith's theory certainly gave scientists food for thought in the 1980s, it has still not been widely accepted by the scientific community.

Life began at deep-sea vents

A deep-sea vent releasing fluid into the water

The deep-sea vent theory suggests that life may have begun at submarine hydrothermal vents spewing elements key to life, such as carbon and hydrogen-, according to the journal Nature Reviews Microbiology .

Hydrothermal vents can be found in the darkest depths of the ocean floors, typically on diverging continental plates, according to the Natural History Museum . These vents erupt fluid which is superheated by the Earth’s core as it passes up through the crust, before being ejected at the vets. During its journey through the crust it collects dissolved gases and minerals, such as carbon and hydrogen.

Their rocky nooks could then have concentrated these molecules together and provided mineral catalysts for critical reactions. Even now, these vents, rich in chemical and thermal energy, sustain vibrant ecosystems.

Abiogenesis by way of hydrothermal vents continues to be investigated as a plausible cause of life on Earth. In 2019, scientists at University College London , successfully created protocells (non-living structures that help scientists understand the origins of life) under similar hot, alkaline environmental conditions to hydrothermal vents.

Life had a chilly start

Ice might have covered the oceans 3 billion years ago and facilitated the birth of life. "Key organic compounds thought to be important in the origin of life are more stable at lower temperatures,” Jeffrey Bada at the University of California, told New Scientist . At normal temperatures these compounds, such as simple sets of amino acids, are sparsely populated in water, but when frozen become concentrated and facilitate the emergence of life, according to Bada’s work published in the journal I carus .

Ice also might have protected fragile organic compounds in the water below from ultraviolet light and destruction from cosmic impacts. The cold might have also helped these molecules to survive longer, enabling key reactions to happen.

The answer lies in understanding DNA formation

Nowadays DNA needs proteins in order to form, and proteins require DNA to form, so how could these have formed without each other? The answer may be RNA , which can store information like DNA, serve as an enzyme like proteins, and help create both DNA and proteins, according to the journal Molecular Biology of the Cell . Later DNA and proteins succeeded this "RNA world," because they are more efficient.

RNA still exists and performs several functions in organisms, including acting as an on-off switch for some genes. The question still remains how RNA got here in the first place. Some scientists think the molecule could have spontaneously arisen on Earth, while others say that was very unlikely to have happened.

Life had simple beginnings

Instead of developing from complex molecules such as RNA, life might have begun with smaller molecules interacting with each other in cycles of reactions. These might have been contained in simple capsules akin to cell membranes, and over time more complex molecules that performed these reactions better than the smaller ones could have evolved, scenarios dubbed "metabolism-first" models, as opposed to the "gene-first" model of the "RNA world" hypothesis.

Life was brought here from elsewhere in space

An illustration of an asteroid heading for Earth

Perhaps life did not begin on Earth at all, but was brought here from elsewhere in space, a notion known as panspermia, according to NASA . For instance, rocks regularly get blasted off Mars by cosmic impacts, and a number of Martian meteorites have been found on Earth that some researchers have controversially suggested brought microbes over here, potentially making us all Martians originally. Other scientists have even suggested that life might have hitchhiked on comets from other star systems. However, even if this concept were true, the question of how life began on Earth would then only change to how life began elsewhere in space.

For more information into the theories of life’s origins check out “ The Stairway To Life: An Origin-Of-Life Reality Check ” by Change Laura Tan and “ The Mystery of Life's Origin ” by Charles B. Thaxton, et al.

Matthew Levy et al, “Prebiotic Synthesis of Adenine and Amino Acids Under Europa-like Conditions”, Icarus, Volume 145, June 2000, https://doi.org/10.1006/icar.2000.6365

William Martin, “Hydrothermal vents and the origin of life”, Nature Reviews Microbiology, Volume 6, September 2008, https://doi.org/10.1038/nrmicro1991

K. A. Dill and L. Agozzino, “Driving forces in the origins of life”, Open biology, Volume 11, February 2021, ttps://doi.org/10.1098/rsob.200324

Ben K. D. Pearce et al, “Origin of the RNA world: The fate of nucleobases in warm little ponds”, PNAS, Volume 114, October 2017, https://doi.org/10.1073/pnas.1710339114

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The origin of life on earth, explained.

The origin of life on Earth stands as one of the great mysteries of science. Various answers have been proposed, all of which remain unverified. To find out if we are alone in the galaxy, we will need to better understand what geochemical conditions nurtured the first life forms. What water, chemistry and temperature cycles fostered the chemical reactions that allowed life to emerge on our planet? Because life arose in the largely unknown surface conditions of Earth’s early history, answering these and other questions remains a challenge.

Several seminal experiments in this topic have been conducted at the University of Chicago, including the Miller-Urey experiment that suggested how the building blocks of life could form in a primordial soup.

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When did life on Earth begin?

Where did life on Earth begin?

What are the ingredients of life on earth, what are the major scientific theories for how life emerged, what is chirality and why is it biologically important, what research are uchicago scientists currently conducting on the origins of life, when did life on earth begin .

Earth is about 4.5 billion years old. Scientists think that by 4.3 billion years ago, Earth may have developed conditions suitable to support life. The oldest known fossils, however, are only 3.7 billion years old. During that 600 million-year window, life may have emerged repeatedly, only to be snuffed out by catastrophic collisions with asteroids and comets.

The details of those early events are not well preserved in Earth’s oldest rocks. Some hints come from the oldest zircons, highly durable minerals that formed in magma. Scientists have found traces of a form of carbon—an important element in living organisms— in one such 4.1 billion-year-old zircon . However, it does not provide enough evidence to prove life’s existence at that early date.

Two possibilities are in volcanically active hydrothermal environments on land and at sea.

Some microorganisms thrive in the scalding, highly acidic hot springs environments like those found today in Iceland, Norway and Yellowstone National Park. The same goes for deep-sea hydrothermal vents. These chimney-like vents form where seawater comes into contact with magma on the ocean floor, resulting in streams of superheated plumes. The microorganisms that live near such plumes have led some scientists to suggest them as the birthplaces of Earth’s first life forms.

Organic molecules may also have formed in certain types of clay minerals that could have offered favorable conditions for protection and preservation. This could have happened on Earth during its early history, or on comets and asteroids that later brought them to Earth in collisions. This would suggest that the same process could have seeded life on planets elsewhere in the universe.

The recipe consists of a steady energy source, organic compounds and water.

Sunlight provides the energy source at the surface, which drives photosynthesis. On the ocean floor, geothermal energy supplies the chemical nutrients that organisms need to live.

Also crucial are the elements important to life . For us, these are carbon, hydrogen, oxygen, nitrogen, and phosphorus. But there are several scientific mysteries about how these elements wound up together on Earth. For example, scientists would not expect a planet that formed so close to the sun to naturally incorporate carbon and nitrogen. These elements become solid only under very cold temperatures, such as exist in the outer solar system, not nearer to the sun where Earth is. Also, carbon, like gold, is rare at the Earth’s surface. That’s because carbon chemically bonds more often with iron than rock. Gold also bonds more often with metal, so most of it ends up in the Earth’s core. So, how did the small amounts found at the surface get there? Could a similar process also have unfolded on other planets?

The last ingredient is water. Water now covers about 70% of Earth’s surface, but how much sat on the surface 4 billion years ago? Like carbon and nitrogen, water is much more likely to become a part of solid objects that formed at a greater distance from the sun. To explain its presence on Earth, one theory proposes that a class of meteorites called carbonaceous chondrites formed far enough from the sun to have served as a water-delivery system.

There are several theories for how life came to be on Earth. These include:

Life emerged from a primordial soup

As a University of Chicago graduate student in 1952, Stanley Miller performed a famous experiment with Harold Urey, a Nobel laureate in chemistry. Their results explored the idea that life formed in a primordial soup.

Miller and Urey injected ammonia, methane and water vapor into an enclosed glass container to simulate what were then believed to be the conditions of Earth’s early atmosphere. Then they passed electrical sparks through the container to simulate lightning. Amino acids, the building blocks of proteins, soon formed. Miller and Urey realized that this process could have paved the way for the molecules needed to produce life.

Scientists now believe that Earth’s early atmosphere had a different chemical makeup from Miller and Urey’s recipe. Even so, the experiment gave rise to a new scientific field called prebiotic or abiotic chemistry, the chemistry that preceded the origin of life. This is the opposite of biogenesis, the idea that only a living organism can beget another living organism.

Seeded by comets or meteors

Some scientists think that some of the molecules important to life may be produced outside the Earth. Instead, they suggest that these ingredients came from meteorites or comets.

“A colleague once told me, ‘It’s a lot easier to build a house out of Legos when they’re falling from the sky,’” said Fred Ciesla, a geophysical sciences professor at UChicago. Ciesla and that colleague, Scott Sandford of the NASA Ames Research Center, published research showing that complex organic compounds were readily produced under conditions that likely prevailed in the early solar system when many meteorites formed.

Meteorites then might have served as the cosmic Mayflowers that transported molecular seeds to Earth. In 1969, the Murchison meteorite that fell in Australia contained dozens of different amino acids—the building blocks of life.

Comets may also have offered a ride to Earth-bound hitchhiking molecules, according to experimental results published in 2001 by a team of researchers from Argonne National Laboratory, the University of California Berkeley, and Lawrence Berkeley National Laboratory. By showing that amino acids could survive a fiery comet collision with Earth, the team bolstered the idea that life’s raw materials came from space.

In 2019, a team of researchers in France and Italy reported finding extraterrestrial organic material preserved in the 3.3 billion-year-old sediments of Barberton, South Africa. The team suggested micrometeorites as the material’s likely source. Further such evidence came in 2022 from samples of asteroid Ryugu returned to Earth by Japan’s Hayabusa2 mission. The count of amino acids found in the Ryugu samples now exceeds 20 different types .

In 1953, UChicago researchers published a landmark paper in the Journal of Biological Chemistry that marked the discovery of the pro-chirality concept , which pervades modern chemistry and biology. The paper described an experiment showing that the chirality of molecules—or “handedness,” much the way the right and left hands differ from one another—drives all life processes. Without chirality, large biological molecules such as proteins would be unable to form structures that could be reproduced.

Today, research on the origin of life at UChicago is expanding. As scientists have been able to find more and more exoplanets—that is, planets around stars elsewhere in the galaxy—the question of what the essential ingredients for life are and how to look for signs of them has heated up.

Nobel laureate Jack Szostak joined the UChicago faculty as University Professor in Chemistry in 2022 and will lead the University’s new interdisciplinary Origins of Life Initiative to coordinate research efforts into the origin of life on Earth. Scientists from several departments of the Physical Sciences Division are joining the initiative, including specialists in chemistry, astronomy, geology and geophysics.

“Right now we are getting truly unprecedented amounts of data coming in: Missions like Hayabusa and OSIRIS-REx are bringing us pieces of asteroids, which helps us understand the conditions that form planets, and NASA’s new JWST telescope is taking astounding data on the solar system and the planets around us ,” said Prof. Ciesla. “I think we’re going to make huge progress on this question.”

Last updated Sept. 19, 2022.

Faculty Experts

Clara Blättler

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Origin of Life Theories

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While religions have relied on creation stories to explain how life on Earth began, scientists have tried to hypothesize possible ways that inorganic molecules (the building blocks of life) joined together to form living cells . There are several hypotheses about how life started on Earth that are still being studied today. So far, there is no definitive proof for any of the theories. However, there is strong evidence for several scenarios.

Hydrothermal Vents

The early atmosphere of the Earth was what we would now consider a quite hostile environment. With little to no oxygen, there was not a protective ozone layer around the Earth like we have now. This means the scorching ultraviolet rays from the Sun could easily reach the surface of the Earth. Most ultraviolet light is now blocked by our ozone layer, which makes it possible for life to inhabit the land. Without the ozone layer, life on land was not possible.

This leads many scientists to conclude that life must have begun in the oceans. Considering most of the Earth is covered in water, this assumption makes sense. It also is not a leap to realize ultraviolet rays can penetrate the shallowest areas of water, so life may have begun somewhere deep in the ocean depths where it would have been protected from that ultraviolet light.

On the ocean floor, there are areas known as hydrothermal vents . These incredibly hot underwater areas are teeming with very primitive life to this day. Scientists who believe in the hydrothermal vent theory argue that these very simple organisms could have been the first forms of life on Earth.

Panspermia Theory

Adastra / Getty Images

Another consequence of having little to no atmosphere around the Earth is that meteors often entered the Earth's gravitational pull and crashed into the planet. This still happens in modern times, but our very thick atmosphere and ozone layer help burn the meteors up before they reach the ground and cause damage. However, since those layers of protection did not exist when life was first forming, the meteors that struck the Earth were extremely large and caused great damage.

Because of these large meteor strikes, scientists have hypothesized that some of the meteors that struck the Earth may have carried very primitive cells, or at least the building blocks of life. Panspermia theory does not try to explain how life began in outer space; that is beyond the scope of the hypothesis. With the frequency of meteor strikes all over the planet, not only could this hypothesis explain where life came from, but it could also explain how life spread out over various geographic areas.

Primordial Soup

Carny / Wikimedia Commons / CC BY 2.5

In 1953, the Miller-Urey experiment was all the buzz. Commonly referred to as the " primordial soup " concept, scientists showed how the building blocks of life, such as amino acids, could be created with only a few inorganic "ingredients" in a lab setting that was set up to mimic the conditions of early Earth. Previous scientists, such as Oparin and Haldane, had hypothesized that organic molecules could be created from inorganic molecules that could be found in the atmosphere of the young Earth. However, they were never able to duplicate the conditions themselves.

Later, as Miller and Urey took on the challenge, they were able to show in a lab setting that using just a few ancient ingredients such as water, methane, ammonia, and electricity to simulate lightning strikes—a combination of materials they called the "primordial soup"—they could generate several of the building blocks that make up life. While, at the time, this was a huge discovery and lauded as the answer to how life began on Earth, it was later determined that some of the "ingredients" in the "primordial soup" were in fact not present in the atmosphere of early Earth. However, it was still important to note that organic molecules were made relatively easily out of inorganic pieces, and this process may have played a role in the development of life on Earth.

Understanding Chemical Evolution
Early Life Theories: Primordial Soup
Early Life Theories - Panspermia Theory
The Oxygen Revolution
Early Life Theories - Hydrothermal Vents
Learn About the Different Types of Cells: Prokaryotic and Eukaryotic
Chemosynthesis Definition and Examples
Life on Earth During the Precambrian Time Span
The Four Eras of the Geologic Time Scale
Questions to Ask Your Biology Teacher About Evolution
Glossary of Terms Regarding Evolution
Does Life Exist Elsewhere in the Cosmos?
7 Extinction Level Events That Could End Life as We Know It
Ozone Layer Depletion
Flashes in the Sky: The Origins of Meteors
How Meteors Form and What They Are

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18.9: The Origin of Life

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John W. Kimball
Tufts University & Harvard

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To account for the origin of life on our earth requires solving several problems:

How the organic molecules that define life, e.g. amino acids, nucleotides, were created.
How these were assembled into macromolecules, e.g. proteins and nucleic acids, - a process requiring catalysts.
How these were able to reproduce themselves.
How these were assembled into a system delimited from its surroundings (i.e., a cell).

A number of theories address each of these problems. As for the first problem, four scenarios have been proposed. Organic molecules:

were synthesized from inorganic compounds in the atmosphere,
rained down on earth from outer space,
were synthesized at hydrothermal vents on the ocean floor,
were synthesized when comets or asteroids struck the early earth.

Scenario 1: Miller's Experiment

Stanley Miller, a graduate student in biochemistry, built the apparatus shown in Figure \(\PageIndex{1}\). He filled it with water (H 2 O), methane (CH 4 ), ammonia (NH 3 ) and hydrogen (H 2 ), but no oxygen. He hypothesized that this mixture resembled the atmosphere of the early earth. The mixture was kept circulating by continuously boiling and then condensing the water. The gases passed through a chamber containing two electrodes with a spark passing between them.

At the end of a week, Miller used paper chromatography to show that the flask now contained several amino acids as well as some other organic molecules. However, it is now thought that the atmosphere of the early earth was not rich in methane and ammonia - essential ingredients in Miller's experiments. In the years since Miller's work, many variants of his procedure have been tried. Virtually all the small molecules that are associated with life have been formed:

17 of the 20 amino acids used in protein synthesis, and all the purines and pyrimidines used in nucleic acid synthesis.
But abiotic synthesis of ribose - and thus of nucleotides - has been much more difficult. However, success in synthesizing pyrimidine ribonucleotides under conditions that might have existed in the early earth was reported in the 14 May 2009 issue of Nature .
And in 2015, chemists in Cambridge England led by John Sutherland reported that they had been able to synthesize precursors of 12 of the 20 amino acids and two (of the four) ribonucleotides used by life as well as glycerol-1-phosphate, a precursor of lipids. They created all of these molecules using only hydrogen cyanide (HCN) and hydrogen sulfide (H 2 S) irradiated with ultraviolet light in the presence of mineral catalysts.

Scenario 2: Molecules from Outer Space

Astronomers, using infrared spectroscopy, have identified a variety of organic molecules in interstellar space, including methane (CH 4 ), methanol (CH 3 OH), formaldehyde (HCHO), cyanoacetylene (HC 3 N) (which in spark-discharge experiments is a precursor to the pyrimidine cytosine ), polycyclic aromatic hydrocarbonsas well as such inorganic building blocks as carbon dioxide (CO 2 ), carbon monoxide (CO), ammonia (NH 3 ), hydrogen sulfide (H 2 S), and hydrogen cyanide (HCN).

There have been several reports of producing amino acids and other organic molecules in laboratories by taking a mixture of molecules known to be present in interstellar space such as ammonia (NH 3 ), carbon monoxide (CO), methanol (CH 3 OH) and water (H 2 O), hydrogen cyanide (HCN) and exposing it to a temperature close to that of space (near absolute zero) and intense ultraviolet (UV) radiation. Whether or not the molecules that formed terrestrial life arrived here from space, there is little doubt that organic matter continuously rains down on the earth (estimated at 30 tons per day).

Alternatively, organic molecules can be transport to Earth via meteorites as demonstrated with the Murchison Meteorite that that fell near Murchison, Australia on 28 September 1969. This meteorite turned out to contain a variety of organic molecules including: purines and pyrimidines, polyols - compounds with hydroxyl groups on a backbone of 3 to 6 carbons such as glycerol and glyceric acid (sugars are polyols) and the amino acids listed in Table \(\PageIndex{1}\). The amino acids and their relative proportions were quite similar to the products formed in Miller's experiments.

Murchison meteorite at the The National Museum of Natural History (Washington). (CC SA-BY 3.0; :Basilicofresco ).

Contamination?

The question is if these molecules identified in the Murchison meteorite were simply terrestrial contaminants that got into the meteorite after it fell to earth? Probably not:

Some of the samples were collected on the same day it fell and subsequently handled with great care to avoid contamination.
The polyols contained the isotopes carbon-13 and hydrogen-2 (deuterium) in greater amounts than found here on earth.
The samples lacked certain amino acids that are found in all earthly proteins.
Only L amino acids occur in earthly proteins, but the amino acids in the meteorite contain both D and L forms (although L forms were slightly more prevalent).

Scenario 3: Deep-Sea Hydrothermal Vents

Some deep-sea hydrothermal vents discharge copious amounts of hydrogen, hydrogen sulfide, and carbon dioxide at temperatures around 100°C. (These are not "black smokers".) These gases bubble up through chambers rich in iron sulfides (FeS, FeS 2 ). These can catalyze the formation of simple organic molecules like acetate. (And life today depends on enzymes that have Fe and S atoms in their active sites.)

Scenario 4: Laboratory Synthesis of Nucleobases Under Conditions Mimicking the Impact of Asteroids or Comets on the Early Earth

Researchers in the Czech Republic reported in 2014 that they had succeeded in the abiotic synthesis of adenine (A), guanine (G), cytosine (C), and uracil (U) — the four bases found in RNA (an RNA beginning?) and three of the four found in DNA. They achieved this by bombarding a mixture of formamide and clay with powerful laser pulses that mimicked the temperature and pressure expected when a large meteorite strikes the earth. Formamide is a simple substance, CH 3 NO, thought to have been abundant on the early earth and containing the four elements fundamental to all life.

Assembling Polymers

Another problem is how polymers - the basis of life itself - could be assembled.

In solution, hydrolysis of a growing polymer would soon limit the size it could reach.
Abiotic synthesis produces a mixture of L and D enantiomers. Each inhibits the polymerization of the other. (So, for example, the presence of D amino acids inhibits the polymerization of L amino acids (the ones that make up proteins here on earth).

This has led to a theory that early polymers were assembled on solid, mineral surfaces that protected them from degradation, and in the laboratory polypeptides and polynucleotides (RNA molecules) containing about ~50 units have been synthesized on mineral (e.g., clay) surfaces.

An RNA Beginning?

All metabolism depends on enzymes and, until recently, every enzyme has turned out to be a protein. But proteins are synthesized from information encoded in DNA and translated into mRNA. So here is a chicken-and-egg dilemma. The synthesis of DNA and RNA requires proteins. So proteins cannot be made without nucleic acids and nucleic acids cannot be made without proteins. The discovery that certain RNA molecules have enzymatic activity provides a possible solution. These RNA molecules — called ribozymes — incorporate both the features required of life: storage of information and the ability to act as catalysts.

While no ribozyme in nature has yet been found that can replicate itself, ribozymes have been synthesized in the laboratory that can catalyze the assembly of short oligonucleotides into exact complements of themselves. The ribozyme serves as both the template on which short lengths of RNA ("oligonucleotides" are assembled following the rules of base pairing and the catalyst for covalently linking these oligonucleotides.

In principal, the minimal functions of life might have begun with RNA and only later did proteins take over the catalytic machinery of metabolism and DNA take over as the repository of the genetic code. Several other bits of evidence support this notion of an original "RNA world":

In the cell, all deoxyribonucleotides are synthesized from ribonucleotide precursors.
Many bacteria control the transcription and/or translation of certain genes with RNA molecules, not protein molecules.

Reproduction?

Perhaps the earliest form of reproduction was a simple fission of the growing aggregate into two parts - each with identical metabolic and genetic systems intact.

The First Cell?

To function, the machinery of life must be separated from its surroundings - some form of extracellular fluid (ECF). This function is provided by the plasma membrane. Today's plasma membranes are made of a double layer of phospholipids. They are only permeable to small, uncharged molecules like H 2 O, CO 2 , and O 2 . Specialized transmembrane transporters are needed for ions, hydrophilic, and charged organic molecules (e.g., amino acids and nucleotides) to pass into and out of the cell.

However, the same Szostak lab that produced the finding described above reported in the 3 July 2008 issue of Nature that fatty acids, fatty alcohols, and monoglycerides - all molecules that can be synthesized under prebiotic conditions - can also form lipid bilayers and these can spontaneously assemble into enclosed vesicles.

Unlike phospholipid vesicles, these

admit from the external medium charged molecules like nucleotides
admit from the external medium hydrophilic molecules like ribose
grow by self-assembly
are impermeable to, and thus retain, polymers like oligonucleotides.

These workers loaded their synthetic vesicles with a short single strand of deoxycytidine (dC) structured to provide a template for its replication. When the vesicles were placed in a medium containing (chemically modified) dG, these nucleotides entered the vesicles and assembled into a strand of Gs complementary to the template strand of Cs. Here, then, is a simple system that is a plausible model for the creation of the first cells from the primeval "soup" of organic molecules.

From Unicellular to Multicellular Organisms

This transition is probably the easiest to understand.

Several colonial flagellated green algae provide a clue. These species are called colonial because they are made up simply of clusters of independent cells. If a single cell of Gonium , Pandorina , or Eudorina is isolated from the rest of the colony, it will swim away looking quite like a Chlamydomonas cell. Then, as it undergoes mitosis, it will form a new colony with the characteristic number of cells in that colony.

(The figures are not drawn to scale. Their sizes range from Chlamydomonas which is about 10 µm in diameter - little larger than a human red blood cell - to Volvox whose sphere is some 350 µm in diameter - visible to the naked eye.)

The situation in Pleodorina and Volvox is different. In these organisms, some of the cells of the colony (most in Volvox) are not able to live independently. If a nonreproductive cell is isolated from a Volvox colony, it will fail to reproduce itself by mitosis and eventually will die. What has happened? In some way, as yet unclear, Volvox has crossed the line separating simple colonial organisms from truly multicellular ones. Unlike Gonium, Volvox cannot be considered simply a colony of individual cells. It is a single organism whose cells have lost their ability to live independently. If a sufficient number of them become damaged, the entire sphere of cells will die.

What has Volvox gained? In giving up their independence, the cells of Volvox have become specialists. No longer does every cell carry out all of life's functions (as in colonial forms); instead certain cells specialize to carry out certain functions while leaving other functions to other specialists. In Volvox this process goes no further than having certain cells specialize for reproduction while others, unable to reproduce themselves, fulfill the needs for photosynthesis and locomotion.

In more complex multicellular organisms, the degree of specialization is carried much further. Each cell has one or two precise functions to carry out. It depends on other cells to carry out all the other functions needed to maintain the life of the organism and thus its own.

The specialization and division of labor among cells is the outcome of their history of differentiation. One of the great problems in biology is how differentiation arises among cells, all of which having arisen by mitosis, share the same genes.

The genomes of both Chlamydomonas and Volvox have been sequenced. Although one is unicellular, the other multicellular, they have not only about the same number of protein-encoding genes (14,516 in Chlamydomonas, 14,520 in Volvox) but most of these are homologous. Volvox has only 58 genes that have no relatives in Chlamydomonas and even fewer unique mRNAs.

At one time, many of us would have expected that a multicellular organism like Volvox with its differentiated cells and complex life cycle would have had many more genes than a single-celled organism like Chlamydomonas. But that turns out not to be the case.

How to explain this apparent paradox? My guess is that just as we have seen in the evolution of animals, we are seeing here that the evolution of organismic complexity is not so much a matter of the evolution of new genes but rather the evolution of changes in the control elements (promoters and enhancers) that dictate how and where the basic tool kit of eukaryotic genes will be expressed .

The evidence is compelling that all these organisms are close relatives; that is, belong to the same clade. They illustrate how colonial forms could arise from unicellular ones and multicellular forms from colonial ones.

The Last Universal Common Ancestor (LUCA)?

Creating Life?

When I headed off to college (in 1949), I wrote an essay speculating on the possibility that some day we would be able to create a living organism from nonliving ingredients. By the time I finished my formal studies in biology — having learned of the incredible complexity of even the simplest organism — I concluded that such a feat could never be accomplished.

Now I'm not so sure.

Several recent advances suggest that we may be getting close to creating life. (But note that these examples represent laboratory manipulations that do not necessarily reflect what may have happened when life first appeared.)

The ability to created membrane-enclosed vesicles that can take in small molecules and assemble them into polymers which remain within the "cell".
The ability to assemble functional ribosomes — the structures that convert the information encoded in the genome into the proteins that run life — from their components.

Could this be placed in the cytoplasm of a living cell and run it?

The same team showed in the previous year (see Science 3 August 2007) that they could insert an entire chromosome from one species of mycoplasma into the cytoplasm of a related species and, in due course, the recipient lost its own chromosome (perhaps destroyed by restriction enzymes encoded by the donor chromosome) and began expressing the phenotype of the donor. In short, they had changed one species into another. But the donor chromosome was made by the donor bacterium, not synthesized in the laboratory. However, there should be no serious obstacle to achieving the same genome transplantation with a chemically-synthesized chromosome.

They've done it! The same team reported on 20 May 2010 in the online Science Express that they had successfully transplanted a completely synthetic genome — based on that of Mycoplasma mycoides — into the related species Mycoplasma capricolum . The recipient strain grew well and soon acquired the phenotype of the M. mycoides donor.

Their procedure:

Chemically synthesize 69- to 79-nt oligonucleotides representing all the stretches of the known chromosome 9 sequence (which contains 316,617 base pairs) except for certain sequences such as transposons, many introns, and transfer RNA genes. In addition new, non-native, sequences such as loxP sites were included to aid future manipulations of the genome.
Stitch these together into blocks of ~750 base pairs. This step was done in vitro by undergraduates enrolled in the "Build A Genome" class at Johns Hopkins.
Introduce these into yeast cells which ligated them into stretches of DNA containing 2–4 thousand base pairs.
Introduce these stepwise into yeast cells so that they replace the equivalent portions of the native chromosome.
The result: a strain of yeast that grows just as well with its new artificial chromosome (now containing only 272,871 base pairs) as it did before.

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The Meaning of Life

Many major historical figures in philosophy have provided an answer to the question of what, if anything, makes life meaningful, although they typically have not put it in these terms (with such talk having arisen only in the past 250 years or so, on which see Landau 1997). Consider, for instance, Aristotle on the human function, Aquinas on the beatific vision, and Kant on the highest good. Relatedly, think about Koheleth, the presumed author of the Biblical book Ecclesiastes, describing life as “futility” and akin to “the pursuit of wind,” Nietzsche on nihilism, as well as Schopenhauer when he remarks that whenever we reach a goal we have longed for we discover “how vain and empty it is.” While these concepts have some bearing on happiness and virtue (and their opposites), they are straightforwardly construed (roughly) as accounts of which highly ranked purposes a person ought to realize that would make her life significant (if any would).

Despite the venerable pedigree, it is only since the 1980s or so that a distinct field of the meaning of life has been established in Anglo-American-Australasian philosophy, on which this survey focuses, and it is only in the past 20 years that debate with real depth and intricacy has appeared. Two decades ago analytic reflection on life’s meaning was described as a “backwater” compared to that on well-being or good character, and it was possible to cite nearly all the literature in a given critical discussion of the field (Metz 2002). Neither is true any longer. Anglo-American-Australasian philosophy of life’s meaning has become vibrant, such that there is now way too much literature to be able to cite comprehensively in this survey. To obtain focus, it tends to discuss books, influential essays, and more recent works, and it leaves aside contributions from other philosophical traditions (such as the Continental or African) and from non-philosophical fields (e.g., psychology or literature). This survey’s central aim is to acquaint the reader with current analytic approaches to life’s meaning, sketching major debates and pointing out neglected topics that merit further consideration.

When the topic of the meaning of life comes up, people tend to pose one of three questions: “What are you talking about?”, “What is the meaning of life?”, and “Is life in fact meaningful?”. The literature on life's meaning composed by those working in the analytic tradition (on which this entry focuses) can be usefully organized according to which question it seeks to answer. This survey starts off with recent work that addresses the first, abstract (or “meta”) question regarding the sense of talk of “life’s meaning,” i.e., that aims to clarify what we have in mind when inquiring into the meaning of life (section 1). Afterward, it considers texts that provide answers to the more substantive question about the nature of meaningfulness (sections 2–3). There is in the making a sub-field of applied meaning that parallels applied ethics, in which meaningfulness is considered in the context of particular cases or specific themes. Examples include downshifting (Levy 2005), implementing genetic enhancements (Agar 2013), making achievements (Bradford 2015), getting an education (Schinkel et al. 2015), interacting with research participants (Olson 2016), automating labor (Danaher 2017), and creating children (Ferracioli 2018). In contrast, this survey focuses nearly exclusively on contemporary normative-theoretical approaches to life’s meanining, that is, attempts to capture in a single, general principle all the variegated conditions that could confer meaning on life. Finally, this survey examines fresh arguments for the nihilist view that the conditions necessary for a meaningful life do not obtain for any of us, i.e., that all our lives are meaningless (section 4).

1. The Meaning of “Meaning”

2.1. god-centered views, 2.2. soul-centered views, 3.1. subjectivism, 3.2. objectivism, 3.3. rejecting god and a soul, 4. nihilism, works cited, classic works, collections, books for the general reader, other internet resources, related entries.

One of the field's aims consists of the systematic attempt to identify what people (essentially or characteristically) have in mind when they think about the topic of life’s meaning. For many in the field, terms such as “importance” and “significance” are synonyms of “meaningfulness” and so are insufficiently revealing, but there are those who draw a distinction between meaningfulness and significance (Singer 1996, 112–18; Belliotti 2019, 145–50, 186). There is also debate about how the concept of a meaningless life relates to the ideas of a life that is absurd (Nagel 1970, 1986, 214–23; Feinberg 1980; Belliotti 2019), futile (Trisel 2002), and not worth living (Landau 2017, 12–15; Matheson 2017).

A useful way to begin to get clear about what thinking about life’s meaning involves is to specify the bearer. Which life does the inquirer have in mind? A standard distinction to draw is between the meaning “in” life, where a human person is what can exhibit meaning, and the meaning “of” life in a narrow sense, where the human species as a whole is what can be meaningful or not. There has also been a bit of recent consideration of whether animals or human infants can have meaning in their lives, with most rejecting that possibility (e.g., Wong 2008, 131, 147; Fischer 2019, 1–24), but a handful of others beginning to make a case for it (Purves and Delon 2018; Thomas 2018). Also under-explored is the issue of whether groups, such as a people or an organization, can be bearers of meaning, and, if so, under what conditions.

Most analytic philosophers have been interested in meaning in life, that is, in the meaningfulness that a person’s life could exhibit, with comparatively few these days addressing the meaning of life in the narrow sense. Even those who believe that God is or would be central to life’s meaning have lately addressed how an individual’s life might be meaningful in virtue of God more often than how the human race might be. Although some have argued that the meaningfulness of human life as such merits inquiry to no less a degree (if not more) than the meaning in a life (Seachris 2013; Tartaglia 2015; cf. Trisel 2016), a large majority of the field has instead been interested in whether their lives as individual persons (and the lives of those they care about) are meaningful and how they could become more so.

Focusing on meaning in life, it is quite common to maintain that it is conceptually something good for its own sake or, relatedly, something that provides a basic reason for action (on which see Visak 2017). There are a few who have recently suggested otherwise, maintaining that there can be neutral or even undesirable kinds of meaning in a person’s life (e.g., Mawson 2016, 90, 193; Thomas 2018, 291, 294). However, these are outliers, with most analytic philosophers, and presumably laypeople, instead wanting to know when an individual’s life exhibits a certain kind of final value (or non-instrumental reason for action).

Another claim about which there is substantial consensus is that meaningfulness is not all or nothing and instead comes in degrees, such that some periods of life are more meaningful than others and that some lives as a whole are more meaningful than others. Note that one can coherently hold the view that some people’s lives are less meaningful (or even in a certain sense less “important”) than others, or are even meaningless (unimportant), and still maintain that people have an equal standing from a moral point of view. Consider a consequentialist moral principle according to which each individual counts for one in virtue of having a capacity for a meaningful life, or a Kantian approach according to which all people have a dignity in virtue of their capacity for autonomous decision-making, where meaning is a function of the exercise of this capacity. For both moral outlooks, we could be required to help people with relatively meaningless lives.

Yet another relatively uncontroversial element of the concept of meaningfulness in respect of individual persons is that it is logically distinct from happiness or rightness (emphasized in Wolf 2010, 2016). First, to ask whether someone’s life is meaningful is not one and the same as asking whether her life is pleasant or she is subjectively well off. A life in an experience machine or virtual reality device would surely be a happy one, but very few take it to be a prima facie candidate for meaningfulness (Nozick 1974: 42–45). Indeed, a number would say that one’s life logically could become meaningful precisely by sacrificing one’s well-being, e.g., by helping others at the expense of one’s self-interest. Second, asking whether a person’s existence over time is meaningful is not identical to considering whether she has been morally upright; there are intuitively ways to enhance meaning that have nothing to do with right action or moral virtue, such as making a scientific discovery or becoming an excellent dancer. Now, one might argue that a life would be meaningless if, or even because, it were unhappy or immoral, but that would be to posit a synthetic, substantive relationship between the concepts, far from indicating that speaking of “meaningfulness” is analytically a matter of connoting ideas regarding happiness or rightness. The question of what (if anything) makes a person’s life meaningful is conceptually distinct from the questions of what makes a life happy or moral, although it could turn out that the best answer to the former question appeals to an answer to one of the latter questions.

Supposing, then, that talk of “meaning in life” connotes something good for its own sake that can come in degrees and that is not analytically equivalent to happiness or rightness, what else does it involve? What more can we say about this final value, by definition? Most contemporary analytic philosophers would say that the relevant value is absent from spending time in an experience machine (but see Goetz 2012 for a different view) or living akin to Sisyphus, the mythic figure doomed by the Greek gods to roll a stone up a hill for eternity (famously discussed by Albert Camus and Taylor 1970). In addition, many would say that the relevant value is typified by the classic triad of “the good, the true, and the beautiful” (or would be under certain conditions). These terms are not to be taken literally, but instead are rough catchwords for beneficent relationships (love, collegiality, morality), intellectual reflection (wisdom, education, discoveries), and creativity (particularly the arts, but also potentially things like humor or gardening).

Pressing further, is there something that the values of the good, the true, the beautiful, and any other logically possible sources of meaning involve? There is as yet no consensus in the field. One salient view is that the concept of meaning in life is a cluster or amalgam of overlapping ideas, such as fulfilling higher-order purposes, meriting substantial esteem or admiration, having a noteworthy impact, transcending one’s animal nature, making sense, or exhibiting a compelling life-story (Markus 2003; Thomson 2003; Metz 2013, 24–35; Seachris 2013, 3–4; Mawson 2016). However, there are philosophers who maintain that something much more monistic is true of the concept, so that (nearly) all thought about meaningfulness in a person’s life is essentially about a single property. Suggestions include being devoted to or in awe of qualitatively superior goods (Taylor 1989, 3–24), transcending one’s limits (Levy 2005), or making a contribution (Martela 2016).

Recently there has been something of an “interpretive turn” in the field, one instance of which is the strong view that meaning-talk is logically about whether and how a life is intelligible within a wider frame of reference (Goldman 2018, 116–29; Seachris 2019; Thomas 2019; cf. Repp 2018). According to this approach, inquiring into life’s meaning is nothing other than seeking out sense-making information, perhaps a narrative about life or an explanation of its source and destiny. This analysis has the advantage of promising to unify a wide array of uses of the term “meaning.” However, it has the disadvantages of being unable to capture the intuitions that meaning in life is essentially good for its own sake (Landau 2017, 12–15), that it is not logically contradictory to maintain that an ineffable condition is what confers meaning on life (as per Cooper 2003, 126–42; Bennett-Hunter 2014; Waghorn 2014), and that often human actions themselves (as distinct from an interpretation of them), such as rescuing a child from a burning building, are what bear meaning.

Some thinkers have suggested that a complete analysis of the concept of life’s meaning should include what has been called “anti-matter” (Metz 2002, 805–07, 2013, 63–65, 71–73) or “anti-meaning” (Campbell and Nyholm 2015; Egerstrom 2015), conditions that reduce the meaningfulness of a life. The thought is that meaning is well represented by a bipolar scale, where there is a dimension of not merely positive conditions, but also negative ones. Gratuitous cruelty or destructiveness are prima facie candidates for actions that not merely fail to add meaning, but also subtract from any meaning one’s life might have had.

Despite the ongoing debates about how to analyze the concept of life’s meaning (or articulate the definition of the phrase “meaning in life”), the field remains in a good position to make progress on the other key questions posed above, viz., of what would make a life meaningful and whether any lives are in fact meaningful. A certain amount of common ground is provided by the point that meaningfulness at least involves a gradient final value in a person’s life that is conceptually distinct from happiness and rightness, with exemplars of it potentially being the good, the true, and the beautiful. The rest of this discussion addresses philosophical attempts to capture the nature of this value theoretically and to ascertain whether it exists in at least some of our lives.

2. Supernaturalism

Most analytic philosophers writing on meaning in life have been trying to develop and evaluate theories, i.e., fundamental and general principles, that are meant to capture all the particular ways that a life could obtain meaning. As in moral philosophy, there are recognizable “anti-theorists,” i.e., those who maintain that there is too much pluralism among meaning conditions to be able to unify them in the form of a principle (e.g., Kekes 2000; Hosseini 2015). Arguably, though, the systematic search for unity is too nascent to be able to draw a firm conclusion about whether it is available.

The theories are standardly divided on a metaphysical basis, that is, in terms of which kinds of properties are held to constitute the meaning. Supernaturalist theories are views according to which a spiritual realm is central to meaning in life. Most Western philosophers have conceived of the spiritual in terms of God or a soul as commonly understood in the Abrahamic faiths (but see Mulgan 2015 for discussion of meaning in the context of a God uninterested in us). In contrast, naturalist theories are views that the physical world as known particularly well by the scientific method is central to life’s meaning.

There is logical space for a non-naturalist theory, according to which central to meaning is an abstract property that is neither spiritual nor physical. However, only scant attention has been paid to this possibility in the recent Anglo-American-Australasian literature (Audi 2005).

It is important to note that supernaturalism, a claim that God (or a soul) would confer meaning on a life, is logically distinct from theism, the claim that God (or a soul) exists. Although most who hold supernaturalism also hold theism, one could accept the former without the latter (as Camus more or less did), committing one to the view that life is meaningless or at least lacks substantial meaning. Similarly, while most naturalists are atheists, it is not contradictory to maintain that God exists but has nothing to do with meaning in life or perhaps even detracts from it. Although these combinations of positions are logically possible, some of them might be substantively implausible. The field could benefit from discussion of the comparative attractiveness of various combinations of evaluative claims about what would make life meaningful and metaphysical claims about whether spiritual conditions exist.

Over the past 15 years or so, two different types of supernaturalism have become distinguished on a regular basis (Metz 2019). That is true not only in the literature on life’s meaning, but also in that on the related pro-theism/anti-theism debate, about whether it would be desirable for God or a soul to exist (e.g., Kahane 2011; Kraay 2018; Lougheed 2020). On the one hand, there is extreme supernaturalism, according to which spiritual conditions are necessary for any meaning in life. If neither God nor a soul exists, then, by this view, everyone’s life is meaningless. On the other hand, there is moderate supernaturalism, according to which spiritual conditions are necessary for a great or ultimate meaning in life, although not meaning in life as such. If neither God nor a soul exists, then, by this view, everyone’s life could have some meaning, or even be meaningful, but no one’s life could exhibit the most desirable meaning. For a moderate supernaturalist, God or a soul would substantially enhance meaningfulness or be a major contributory condition for it.

There are a variety of ways that great or ultimate meaning has been described, sometimes quantitatively as “infinite” (Mawson 2016), qualitatively as “deeper” (Swinburne 2016), relationally as “unlimited” (Nozick 1981, 618–19; cf. Waghorn 2014), temporally as “eternal” (Cottingham 2016), and perspectivally as “from the point of view of the universe” (Benatar 2017). There has been no reflection as yet on the crucial question of how these distinctions might bear on each another, for instance, on whether some are more basic than others or some are more valuable than others.

Cross-cutting the extreme/moderate distinction is one between God-centered theories and soul-centered ones. According to the former, some kind of connection with God (understood to be a spiritual person who is all-knowing, all-good, and all-powerful and who is the ground of the physical universe) constitutes meaning in life, even if one lacks a soul (construed as an immortal, spiritual substance that contains one’s identity). In contrast, by the latter, having a soul and putting it into a certain state is what makes life meaningful, even if God does not exist. Many supernaturalists of course believe that God and a soul are jointly necessary for a (greatly) meaningful existence. However, the simpler view, that only one of them is necessary, is common, and sometimes arguments proffered for the complex view fail to support it any more than the simpler one.

The most influential God-based account of meaning in life has been the extreme view that one’s existence is significant if and only if one fulfills a purpose God has assigned. The familiar idea is that God has a plan for the universe and that one’s life is meaningful just to the degree that one helps God realize this plan, perhaps in a particular way that God wants one to do so. If a person failed to do what God intends her to do with her life (or if God does not even exist), then, on the current view, her life would be meaningless.

Thinkers differ over what it is about God’s purpose that might make it uniquely able to confer meaning on human lives, but the most influential argument has been that only God’s purpose could be the source of invariant moral rules (Davis 1987, 296, 304–05; Moreland 1987, 124–29; Craig 1994/2013, 161–67) or of objective values more generally (Cottingham 2005, 37–57), where a lack of such would render our lives nonsensical. According to this argument, lower goods such as animal pleasure or desire satisfaction could exist without God, but higher ones pertaining to meaning in life, particularly moral virtue, could not. However, critics point to many non-moral sources of meaning in life (e.g., Kekes 2000; Wolf 2010), with one arguing that a universal moral code is not necessary for meaning in life, even if, say, beneficent actions are (Ellin 1995, 327). In addition, there are a variety of naturalist and non-naturalist accounts of objective morality––and of value more generally––on offer these days, so that it is not clear that it must have a supernatural source in God’s will.

One recurrent objection to the idea that God’s purpose could make life meaningful is that if God had created us with a purpose in mind, then God would have degraded us and thereby undercut the possibility of us obtaining meaning from fulfilling the purpose. The objection harks back to Jean-Paul Sartre, but in the analytic literature it appears that Kurt Baier was the first to articulate it (1957/2000, 118–20; see also Murphy 1982, 14–15; Singer 1996, 29; Kahane 2011; Lougheed 2020, 121–41). Sometimes the concern is the threat of punishment God would make so that we do God’s bidding, while other times it is that the source of meaning would be constrictive and not up to us, and still other times it is that our dignity would be maligned simply by having been created with a certain end in mind (for some replies to such concerns, see Hanfling 1987, 45–46; Cottingham 2005, 37–57; Lougheed 2020, 111–21).

There is a different argument for an extreme God-based view that focuses less on God as purposive and more on God as infinite, unlimited, or ineffable, which Robert Nozick first articulated with care (Nozick 1981, 594–618; see also Bennett-Hunter 2014; Waghorn 2014). The core idea is that for a finite condition to be meaningful, it must obtain its meaning from another condition that has meaning. So, if one’s life is meaningful, it might be so in virtue of being married to a person, who is important. Being finite, the spouse must obtain his or her importance from elsewhere, perhaps from the sort of work he or she does. This work also must obtain its meaning by being related to something else that is meaningful, and so on. A regress on meaningful conditions is present, and the suggestion is that the regress can terminate only in something so all-encompassing that it need not (indeed, cannot) go beyond itself to obtain meaning from anything else. And that is God. The standard objection to this relational rationale is that a finite condition could be meaningful without obtaining its meaning from another meaningful condition. Perhaps it could be meaningful in itself, without being connected to something beyond it, or maybe it could obtain its meaning by being related to something else that is beautiful or otherwise valuable for its own sake but not meaningful (Nozick 1989, 167–68; Thomson 2003, 25–26, 48).

A serious concern for any extreme God-based view is the existence of apparent counterexamples. If we think of the stereotypical lives of Albert Einstein, Mother Teresa, and Pablo Picasso, they seem meaningful even if we suppose there is no all-knowing, all-powerful, and all-good spiritual person who is the ground of the physical world (e.g., Wielenberg 2005, 31–37, 49–50; Landau 2017). Even religiously inclined philosophers have found this hard to deny these days (Quinn 2000, 58; Audi 2005; Mawson 2016, 5; Williams 2020, 132–34).

Largely for that reason, contemporary supernaturalists have tended to opt for moderation, that is, to maintain that God would greatly enhance the meaning in our lives, even if some meaning would be possible in a world without God. One approach is to invoke the relational argument to show that God is necessary, not for any meaning whatsoever, but rather for an ultimate meaning. “Limited transcendence, the transcending of our limits so as to connect with a wider context of value which itself is limited, does give our lives meaning––but a limited one. We may thirst for more” (Nozick 1981, 618). Another angle is to appeal to playing a role in God’s plan, again to claim, not that it is essential for meaning as such, but rather for “a cosmic significance....intead of a significance very limited in time and space” (Swinburne 2016, 154; see also Quinn 2000; Cottingham 2016, 131). Another rationale is that by fulfilling God’s purpose, we would meaningfully please God, a perfect person, as well as be remembered favorably by God forever (Cottingham 2016, 135; Williams 2020, 21–22, 29, 101, 108). Still another argument is that only with God could the deepest desires of human nature be satisfied (e.g., Goetz 2012; Seachris 2013, 20; Cottingham 2016, 127, 136), even if more surface desires could be satisfied without God.

In reply to such rationales for a moderate supernaturalism, there has been the suggestion that it is precisely by virtue of being alone in the universe that our lives would be particularly significant; otherwise, God’s greatness would overshadow us (Kahane 2014). There has also been the response that, with the opportunity for greater meaning from God would also come that for greater anti-meaning, so that it is not clear that a world with God would offer a net gain in respect of meaning (Metz 2019, 34–35). For example, if pleasing God would greatly enhance meaning in our lives, then presumably displeasing God would greatly reduce it and to a comparable degree. In addition, there are arguments for extreme naturalism (or its “anti-theist” cousin) mentioned below (sub-section 3.3).

Notice that none of the above arguments for supernaturalism appeals to the prospect of eternal life (at least not explicitly). Arguments that do make such an appeal are soul-centered, holding that meaning in life mainly comes from having an immortal, spiritual substance that is contiguous with one’s body when it is alive and that will forever outlive its death. Some think of the afterlife in terms of one’s soul entering a transcendent, spiritual realm (Heaven), while others conceive of one’s soul getting reincarnated into another body on Earth. According to the extreme version, if one has a soul but fails to put it in the right state (or if one lacks a soul altogether), then one’s life is meaningless.

There are three prominent arguments for an extreme soul-based perspective. One argument, made famous by Leo Tolstoy, is the suggestion that for life to be meaningful something must be worth doing, that something is worth doing only if it will make a permanent difference to the world, and that making a permanent difference requires being immortal (see also Hanfling 1987, 22–24; Morris 1992, 26; Craig 1994). Critics most often appeal to counterexamples, suggesting for instance that it is surely worth your time and effort to help prevent people from suffering, even if you and they are mortal. Indeed, some have gone on the offensive and argued that helping people is worth the sacrifice only if and because they are mortal, for otherwise they could invariably be compensated in an afterlife (e.g., Wielenberg 2005, 91–94). Another recent and interesting criticism is that the major motivations for the claim that nothing matters now if one day it will end are incoherent (Greene 2021).

A second argument for the view that life would be meaningless without a soul is that it is necessary for justice to be done, which, in turn, is necessary for a meaningful life. Life seems nonsensical when the wicked flourish and the righteous suffer, at least supposing there is no other world in which these injustices will be rectified, whether by God or a Karmic force. Something like this argument can be found in Ecclesiastes, and it continues to be defended (e.g., Davis 1987; Craig 1994). However, even granting that an afterlife is required for perfectly just outcomes, it is far from obvious that an eternal afterlife is necessary for them, and, then, there is the suggestion that some lives, such as Mandela’s, have been meaningful precisely in virtue of encountering injustice and fighting it.

A third argument for thinking that having a soul is essential for any meaning is that it is required to have the sort of free will without which our lives would be meaningless. Immanuel Kant is known for having maintained that if we were merely physical beings, subjected to the laws of nature like everything else in the material world, then we could not act for moral reasons and hence would be unimportant. More recently, one theologian has eloquently put the point in religious terms: “The moral spirit finds the meaning of life in choice. It finds it in that which proceeds from man and remains with him as his inner essence rather than in the accidents of circumstances turns of external fortune....(W)henever a human being rubs the lamp of his moral conscience, a Spirit does appear. This Spirit is God....It is in the ‘Thou must’ of God and man’s ‘I can’ that the divine image of God in human life is contained” (Swenson 1949/2000, 27–28). Notice that, even if moral norms did not spring from God’s commands, the logic of the argument entails that one’s life could be meaningful, so long as one had the inherent ability to make the morally correct choice in any situation. That, in turn, arguably requires something non-physical about one’s self, so as to be able to overcome whichever physical laws and forces one might confront. The standard objection to this reasoning is to advance a compatibilism about having a determined physical nature and being able to act for moral reasons (e.g., Arpaly 2006; Fischer 2009, 145–77). It is also worth wondering whether, if one had to have a spiritual essence in order to make free choices, it would have to be one that never perished.

Like God-centered theorists, many soul-centered theorists these days advance a moderate view, accepting that some meaning in life would be possible without immortality, but arguing that a much greater meaning would be possible with it. Granting that Einstein, Mandela, and Picasso had somewhat meaningful lives despite not having survived the deaths of their bodies (as per, e.g., Trisel 2004; Wolf 2015, 89–140; Landau 2017), there remains a powerful thought: more is better. If a finite life with the good, the true, and the beautiful has meaning in it to some degree, then surely it would have all the more meaning if it exhibited such higher values––including a relationship with God––for an eternity (Cottingham 2016, 132–35; Mawson 2016, 2019, 52–53; Williams 2020, 112–34; cf. Benatar 2017, 35–63). One objection to this reasoning is that the infinity of meaning that would be possible with a soul would be “too big,” rendering it difficult for the moderate supernaturalist to make sense of the intution that a finite life such as Einstein’s can indeed count as meaningful by comparison (Metz 2019, 30–31; cf. Mawson 2019, 53–54). More common, though, is the objection that an eternal life would include anti-meaning of various kinds, such as boredom and repetition, discussed below in the context of extreme naturalism (sub-section 3.3).

3. Naturalism

Recall that naturalism is the view that a physical life is central to life’s meaning, that even if there is no spiritual realm, a substantially meaningful life is possible. Like supernaturalism, contemporary naturalism admits of two distinguishable variants, moderate and extreme (Metz 2019). The moderate version is that, while a genuinely meaningful life could be had in a purely physical universe as known well by science, a somewhat more meaningful life would be possible if a spiritual realm also existed. God or a soul could enhance meaning in life, although they would not be major contributors. The extreme version of naturalism is the view that it would be better in respect of life’s meaning if there were no spiritual realm. From this perspective, God or a soul would be anti-matter, i.e., would detract from the meaning available to us, making a purely physical world (even if not this particular one) preferable.

Cross-cutting the moderate/extreme distinction is that between subjectivism and objectivism, which are theoretical accounts of the nature of meaningfulness insofar as it is physical. They differ in terms of the extent to which the human mind constitutes meaning and whether there are conditions of meaning that are invariant among human beings. Subjectivists believe that there are no invariant standards of meaning because meaning is relative to the subject, i.e., depends on an individual’s pro-attitudes such as her particular desires or ends, which are not shared by everyone. Roughly, something is meaningful for a person if she strongly wants it or intends to seek it out and she gets it. Objectivists maintain, in contrast, that there are some invariant standards for meaning because meaning is at least partly mind-independent, i.e., obtains not merely in virtue of being the object of anyone’s mental states. Here, something is meaningful (partially) because of its intrinsic nature, in the sense of being independent of whether it is wanted or intended; meaning is instead (to some extent) the sort of thing that merits these reactions.

There is logical space for an orthogonal view, according to which there are invariant standards of meaningfulness constituted by what all human beings would converge on from a certain standpoint. However, it has not been much of a player in the field (Darwall 1983, 164–66).

According to this version of naturalism, meaning in life varies from person to person, depending on each one’s variable pro-attitudes. Common instances are views that one’s life is more meaningful, the more one gets what one happens to want strongly, achieves one’s highly ranked goals, or does what one believes to be really important (Trisel 2002; Hooker 2008). One influential subjectivist has recently maintained that the relevant mental state is caring or loving, so that life is meaningful just to the extent that one cares about or loves something (Frankfurt 1988, 80–94, 2004). Another recent proposal is that meaningfulness consists of “an active engagement and affirmation that vivifies the person who has freely created or accepted and now promotes and nurtures the projects of her highest concern” (Belliotti 2019, 183).

Subjectivism was dominant in the middle of the twentieth century, when positivism, noncognitivism, existentialism, and Humeanism were influential (Ayer 1947; Hare 1957; Barnes 1967; Taylor 1970; Williams 1976). However, in the last quarter of the twentieth century, inference to the best explanation and reflective equilibrium became accepted forms of normative argumentation and were frequently used to defend claims about the existence and nature of objective value (or of “external reasons,” ones obtaining independently of one’s extant attitudes). As a result, subjectivism about meaning lost its dominance. Those who continue to hold subjectivism often remain suspicious of attempts to justify beliefs about objective value (e.g., Trisel 2002, 73, 79, 2004, 378–79; Frankfurt 2004, 47–48, 55–57; Wong 2008, 138–39; Evers 2017, 32, 36; Svensson 2017, 54). Theorists are moved to accept subjectivism typically because the alternatives are unpalatable; they are reasonably sure that meaning in life obtains for some people, but do not see how it could be grounded on something independent of the mind, whether it be the natural or the supernatural (or the non-natural). In contrast to these possibilities, it appears straightforward to account for what is meaningful in terms of what people find meaningful or what people want out of their lives. Wide-ranging meta-ethical debates in epistemology, metaphysics, and the philosophy of language are necessary to address this rationale for subjectivism.

There is a cluster of other, more circumscribed arguments for subjectivism, according to which this theory best explains certain intuitive features of meaning in life. For one, subjectivism seems plausible since it is reasonable to think that a meaningful life is an authentic one (Frankfurt 1988, 80–94). If a person’s life is significant insofar as she is true to herself or her deepest nature, then we have some reason to believe that meaning simply is a function of those matters for which the person cares. For another, it is uncontroversial that often meaning comes from losing oneself, i.e., in becoming absorbed in an activity or experience, as opposed to being bored by it or finding it frustrating (Frankfurt 1988, 80–94; Belliotti 2019, 162–70). Work that concentrates the mind and relationships that are engrossing seem central to meaning and to be so because of the subjective elements involved. For a third, meaning is often taken to be something that makes life worth continuing for a specific person, i.e., that gives her a reason to get out of bed in the morning, which subjectivism is thought to account for best (Williams 1976; Svensson 2017; Calhoun 2018).

Critics maintain that these arguments are vulnerable to a common objection: they neglect the role of objective value (or an external reason) in realizing oneself, losing oneself, and having a reason to live (Taylor 1989, 1992; Wolf 2010, 2015, 89–140). One is not really being true to oneself, losing oneself in a meaningful way, or having a genuine reason to live insofar as one, say, successfully maintains 3,732 hairs on one’s head (Taylor 1992, 36), cultivates one’s prowess at long-distance spitting (Wolf 2010, 104), collects a big ball of string (Wolf 2010, 104), or, well, eats one’s own excrement (Wielenberg 2005, 22). The counterexamples suggest that subjective conditions are insufficient to ground meaning in life; there seem to be certain actions, relationships, and states that are objectively valuable (but see Evers 2017, 30–32) and toward which one’s pro-attitudes ought to be oriented, if meaning is to accrue.

So say objectivists, but subjectivists feel the pull of the point and usually seek to avoid the counterexamples, lest they have to bite the bullet by accepting the meaningfulness of maintaining 3,732 hairs on one’s head and all the rest (for some who do, see Svensson 2017, 54–55; Belliotti 2019, 181–83). One important strategy is to suggest that subjectivists can avoid the counterexamples by appealing to the right sort of pro-attitude. Instead of whatever an individual happens to want, perhaps the relevant mental state is an emotional-perceptual one of seeing-as (Alexis 2011; cf. Hosseini 2015, 47–66), a “categorical” desire, that is, an intrinsic desire constitutive of one’s identity that one takes to make life worth continuing (Svensson 2017), or a judgment that one has a good reason to value something highly for its own sake (Calhoun 2018). Even here, though, objectivists will argue that it might “appear that whatever the will chooses to treat as a good reason to engage itself is, for the will, a good reason. But the will itself....craves objective reasons; and often it could not go forward unless it thought it had them” (Wiggins 1988, 136). And without any appeal to objectivity, it is perhaps likely that counterexamples would resurface.

Another subjectivist strategy by which to deal with the counterexamples is the attempt to ground meaningfulness, not on the pro-attitudes of an individual valuer, but on those of a group (Darwall 1983, 164–66; Brogaard and Smith 2005; Wong 2008). Does such an intersubjective move avoid (more of) the counterexamples? If so, does it do so more plausibly than an objective theory?

Objective naturalists believe that meaning in life is constituted at least in part by something physical beyond merely the fact that it is the object of a pro-attitude. Obtaining the object of some emotion, desire, or judgment is not sufficient for meaningfulness, on this view. Instead, there are certain conditions of the material world that could confer meaning on anyone’s life, not merely because they are viewed as meaningful, wanted for their own sake, or believed to be choiceworthy, but instead (at least partially) because they are inherently worthwhile or valuable in themselves.

Morality (the good), enquiry (the true), and creativity (the beautiful) are widely held instances of activities that confer meaning on life, while trimming toenails and eating snow––along with the counterexamples to subjectivism above––are not. Objectivism is widely thought to be a powerful general explanation of these particular judgments: the former are meaningful not merely because some agent (whether it is an individual, her society, or even God) cares about them or judges them to be worth doing, while the latter simply lack significance and cannot obtain it even if some agent does care about them or judge them to be worth doing. From an objective perspective, it is possible for an individual to care about the wrong thing or to be mistaken that something is worthwhile, and not merely because of something she cares about all the more or judges to be still more choiceworthy. Of course, meta-ethical debates about the existence and nature of value are again relevant to appraising this rationale.

Some objectivists think that being the object of a person’s mental states plays no constitutive role in making that person’s life meaningful, although they of course contend that it often plays an instrumental role––liking a certain activity, after all, is likely to motivate one to do it. Relatively few objectivists are “pure” in that way, although consequentialists do stand out as clear instances (e.g., Singer 1995; Smuts 2018, 75–99). Most objectivists instead try to account for the above intuitions driving subjectivism by holding that a life is more meaningful, not merely because of objective factors, but also in part because of propositional attitudes such as cognition, conation, and emotion. Particularly influential has been Susan Wolf’s hybrid view, captured by this pithy slogan: “Meaning arises when subjective attraction meets objective attractiveness” (Wolf 2015, 112; see also Kekes 1986, 2000; Wiggins 1988; Raz 2001, 10–40; Mintoff 2008; Wolf 2010, 2016; Fischer 2019, 9–23; Belshaw 2021, 160–81). This theory implies that no meaning accrues to one’s life if one believes in, is satisfied by, or cares about a project that is not truly worthwhile, or if one takes up a truly worthwhile project but fails to judge it important, be satisfied by it, or care about it. A related approach is that, while subjective attraction is not necessary for meaning, it could enhance it (e.g., Audi 2005, 344; Metz 2013, 183–84, 196–98, 220–25). For instance, a stereotypical Mother Teresa who is bored by and alienated from her substantial charity work might have a somewhat significant existence because of it, even if she would have an even more significant existence if she felt pride in it or identified with it.

There have been several attempts to capture theoretically what all objectively attractive, inherently worthwhile, or finally valuable conditions have in common insofar as they bear on meaning in a person’s life. Over the past few decades, one encounters the proposals that objectively meaningful conditions are just those that involve: positively connecting with organic unity beyond oneself (Nozick 1981, 594–619); being creative (Taylor 1987; Matheson 2018); living an emotional life (Solomon 1993; cf. Williams 2020, 56–78); promoting good consequences, such as improving the quality of life of oneself and others (Singer 1995; Audi 2005; Smuts 2018, 75–99); exercising or fostering rational nature in exceptional ways (Smith 1997, 179–221; Gewirth 1998, 177–82; Metz 2013, 222–36); progressing toward ends that can never be fully realized because one’s knowledge of them changes as one approaches them (Levy 2005); realizing goals that are transcendent for being long-lasting in duration and broad in scope (Mintoff 2008); living virtuously (May 2015, 61–138; McPherson 2020); and loving what is worth loving (Wolf 2016). There is as yet no convergence in the field on one, or even a small cluster, of these accounts.

One feature of a large majority of the above naturalist theories is that they are aggregative or additive, objectionably treating a life as a mere “container” of bits of life that are meaningful considered in isolation from other bits (Brännmark 2003, 330). It has become increasingly common for philosophers of life’s meaning, especially objectivists, to hold that life as a whole, or at least long stretches of it, can substantially affect its meaningfulness beyond the amount of meaning (if any) in its parts.

For instance, a life that has lots of beneficence and otherwise intuitively meaning-conferring conditions but that is also extremely repetitive (à la the movie Groundhog Day ) is less than maximally meaningful (Taylor 1987; Blumenfeld 2009). Furthermore, a life that not only avoids repetition but also ends with a substantial amount of meaningful (or otherwise desirable) parts seems to have more meaning overall than one that has the same amount of meaningful (desirable) parts but ends with few or none of them (Kamm 2013, 18–22; Dorsey 2015). Still more, a life in which its meaningless (or otherwise undesirable parts) cause its meaningful (desirable) parts to come about through a process of personal growth seems meaningful in virtue of this redemptive pattern, “good life-story,” or narrative self-expression (Taylor 1989, 48–51; Wong 2008; Fischer 2009, 145–77; Kauppinen 2012; May 2015, 61–138; Velleman 2015, 141–73). These three cases suggest that meaning can inhere in life as a whole, that is, in the relationships between its parts, and not merely in the parts considered in isolation. However, some would maintain that it is, strictly speaking, the story that is or could be told of a life that matters, not so much the life-story qua relations between events themselves (de Bres 2018).

There are pure or extreme versions of holism present in the literature, according to which the only possible bearer of meaning in life is a person’s life as a whole, and not any isolated activities, relationships, or states (Taylor 1989, 48–51; Tabensky 2003; Levinson 2004). A salient argument for this position is that judgments of the meaningfulness of a part of someone’s life are merely provisional, open to revision upon considering how they fit into a wider perspective. So, for example, it would initially appear that taking an ax away from a madman and thereby protecting innocent parties confers some meaning on one’s life, but one might well revise that judgment upon learning that the intention behind it was merely to steal an ax, not to save lives, or that the madman then took out a machine gun, causing much more harm than his ax would have. It is worth considering how far this sort of case is generalizable, and, if it can be to a substantial extent, whether that provides strong evidence that only life as a whole can exhibit meaningfulness.

Perhaps most objectivists would, at least upon reflection, accept that both the parts of a life and the whole-life relationships among the parts can exhibit meaning. Supposing there are two bearers of meaning in a life, important questions arise. One is whether a certain narrative can be meaningful even if its parts are not, while a second is whether the meaningfulness of a part increases if it is an aspect of a meaningful whole (on which see Brännmark 2003), and a third is whether there is anything revealing to say about how to make tradeoffs between the parts and whole in cases where one must choose between them (Blumenfeld 2009 appears to assign lexical priority to the whole).

Naturalists until recently had been largely concerned to show that meaning in life is possible without God or a soul; they have not spent much time considering how such spiritual conditions might enhance meaning, but have, in moderate fashion, tended to leave that possibility open (an exception is Hooker 2008). Lately, however, an extreme form of naturalism has arisen, according to which our lives would probably, if not unavoidably, have less meaning in a world with God or a soul than in one without. Although such an approach was voiced early on by Baier (1957), it is really in the past decade or so that this “anti-theist” position has become widely and intricately discussed.

One rationale, mentioned above as an objection to the view that God’s purpose constitutes meaning in life, has also been deployed to argue that the existence of God as such would necessarily reduce meaning, that is, would consist of anti-matter. It is the idea that master/servant and parent/child analogies so prominent in the monotheist religious traditions reveal something about our status in a world where there is a qualitatively higher being who has created us with certain ends in mind: our independence or dignity as adult persons would be violated (e.g., Baier 1957/2000, 118–20; Kahane 2011, 681–85; Lougheed 2020, 121–41). One interesting objection to this reasoning has been to accept that God’s existence is necessarily incompatible with the sort of meaning that would come (roughly stated) from being one’s own boss, but to argue that God would also make greater sorts of meaning available, offering a net gain to us (Mawson 2016, 110–58).

Another salient argument for thinking that God would detract from meaning in life appeals to the value of privacy (Kahane 2011, 681–85; Lougheed 2020, 55–110). God’s omniscience would unavoidably make it impossible for us to control another person’s access to the most intimate details about ourselves, which, for some, amounts to a less meaningful life than one with such control. Beyond questioning the value of our privacy in relation to God, one thought-provoking criticism has been to suggest that, if a lack of privacy really would substantially reduce meaning in our lives, then God, qua morally perfect person, would simply avoid knowing everything about us (Tooley 2018). Lacking complete knowledge of our mental states would be compatible with describing God as “omniscient,” so the criticism goes, insofar as that is plausibly understood as having as much knowledge as is morally permissible.

Turn, now, to major arguments for thinking that having a soul would reduce life’s meaning, so that if one wants a maximally meaningful life, one should prefer a purely physical world, or at least one in which people are mortal. First and foremost, there has been the argument that an immortal life could not avoid becoming boring (Williams 1973), rendering life pointless according to many subjective and objective theories. The literature on this topic has become enormous, with the central reply being that immortality need not get boring (for more recent discussions, see Fischer 2009, 79–101, 2019, 117–42; Mawson 2019, 51–52; Williams 2020, 30–41, 123–29; Belshaw 2021, 182–97). However, it might also be worth questioning whether boredom is sufficient for meaninglessness. Suppose, for instance, that one volunteers to be bored so that many others will not be bored; perhaps this would be a meaningful sacrifice to make. Being bored for an eternity would not be blissful or even satisfying, to be sure, but if it served the function of preventing others from being bored for an eternity, would it be meaningful (at least to some degree)? If, as is commonly held, sacrificing one’s life could be meaningful, why not also sacrificing one’s liveliness?

Another reason given to reject eternal life is that it would become repetitive, which would substantially drain it of meaning (Scarre 2007, 54–55; May 2009, 46–47, 64–65, 71; Smuts 2011, 142–44; cf. Blumenfeld 2009). If, as it appears, there are only a finite number of actions one could perform, relationships one could have, and states one could be in during an eternity, one would have to end up doing the same things again. Even though one’s activities might be more valuable than rolling a stone up a hill forever à la Sisyphus, the prospect of doing them over and over again forever is disheartening for many. To be sure, one might not remember having done them before and hence could avoid boredom, but for some philosophers that would make it all the worse, akin to having dementia and forgetting that one has told the same stories. Others, however, still find meaning in such a life (e.g., Belshaw 2021, 197, 205n41).

A third meaning-based argument against immortality invokes considerations of narrative. If the pattern of one’s life as a whole substantially matters, and if a proper pattern would include a beginning, a middle, and an end, it appears that a life that never ends would lack the relevant narrative structure. “Because it would drag on endlessly, it would, sooner or later, just be a string of events lacking all form....With immortality, the novel never ends....How meaningful can such a novel be?” (May 2009, 68, 72; see also Scarre 2007, 58–60). Notice that this objection is distinct from considerations of boredom and repetition (which concern novelty ); even if one were stimulated and active, and even if one found a way not to repeat one’s life in the course of eternity, an immortal life would appear to lack shape. In reply, some reject the idea that a meaningful life must be akin to a novel, and intead opt for narrativity in the form of something like a string of short stories that build on each other (Fischer 2009, 145–77, 2019, 101–16). Others, though, have sought to show that eternity could still be novel-like, deeming the sort of ending that matters to be a function of what the content is and how it relates to the content that came before (e.g., Seachris 2011; Williams 2020, 112–19).

There have been additional objections to immortality as undercutting meaningfulness, but they are prima facie less powerful than the previous three in that, if sound, they arguably show that an eternal life would have a cost, but probably not one that would utterly occlude the prospect of meaning in it. For example, there have been the suggestions that eternal lives would lack a sense of preciousness and urgency (Nussbaum 1989, 339; Kass 2002, 266–67), could not exemplify virtues such as courageously risking one’s life for others (Kass 2002, 267–68; Wielenberg 2005, 91–94), and could not obtain meaning from sustaining or saving others’ lives (Nussbaum 1989, 338; Wielenberg 2005, 91–94). Note that at least the first two rationales turn substantially on the belief in immortality, not quite immortality itself: if one were immortal but forgot that one is or did not know that at all, then one could appreciate life and obtain much of the virtue of courage (and, conversely, if one were not immortal, but thought that one is, then, by the logic of these arguments, one would fail to appreciate limits and be unable to exemplify courage).

The previous two sections addressed theoretical accounts of what would confer meaning on a human person’s life. Although these theories do not imply that some people’s lives are in fact meaningful, that has been the presumption of a very large majority of those who have advanced them. Much of the procedure has been to suppose that many lives have had meaning in them and then to consider in virtue of what they have or otherwise could. However, there are nihilist (or pessimist) perspectives that question this supposition. According to nihilism (pessimism), what would make a life meaningful in principle cannot obtain for any of us.

One straightforward rationale for nihilism is the combination of extreme supernaturalism about what makes life meaningful and atheism about whether a spiritual realm exists. If you believe that God or a soul is necessary for meaning in life, and if you believe that neither is real, then you are committed to nihilism, to the denial that life can have any meaning. Athough this rationale for nihilism was prominent in the modern era (and was more or less Camus’ position), it has been on the wane in analytic philosophical circles, as extreme supernaturalism has been eclipsed by the moderate variety.

The most common rationales for nihilism these days do not appeal to supernaturalism, or at least not explicitly. One cluster of ideas appeals to what meta-ethicists call “error theory,” the view that evaluative claims (in this case about meaning in life, or about morality qua necessary for meaning) characteristically posit objectively real or universally justified values, but that such values do not exist. According to one version, value judgments often analytically include a claim to objectivity but there is no reason to think that objective values exist, as they “would be entities or qualities or relations of a very strange sort, utterly different from anything else in the universe” (Mackie 1977/1990, 38). According to a second version, life would be meaningless if there were no set of moral standards that could be fully justified to all rational enquirers, but it so happens that such standards cannot exist for persons who can always reasonably question a given claim (Murphy 1982, 12–17). According to a third, we hold certain beliefs about the objectivity and universality of morality and related values such as meaning because they were evolutionarily advantageous to our ancestors, not because they are true. Humans have been “deceived by their genes into thinking that there is a distinterested, objective morality binding upon them, which all should obey” (Ruse and Wilson 1986, 179; cf. Street 2015). One must draw on the intricate work in meta-ethics that has been underway for the past several decades in order to appraise these arguments.

In contrast to error-theoretic arguments for nihilism, there are rationales for it accepting that objective values exist but denying that our lives can ever exhibit or promote them so as to obtain meaning. One version of this approach maintains that, for our lives to matter, we must be in a position to add objective value to the world, which we are not since the objective value of the world is already infinite (Smith 2003). The key premises for this view are that every bit of space-time (or at least the stars in the physical universe) have some positive value, that these values can be added up, and that space is infinite. If the physical world at present contains an infinite degree of value, nothing we do can make a difference in terms of meaning, for infinity plus any amount of value remains infinity. One way to question this argument, beyond doubting the value of space-time or stars, is to suggest that, even if one cannot add to the value of the universe, meaning plausibly comes from being the source of certain values.

A second rationale for nihilism that accepts the existence of objective value is David Benatar’s (2006, 18–59) intriguing “asymmetry argument” for anti-natalism, the view that it is immoral to bring new people into existence because doing so would always be on balance bad for them. For Benatar, the bads of existing (e.g., pains) are real disadvantages relative to not existing, while the goods of existing (pleasures) are not real advantages relative to not existing, since there is in the latter state no one to be deprived of them. If indeed the state of not existing is no worse than that of experiencing the benefits of existence, then, since existing invariably brings harm in its wake, it follows that existing is always worse compared to not existing. Although this argument is illustrated with experiential goods and bads, it seems generalizable to non-experiential ones, including meaning in life and anti-matter. The literature on this argument has become large (for a recent collection, see Hauskeller and Hallich 2022).

Benatar (2006, 60–92, 2017, 35–63) has advanced an additional argument for nihilism, one that appeals to Thomas Nagel’s (1986, 208–32) widely discussed analysis of the extremely external standpoint that human persons can take on their lives. There exists, to use Henry Sidgwick’s influential phrase, the “point of view of the universe,” that is, the standpoint that considers a human being’s life in relation to all times and all places. When one takes up this most external standpoint and views one’s puny impact on the world, little of one’s life appears to matter. What one does in a certain society on Earth over 75 years or so just does not amount to much, when considering the billions of temporal years and billions of light-years that make up space-time. Although this reasoning grants limited kinds of meaning to human beings, from a personal, social, or human perspective, Benatar both denies that the greatest sort of meaning––a cosmic one––is available to them and contends that this makes their lives bad, hence the “nihilist” tag. Some have objected that our lives could in fact have a cosmic significance, say, if they played a role in God’s plan (Quinn 2000, 65–66; Swinburne 2016, 154), were the sole ones with a dignity in the universe (Kahane 2014), or engaged in valuable activities that could be appreciated by anyone anywhere anytime (Wolf 2016, 261–62). Others naturally maintain that cosmic significance is irrelevant to appraising a human life, with some denying that it would be a genuine source of meaning (Landau 2017, 93–99), and others accepting that it would be but maintaining that the absence of this good would not count as a bad or merit regret (discussed in Benatar 2017, 56–62; Williams 2020, 108–11).

Finally, a distinguishable source of nihilism concerns the ontological, as distinct from axiological, preconditions for meaning in life. Perhaps most radically, there are those who deny that we have selves. Do we indeed lack selves, and, if we do, is a meaningful life impossible for us (see essays in Caruso and Flanagan 2018; Le Bihan 2019)? Somewhat less radically, there are those who grant that we have selves, but deny that they are in charge in the relevant way. That is, some have argued that we lack self-governance or free will of the sort that is essential for meaning in life, at least if determinism is true (Pisciotta 2013; essays in Caruso and Flanagan 2018). Non-quantum events, including human decisions, appear to be necessited by a prior state of the world, such that none could have been otherwise, and many of our decisions are a product of unconscious neurological mechanisms (while quantum events are of course utterly beyond our control). If none of our conscious choices could have been avoided and all were ultimately necessited by something external to them, perhaps they are insufficient to merit pride or admiration or to constitute narrative authorship of a life. In reply, some maintain that a compatibilism between determinism and moral responsibility applies with comparable force to meaning in life (e.g., Arpaly 2006; Fischer 2009, 145–77), while others contend that incompatibilism is true of moral responsibility but not of meaning (Pereboom 2014).

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How to cite this entry . Preview the PDF version of this entry at the Friends of the SEP Society . Look up topics and thinkers related to this entry at the Internet Philosophy Ontology Project (InPhO). Enhanced bibliography for this entry at PhilPapers , with links to its database.

Delon, N., 2021, “ The Meaning of Life ”, a bibliography on PhilPapers.
Metz, T., 2021, “ Life, Meaning of ”, in Routledge Encyclopedia of Philosophy , E. Mason (ed.).
O’Brien, W., 2021, “ The Meaning of Life: Early Continental and Analytic Perspectives ”, in Internet Encyclopedia of Philosophy , J. Fieser and B. Dowden (eds.).
Seachris, J., 2021, “ Meaning of Life: The Analytic Perspective ”, in Internet Encyclopedia of Philosophy , J. Fieser and B. Dowden (eds.).

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The Earth is estimated to be a little over 4.5 billion years old and organic life is estimated to have existed on Earth for much of that time, with recently discovered fossils of microorganisms dating back to between 3.8 and 4.3 billion years .

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The origin of life , also known as abiogenesis , describes how living organisms first evolved from inorganic matter! The exact process by which this occurred is not yet known, though there are several theories.

We will cover these theories, including some that have been disproven and others that are currently being studied experimentally!

Origin of Life Theories in Biology

Life Arose Spontaneously

The, now disproven , spontaneous theory states that life was produced from inorganic matter , such as mud, in the absence of any reactions . This was a very early theory on the origin of life, championed by Aristotle . Hundreds of years ago, experiments were conducted to determine the validity of this theory.

An experiment in 1668 by a scientist named Francesco Redi (1626-1697) utilized raw meat in order to determine the origin of maggots . He placed raw meat into two jars- one sealed and one unsealed (Fig. 1). He then waited a week and found that no maggots were produced from the sealed jar, but that maggots were found in the unsealed jar. Flies had access to the unsealed jar, thus revealing that maggots were produced from the eggs of flies. Several different experiments by other scientists followed, all providing further evidence that the theory was incorrect.

Origin of Life Theories Francesco Redi's experiment testing the spontaneous theory of life's origin. Study Smarter

The Panspermia Theory of the Origin of Life

The panspermia theory , also known as the extraterrestrial theory , states that life may have begun elsewhere in the universe and brought to Earth via microorganisms present in a meteor or some other method of transportation. Panspermia means “all seeds” or “seeds everywhere”, implying that the seeds of life are present throughout the universe. Three kinds of panspermia have been proposed:

Litho : life is transported throughout space when an impact on one planet causes rocks to be sent into space, moving to other planets in different solar systems.

Ballistic : life is transported throughout space when an impact on one planet causes rocks to be sent into space, moving to other planets within the same solar system (Fig. 2).

Directed : life is spread to other planets and solar systems intentionally by extraterrestrial civilizations with more advanced technology.

Origin of Life Theories The panspermia theory suggests that life arrived on Earth from elsewhere. Study Smarter

Life Began in Ice

It is believed that, billions of years ago, much of the Earth was frozen and covered in thick ice. Such cold temperatures could have allowed for many of the compounds implicated in the formation of life to maintain stability. This stability could have then allowed these compounds to exist for much longer periods of time than under warmer conditions, potentially allowing for reactions to occur and life to emerge.

Life Began in Clay

The clay theory suggests that self-replicating crystals of clay may have given way to the formation of life by trapping molecules and enhancing their ability to replicate and catalyze reactions. This could have resulted in further replication, the emergence of life, and evolution to complex organisms. The theory was first proposed by a scientist named Alexander Graham Cairns-Smith in the 1960s.

The “RNA world” Theory of the Origin of Life

The “RNA world” theory states that life may have begun with molecules of RNA (Ribonucleic acid), which are able to perform self-replication and catalyze reactions. Over time, these molecules evolved to become more complex. This theory has some evidence to support it.

Like DNA, RNA can contain and process genetic information, but it can also catalyze reactions, which DNA cannot. Thus, RNA may have had the ability to independently support organic life. RNA could also, theoretically, pass genetic information down to the following generations and evolve. While the term “RNA world” was first coined by an American scientist named Walter Gilbert in 1986, the theory was originally presented by American biologist Alexander Rich in 1962. The "RNA world" theory is the most widely accepted theory on the origin of life today.

The Oparin-Haldane Theory of the Origin of Life

In 1924 a Russian scientist named Alexander Oparin and, in 1929, an English scientist named J. B. S. Haldane, proposed that life arose from inorganic matter mixed with other compounds (known as the primordial soup ) under an oxygen-deprived (reducing) atmosphere and gradually evolved into more complex organisms over time. This is known as the Oparin-Haldane or heterotrophic theory of the origin of life. They suggested that this inorganic matter may have experienced reactions caused by lightning that resulted in the formation of amino acids and other important building blocks for the formation of life, thus creating the primordial soup. Reactions within this primordial soup could have then allowed for the formation of molecules of greater complexity, such as proteins, and eventually evolution into complex organisms.

The Miller-Urey Experiment

The Miller-Urey experiment was conducted in 1952 in order to test the validity of the Oparin-Haldane theory. The experiment, conducted by chemists Stanley Miller under the supervision of Harold Urey, revealed that the spontaneous production of organic molecules was possible under the oxygen-deprived conditions Oparin and Haldane suggested Earth may have been under at the time of life's origin.

They ended up building an enclosed environment containing heated water and various compounds (which may have been present in the Earth’s atmosphere at the time), and sent electrical currents through it, in order to initiate reactions through simulated lightning (Fig. 3). After a week, they discovered that organic molecules, such as amino acids and lipids, had formed. Although no complex molecules had formed, this experiment did show that such conditions could result in the formation of organic molecules .

Origin of Life Theories Diagram of the Miller-Urey experiments Study Smarter

Unfortunately, it is now believed that the Earth’s atmosphere was not oxygen deprived at the time life emerged , thus rendering the results of Miller-Urey’s experiment questionable in regard to its applicability to life's origins and casting doubt on Oparin-Haldane’s theory, at least the idea that oxygen deprivation played a role. However, since it was shown that organic molecules could indeed form from abiotic matter, this suggests that some portions of the Oparin-Haldane theory could be correct.

Life Began in Deep-Sea Vents

The deep-sea vents theory involves deep-sea hydrothermal vents , which are geologic structures that spew molecules that have abundant hydrogen . Billions of years ago, these molecules may have then clumped together and experienced chemical reactions, which may have resulted in the emergence of life. The world's oldest fossils, containing microorganisms and dating to between 3.8 and 4.3 billion years old, were discovered in hydrothermal vents in Quebec in 2017.

Timeline of Origin of Life Theories

As you can see above, there have been numerous theories on the origin of life. The following (Fig. 4) is a brief timeline looking at the timeline of some of the theories on the origin of life.

Origin of Life Theories A timeline of theories on the origin of life. Study Smarter

Darwin’s Theory of the Origin of Life

While Charles Darwin’s theory of evolution, published in his book On the Origin of Species in 1859, is the scientist’s most famous contribution to science, he also had some ideas concerning the origin of life on Earth. Darwin never published his thoughts on the origin of life in any of his books, but he briefly discussed his ideas on the subject in a letter to naturalist Joseph Dalton Hooker in 1871. In a mere four paragraphs, he proposed that life likely began in a warm pond in which a protein was formed due to chemical processes and, eventually, evolved into more complex organisms.

This theory is, therefore, somewhat similar to the primordial soup theory proposed by Oparin and Haldane. Unfortunately, Darwin’s thoughts were limited by the scientific knowledge of the time , as it was not yet known that proteins were comprised of amino acids, and little was known about genetic processes or cellular structures. Despite this, his thoughts were very prescient, and a high density of chemicals in a small pond would, indeed, require a source of energy, such as light or heat, to drive reactions.

Origin of Life Theories - Key takeaways

The origin of life , also known as abiogenesis, describes how living organisms first evolved from inorganic matter.
The, now disproven, spontaneous theory states that life was produced from inorganic matter, such as mud, in the absence of any reactions.
The panspermia theory , also known as the extraterrestrial theory, states that life may have begun elsewhere in the universe and brought to Earth via microorganisms present in a meteor or some other method of transportation. There are three kinds of panspermia - litho , ballistic , and directed .
The “RNA world” theory states that life may have begun with molecules of RNA (Ribonucleic acid), which are able to perform self-replication and catalyze reactions. Over time, these molecules evolved to become more complex. The "RNA world" theory is the most widely accepted theory on the origin of life today.
The Miller-Urey experiment was conducted in 1952 in order to test the validity of the Oparin-Haldane theory.

Frequently Asked Questions about Origin of Life Theories

--> what is the origin of life.

Studying the origin of life requires understanding how and why certain chemical reactions within inorganic matter could be capable of producing life. This is a cross-disciplinary study, encompassing portions of biology, chemistry, and physics. The “RNA world” theory states that life may have begun with molecules of RNA (Ribonucleic acid), which are able to perform self-replication and catalyze reactions. Over time, these molecules evolved to become more complex. This theory has some evidence to support it. The "RNA world" theory is the most widely accepted theory on the origin of life today.

--> What are the main theories of the origin of life on Earth?

The main theories are the panspermia theory, the theory that life began in ice, the theory that life began in clay, the "RNA world" theory of the origin of life, the Oparin-Haldane theory of the origin of life, and the theory that life began in deep-sea vents.

--> what is the Oparin and Haldane theory

The Oparin-Haldane theory proposes that life arose from inorganic matter mixed with other compounds (known as the primordial soup ) under an oxygen-deprived (reducing) atmosphere and gradually evolved into more complex organisms over time.

--> Which is the most accepted theory of origin of life?

The "RNA world" theory is the most widely accepted theory on the origin of life today.

--> What is the theory of an RNA world?

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Abiogenesis

The extraterrestrial theory

The three kinds of panspermia that have been proposed are...

If life is transported throughout space due to an impact on one planet causing rocks to be sent into space, moving to other planers within the same solar system, this would be called...

Ballistic panspermia

The clay theory suggests that...

Self-replicating crystals of clay may have given way to the formation of life by trapping molecules.

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National Academy of Sciences (US). Science and Creationism: A View from the National Academy of Sciences: Second Edition. Washington (DC): National Academies Press (US); 1999.

Science and Creationism: A View from the National Academy of Sciences: Second Edition.

Hardcopy Version at National Academies Press

The Origin of the Universe, Earth, and Life

The term "evolution" usually refers to the biological evolution of living things. But the processes by which planets, stars, galaxies, and the universe form and change over time are also types of "evolution." In all of these cases there is change over time, although the processes involved are quite different.

In the late 1920s the American astronomer Edwin Hubble made a very interesting and important discovery. Hubble made observations that he interpreted as showing that distant stars and galaxies are receding from Earth in every direction. Moreover, the velocities of recession increase in proportion with distance, a discovery that has been confirmed by numerous and repeated measurements since Hubble's time. The implication of these findings is that the universe is expanding.

Hubble's hypothesis of an expanding universe leads to certain deductions. One is that the universe was more condensed at a previous time. From this deduction came the suggestion that all the currently observed matter and energy in the universe were initially condensed in a very small and infinitely hot mass. A huge explosion, known as the Big Bang, then sent matter and energy expanding in all directions.

This Big Bang hypothesis led to more testable deductions. One such deduction was that the temperature in deep space today should be several degrees above absolute zero. Observations showed this deduction to be correct. In fact, the Cosmic Microwave Background Explorer (COBE) satellite launched in 1991 confirmed that the background radiation field has exactly the spectrum predicted by a Big Bang origin for the universe.

As the universe expanded, according to current scientific understanding, matter collected into clouds that began to condense and rotate, forming the forerunners of galaxies. Within galaxies, including our own Milky Way galaxy, changes in pressure caused gas and dust to form distinct clouds. In some of these clouds, where there was sufficient mass and the right forces, gravitational attraction caused the cloud to collapse. If the mass of material in the cloud was sufficiently compressed, nuclear reactions began and a star was born.

Some proportion of stars, including our sun, formed in the middle of a flattened spinning disk of material. In the case of our sun, the gas and dust within this disk collided and aggregated into small grains, and the grains formed into larger bodies called planetesimals ("very small planets"), some of which reached diameters of several hundred kilometers. In successive stages these planetesimals coalesced into the nine planets and their numerous satellites. The rocky planets, including Earth, were near the sun, and the gaseous planets were in more distant orbits.

The ages of the universe, our galaxy, the solar system, and Earth can be estimated using modem scientific methods. The age of the universe can be derived from the observed relationship between the velocities of and the distances separating the galaxies. The velocities of distant galaxies can be measured very accurately, but the measurement of distances is more uncertain. Over the past few decades, measurements of the Hubble expansion have led to estimated ages for the universe of between 7 billion and 20 billion years, with the most recent and best measurements within the range of 10 billion to 15 billion years.

A disk of dust and gas, appearing as a dark band in this Hubble Space Telescope photograph, bisects a glowing nebula around a very young star in the constellation Taurus. Similar disks can be seen around other nearby stars and are thought to provide the (more...)

The age of the Milky Way galaxy has been calculated in two ways. One involves studying the observed stages of evolution of different-sized stars in globular clusters. Globular clusters occur in a faint halo surrounding the center of the Galaxy, with each cluster containing from a hundred thousand to a million stars. The very low amounts of elements heavier than hydrogen and helium in these stars indicate that they must have formed early in the history of the Galaxy, before large amounts of heavy elements were created inside the initial generations of stars and later distributed into the interstellar medium through supernova explosions (the Big Bang itself created primarily hydrogen and helium atoms). Estimates of the ages of the stars in globular clusters fall within the range of 11 billion to 16 billion years.

A second method for estimating the age of our galaxy is based on the present abundances of several long-lived radioactive elements in the solar system. Their abundances are set by their rates of production and distribution through exploding supernovas. According to these calculations, the age of our galaxy is between 9 billion and 16 billion years. Thus, both ways of estimating the age of the Milky Way galaxy agree with each other, and they also are consistent with the independently derived estimate for the age of the universe.

Radioactive elements occurring naturally in rocks and minerals also provide a means of estimating the age of the solar system and Earth. Several of these elements decay with half lives between 700 million and more than 100 billion years (the half life of an element is the time it takes for half of the element to decay radioactively into another element). Using these time-keepers, it is calculated that meteorites, which are fragments of asteroids, formed between 4.53 billion and 4.58 billion years ago (asteroids are small "planetoids" that revolve around the sun and are remnants of the solar nebula that gave rise to the sun and planets). The same radioactive time-keepers applied to the three oldest lunar samples returned to Earth by the Apollo astronauts yield ages between 4.4 billion and 4.5 billion years, providing minimum estimates for the time since the formation of the moon.

The oldest known rocks on Earth occur in northwestern Canada (3.96 billion years), but well-studied rocks nearly as old are also found in other parts of the world. In Western Australia, zircon crystals encased within younger rocks have ages as old as 4.3 billion years, making these tiny crystals the oldest materials so far found on Earth.

The best estimates of Earth's age are obtained by calculating the time required for development of the observed lead isotopes in Earth's oldest lead ores. These estimates yield 4.54 billion years as the age of Earth and of meteorites, and hence of the solar system.

The origins of life cannot be dated as precisely, but there is evidence that bacteria-like organisms lived on Earth 3.5 billion years ago, and they may have existed even earlier, when the first solid crust formed, almost 4 billion years ago. These early organisms must have been simpler than the organisms living today. Furthermore, before the earliest organisms there must have been structures that one would not call "alive" but that are now components of living things. Today, all living organisms store and transmit hereditary information using two kinds of molecules: DNA and RNA. Each of these molecules is in turn composed of four kinds of subunits known as nucleotides. The sequences of nucleotides in particular lengths of DNA or RNA, known as genes, direct the construction of molecules known as proteins, which in turn catalyze biochemical reactions, provide structural components for organisms, and perform many of the other functions on which life depends. Proteins consist of chains of subunits known as amino acids. The sequence of nucleotides in DNA and RNA therefore determines the sequence of amino acids in proteins; this is a central mechanism in all of biology.

Experiments conducted under conditions intended to resemble those present on primitive Earth have resulted in the production of some of the chemical components of proteins, DNA, and RNA. Some of these molecules also have been detected in meteorites from outer space and in interstellar space by astronomers using radio-telescopes. Scientists have concluded that the "building blocks of life" could have been available early in Earth's history.

An important new research avenue has opened with the discovery that certain molecules made of RNA, called ribozymes, can act as catalysts in modem cells. It previously had been thought that only proteins could serve as the catalysts required to carry out specific biochemical functions. Thus, in the early prebiotic world, RNA molecules could have been "autocatalytic"—that is, they could have replicated themselves well before there were any protein catalysts (called enzymes).

Laboratory experiments demonstrate that replicating autocatalytic RNA molecules undergo spontaneous changes and that the variants of RNA molecules with the greatest autocatalytic activity come to prevail in their environments. Some scientists favor the hypothesis that there was an early "RNA world," and they are testing models that lead from RNA to the synthesis of simple DNA and protein molecules. These assemblages of molecules eventually could have become packaged within membranes, thus making up "protocells"—early versions of very simple cells.

For those who are studying the origin of life, the question is no longer whether life could have originated by chemical processes involving nonbiological components. The question instead has become which of many pathways might have been followed to produce the first cells.

Will we ever be able to identify the path of chemical evolution that succeeded in initiating life on Earth? Scientists are designing experiments and speculating about how early Earth could have provided a hospitable site for the segregation of molecules in units that might have been the first living systems. The recent speculation includes the possibility that the first living cells might have arisen on Mars, seeding Earth via the many meteorites that are known to travel from Mars to our planet.

Of course, even if a living cell were to be made in the laboratory, it would not prove that nature followed the same pathway billions of years ago. But it is the job of science to provide plausible natural explanations for natural phenomena. The study of the origin of life is a very active research area in which important progress is being made, although the consensus among scientists is that none of the current hypotheses has thus far been confirmed. The history of science shows that seemingly intractable problems like this one may become amenable to solution later, as a result of advances in theory, instrumentation, or the discovery of new facts.

Creationist Views of the Origin of the Universe, Earth, and Life

Many religious persons, including many scientists, hold that God created the universe and the various processes driving physical and biological evolution and that these processes then resulted in the creation of galaxies, our solar system, and life on Earth. This belief, which sometimes is termed "theistic evolution," is not in disagreement with scientific explanations of evolution. Indeed, it reflects the remarkable and inspiring character of the physical universe revealed by cosmology, paleontology, molecular biology, and many other scientific disciplines.

The advocates of "creation science" hold a variety of viewpoints. Some claim that Earth and the universe are relatively young, perhaps only 6,000 to 10,000 years old. These individuals often believe that the present physical form of Earth can be explained by "catastrophism," including a worldwide flood, and that all living things (including humans) were created miraculously, essentially in the forms we now find them.

Other advocates of creation science are willing to accept that Earth, the planets, and the stars may have existed for millions of years. But they argue that the various types of organisms, and especially humans, could only have come about with supernatural intervention, because they show "intelligent design."

In this booklet, both these "Young Earth" and "Old Earth" views are referred to as "creationism" or "special creation."

There are no valid scientific data or calculations to substantiate the belief that Earth was created just a few thousand years ago. This document has summarized the vast amount of evidence for the great age of the universe, our galaxy, the solar system, and Earth from astronomy, astrophysics, nuclear physics, geology, geochemistry, and geophysics. Independent scientific methods consistently give an age for Earth and the solar system of about 5 billion years, and an age for our galaxy and the universe that is two to three times greater. These conclusions make the origin of the universe as a whole intelligible, lend coherence to many different branches of science, and form the core conclusions of a remarkable body of knowledge about the origins and behavior of the physical world.

Nor is there any evidence that the entire geological record, with its orderly succession of fossils, is the product of a single universal flood that occurred a few thousand years ago, lasted a little longer than a year, and covered the highest mountains to a depth of several meters. On the contrary, intertidal and terrestrial deposits demonstrate that at no recorded time in the past has the entire planet been under water. Moreover, a universal flood of sufficient magnitude to form the sedimentary rocks seen today, which together are many kilometers thick, would require a volume of water far greater than has ever existed on and in Earth, at least since the formation of the first known solid crust about 4 billion years ago. The belief that Earth's sediments, with their fossils, were deposited in an orderly sequence in a year's time defies all geological observations and physical principles concerning sedimentation rates and possible quantities of suspended solid matter.

Geologists have constructed a detailed history of sediment deposition that links particular bodies of rock in the crust of Earth to particular environments and processes. If petroleum geologists could find more oil and gas by interpreting the record of sedimentary rocks as having resulted from a single flood, they would certainly favor the idea of such a flood, but they do not. Instead, these practical workers agree with academic geologists about the nature of depositional environments and geological time. Petroleum geologists have been pioneers in the recognition of fossil deposits that were formed over millions of years in such environments as meandering rivers, deltas, sandy barrier beaches, and coral reefs.

The example of petroleum geology demonstrates one of the great strengths of science. By using knowledge of the natural world to predict the consequences of our actions, science makes it possible to solve problems and create opportunities using technology. The detailed knowledge required to sustain our civilization could only have been derived through scientific investigation.

The arguments of creationists are not driven by evidence that can be observed in the natural world. Special creation or supernatural intervention is not subjectable to meaningful tests, which require predicting plausible results and then checking these results through observation and experimentation. Indeed, claims of "special creation" reverse the scientific process. The explanation is seen as unalterable, and evidence is sought only to support a particular conclusion by whatever means possible.

Cite this Page National Academy of Sciences (US). Science and Creationism: A View from the National Academy of Sciences: Second Edition. Washington (DC): National Academies Press (US); 1999. The Origin of the Universe, Earth, and Life.
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Theories that Explain the Origin of Life

Several of us are curious about the origin of life including our own existence. There have been several attempts to explain the origin of life on the earth. Several theories, therefore, came up trying to explain the origin of life. Unfortunately, each theory gives a different account of the origin of life. Some of the theories include the special creation theory, Theory of spontaneous generation, and Theory of Chemical Evolution. The theory of special creation, for example, suggests that the origin of life is God. Christians believe that everything on earth including all living creatures was created by God and thus He is the origin of life. Hindus also believe that the God of creation is the origin of life and according to His will God of creation created and brought to existence life. The Sikh believes that using His word of mouth, God brought everything to life and thus He is the origin of life. According to the special creation theory, it does not indicate any changes living creatures undergo in the course of life since creation. The special creation theory is the most popular especially among people of the different faiths.

Evolution Theory and the Origin of Life

Another name for the evolution theory that tries to explain the origin of life is a physic-chemical theory. It is also referred to as a Materialistic theory. Evolution theory was first suggested by a Russian A.I Oparin, who was a scientist. This was in the year 1923. In 1928 English scientist, Haldane proposes the same theory to support the origin of life. However, the two scientists proposed the theory independently. According to the theory of evolution, the chemical ovulation that occurred several years ago, was gradual and slow and was the origin of life. According to the theory, originally the earth surface and the atmosphere existed but are different from what they were. The energy that supported the chemical reactions came from the sun, the lighting and radiated heat from the sun. The theory indicates how spontaneous life generation under the environmental situations was impossible. Originally atmosphere on earth was reducing but not oxidizing.

Spontaneous Theory and the Origin of Life

According to the theory, life arose spontaneously and suddenly from existing other non living materials e.g. Leaves from trees and manure were said to bring forth insects and worms. However, experiments conducted and results led to the theory being disapproved.

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The origin of the first form of life has been an intriguing concept for many years. different theories and experimental proofs were forwarded by different scientists during the time interval. some of these theories were rejected as they failed to provide shreds of evidence while some others were accepted. however, there is no theory that could provide a wholesome view of the origin of life. the following theories have been suggested over the years: 1. theory of special creation- this theory suggests that all the living forms were created as it is by god. different religions have different narratives as fas as this theory is concerned. there is no scientific ground for this theory. 2. theory of spontaneous generation- this theory suggested for the origin of living forms from the non-living or inanimate objects. aristotle, epicurus, vel holmont are some of the supporters. they believed that a slice of rotten meat gave birth to the maggots. this was disapproved. 3. theory of panspermia- this theory suggested by richter in 1865 and proposed that life reached the earth from other cosmic bodies. 4. theory of biochemical evolution or materialistic theory- this theory was suggested by oparin in 1923 and haldane in 1928. it suggested that primitive earth was reducing in nature due to the absence of oxygen and several chemicals condensed together in oceans, warmed by hot temperature, formed a 'primordial' soup' in which the first living cell took its form. several amino acids, nucleic acids, sugars and other organic and inorganic molecules together formed coacervated that were capable of absorbing water and nutrients and perform budding. these kept on uniting with more and more molecules and formed the first living cell. the theory of biochemical origin had been experimentally supported by urey and miller, where they developed primitive earth-like conditions by providing lightning, water vapors, and inorganic molecules and obtained the organic molecules. hence, it can be concluded that a little insight exists about the origin of life but there are still more possibilities to explore. with the advancement in scientific technologies, there are chances of gathering more pieces of evidence in this regard..

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Defining life and evolution: Essay on the origin, expansion, and evolution of living matter

Affiliation.

1 Institute of Molecular Biology and Genetics of the National Academy of Sciences of Ukraine, Kyiv, 03143, Ukraine. Electronic address: [email protected].
PMID: 34352326
DOI: 10.1016/j.biosystems.2021.104500

This essay aims to define the origin, expansion, and evolution of living matter. The first formations, identified as remains, fossils, traces etc. of life are almost as old as the Earth itself. During four billion years, life on the Earth has continuously existed and been implemented in the range of conditions, ensuring the liquid state of water. During the entire period of life existence, its evolution was proceeding with the tendency of multidirectionality, after each catastrophe tending to the diversity and vastness of distribution, and all the currently living species, regardless of their complexity, have the same evolutionary age. The property of reproductive surplus (multiplication) is inherent in all the living matter. The reproduction of all the living matter is implemented via the "development" - a process of continuous occurrence of something new that did not exist in the previous moment in the reproduced individual at each specific moment of time with the tendency towards the reproduction of a "copy". In its fundamental basis, Life is based on a programme, its material support is implemented and exists not in the field of causative-consecutive events, but in the field of programmed-causative-consecutive events. This predetermines the "biology laws", the behaviour of the material constituent of Life at each time period, and the future of the material constituent of life.

Keywords: Development; Evolution; Genetic program; Origin of life; biological Complexity.

Biological Evolution*
Biology / methods
Earth, Planet
Evolution, Chemical*
Extraterrestrial Environment
Models, Biological
Origin of Life*
Reproduction / physiology
Time Factors

Home / Essay Samples / Science / Evolution / The Origins of Life: Debating Evolution and Divine Creation Theory

The Origins of Life: Debating Evolution and Divine Creation Theory

Category: Religion , Science
Topic: Biblical Worldview , Christian Worldview , Evolution

Pages: 4 (1818 words)

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