Argument from abiogenesis

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For more information, see the Atheist Debates video on What are the odds?.

The argument from abiogenesis concerns the origin of the earlies life forms from non-living matter, known as "abiogenesis". The exact process of abiogenesis is unknown and an ongoing area of research in the chemical sciences. Though many concepts about the beginning of life have been proposed and even demonstrated, and there is a rough framework for the overall stages of the process, as of yet, a standard model of abiogenesis has not been developed.

The term "abiogenesis" was coined in 1870 by Thomas Henry Huxley, an advocate for Charles Darwin's theory of evolution. It comes from the ancient Greek "a-" (not) + "bios" (life) + "genesis" (origin). That is, the origin of life from non-life. Some confusion has arisen from the fact that the term has been used to describe the archaic theory that complex life can arise from non-life, such as maggots growing in meat. This is not the sense in which the word is used by modern researchers. Equivocating the archaic and modern usage in an attempt to discredit a modern theory is a straw man argument.

"If god did not create everything, how did the first single-celled organism originate? By chance?[1]"

Creationists often claim that since abiogenesis could not naturally occur, it required the intervention of a designer.

Abiogenesis vs. evolution[edit]

For more information, see the TalkOrigins Archive article:

Abiogenesis should not be confused with evolution, the study of how living things change over time, or cosmogony, the study of the origin of the universe. While evolution explains how self-replicating entities change over time, abiogenesis is the study of how self-replicators arose in the first place, and how evolution got started. It is thus related to evolution, but distinct.

"Early on [evolution’s current view of]-abiogenesis was an integral part of evolution. [evolution’s current view of]-illusionists thought that 'spontaneous generation' of life would be found to occur everywhere on earth. That was shown to not be the case. [...] They now say that [evolution’s current view of]-abiogenesis is not part of evolution. [2]"

The historic relationship between scientific concepts is irrelevant and (ironically) commits the genetic fallacy. What matters is the current understanding of these concepts. In principle, God could have created simple life and allowed evolutionary processes to take their course, or both both theories could be false, or both true. Attempting to link them, then disprove one to disprove the other is a non sequitur. A typical example of confusion between the two concepts is:

"Many who believe in evolution would tell you that billions of years ago, life began on the edge of an ancient tidal pool or deep in the ocean. [...] If the theory of evolution is true, it should offer a plausible explanation of how the first “simple” cell formed by chance. [...] To sidestep this dilemma, some evolutionary scientists would like to make a distinction between the theory of evolution and the question of the origin of life.[3]"

Yes, they are distinct theories. A theory does not need to describe all phenomena to be considered useful or valid. Apologists like to use the association fallacy to cast doubt on evolution.

Scientific background[edit]

Perhaps the simplest argument for abiogenesis is:

  1. The Earth formerly did not have life.
  2. More recently, life exists on earth.
  3. It is scientific to assume only natural processes occurred.
  4. Therefore, abiogenesis occurred (or possibly panspermia).

Since evidence indicates life arose about 3.7 billion years ago, it is very difficult to find fossil remains of the earliest life forms. Many chemicals thought to have played a part in the origin of life do not last long under the conditions which they may be found today. The rocks where they might otherwise be found might have been contaminated by geologic processes, and many of them may have been subducted into the Earth's mantle. Nonetheless, there are numerous hypotheses as to how life could have arisen.

Some researchers believe that life arose on the surface of the Earth, perhaps as an oily film on the surface of the ocean, or in calmer tidal pools; the surface is, after all, where most living things are found today. Others argue that the surface of the early earth was bombarded with ultraviolet rays that would have broken down organic molecules almost as soon as they were formed, and thus these molecules could not have accumulated in sufficient concentrations to permit interesting reactions to take place.

It is also possible that life arose deep under the ocean, protected from ultraviolet rays, around hydrothermal vents. These could have provided the energy, in the form of heat, necessary for chemicals to form and react with each other.

Some of the chemicals required for life may have fallen to Earth in meteorites. Many chemicals, including sugar and alcohol, can form in gas clouds in outer space, and may therefore have been part of the composition of the Earth from the very beginning of its formation. Others may have fallen to Earth later. Meteorites known as carbonaceous chondrites contain many types of organic molecules, even after falling through the atmosphere and crashing to Earth.

It is hypothesized that minerals, including clays, may have played a role in the origin of life: if certain amino acids become attached to a clay surface, the clay in effect holds them in place, allowing other amino acids to become attached to the original ones.

Other minerals have microscopic pores, which may have been filled with interacting molecules, thus in effect playing the role of a primitive cell wall. However, it is known that lipids can spontaneously form hollow spheres in water. Thus, it is not clear whether metabolism came before cell membranes or vice-versa.

It is possible that we will never know exactly how life arose on Earth, but it may be possible to come up with a handful of likely scenarios.

The Urey-Miller experiment[edit]

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For more information, see the Wikipedia article:

In 1951, Harold Urey and his graduate student Stanley Miller conducted a seminal experiment: they filled a glass vessel with water, methane, ammonia, and hydrogen, by which they hoped to model the ocean and early atmosphere of the Earth (note that today we have a different picture of the composition of the early atmosphere). Two electrodes in the vessel produced sparks, simulating lightning. The vessel was connected by a tube to a condenser and a second chamber, from which samples could be withdrawn and analyzed.

Within a few days, the water turned yellow and dark "muck" had appeared on the walls of the vessel. This turned out to contain glycine, an amino acid. Later on, several other amino acids and other organic molecules were found.

Later experiments not only confirmed the results of the Urey-Miller experiment itself, but expanded on it, showing that many organic molecules are easy to synthesize under a wide variety of conditions, including different atmospheric compositions and energy sources.

Miller and Urey did not create life in the lab, of course, nor does anyone claim that they did. They did, however, demonstrate that molecules essential to living beings can form naturally under likely conditions of early Earth.

Later results[edit]

One common creationist argument is that the Urey-Miller experiment only created a few of the amino acids used by life, not life itself. Another is that the gases used by Miller and Urey were different from those actually present on primordial Earth.

Researchers were able to reanalyze the residues from one of the original experiments, and found several amino acids that instruments in the 1950s were not sensitive enough to detect. [4] In other words, Miller and Urey were more successful than they realized.

The paper also argues that the atmosphere used in that experiment may have been locally realistic. That is, that mixture of gases would not occur throughout the planet, but only near volcanic eruptions.

Later studies during the 1960s by Joan Oró, et al., that used atmospheric conditions that better match the actual (hypothesized) atmosphere of early Earth turned out to give even better results, turning up for example adenine, which is one of the nucleotide bases that form the "backbone" of DNA.

Self replicating machines[edit]

For more information, see the Wikipedia article:

John von Neumann proposed a theoretical self-replicating machine which used surrounding resources to produce further copies of itself. Although different from living cells in many respects, it showed that a relatively simple logical system could propagate itself in an appropriate environment.


For more information, see the Wikipedia article:

Panspermia is a speculative theory that considers life on Earth to have originated elsewhere, developed and arrived on Earth from space. It is an alternate to the abiogenesis theory but still relies on natural processes. The obvious question it raises is where and how did like originate first? This is hard to resolve definitively in the short term because it may require seeking for life elsewhere in the universe. However, it is almost impossible to rule this possibility out, so the argument from abiogenesis will remain in doubt.

If abiogenesis occurred away from Earth and arrived by panspermia, we would not expect to see any evidence of abiogenesis on Earth.

Natural occurrence of many important chemicals[edit]

It is also clear that many substances that are needed for life occur naturally, even in space. [5]


Researchers have found that proteins have properties that may lend themselves to forming functionally useful shapes.

"This is how life, at least the biochemistry of life, could have gotten started [...] Evolution would have optimized the functions, but you don't need that to get started at a low level of efficiency. If you had a soup of our artificial proteins, even with no selection you could at least do low-level biochemistry. [6]"
"Given that such a limited number of binding pockets exist, proteins generated by combining amino acids at random will easily possess the full suite of binding pockets found throughout nature.[7]"

Arguments against abiogenesis[edit]

Personal incredulity[edit]

This argument amounts to "I don't see how abiogenesis could have happened, so it didn't happen". It is an argument from ignorance.

Original replicator is too complex[edit]


Life replicates itself in an either identical or nearly identical form, which distinguishes it from non-living matter. The first replicator, while simpler than modern life forms, was complex and unlikely to occur by chance or natural processes. Therefore, some intelligent intervention was required to get life going.[8]

"The supreme problem for Darwinists is explaining the origin of the first life. For unguided, naturalistic macroevolution to be true, the first life must have generated spontaneously from nonliving chemicals. Unfortunately for Darwinists, the first life-indeed any form of life-is by no means “simple.”[9]"

Leaving aside the issue that "Darwinists" address evolution, not abiogenesis, the apologist has no idea what the first life looked like. How can they claim that it was not simple or even that it was DNA based? This is an argument from ignorance.

Apologists like to compare the original replicator with an amoeba and argue that an amoeba's DNA could not occur by chance, but this is a false analogy because an amoeba is probably nothing like the original replicator.[10]

"Sagan was absolutely convinced that a simple string of prime numbers proves the existence of an intelligent being, but the equivalent of 1,000 encyclopedias in the first one-celled life does not.[9]"
"Researchers have learned that for a cell to survive, at least three different types of complex molecules must work together—DNA (deoxyribonucleic acid), RNA (ribonucleic acid), and proteins.[3]"

The form that the first replicator might have taken and the environment in which it arose is unknown. However, it is almost certain that it was simpler and unlike the functioning of modern cells. It is therefore impossible to claim to any degree of certainty that it is unlikely to have arisen, because estimating the likelihood depends on unknown information. Since the argument fails to rule out other possibilities, it is an argument from ignorance.

"In summary, [...] the inability of modern science to develop a statistically probable mechanism is intriguing, this is not the place for a thoughtful person to wager his faith."

Francis Collins, The Language of God

Necessary cell ingredients cannot exist outside a cell[edit]

"The complex molecules in the simplest living thing cannot reproduce alone. Outside the cell, they break down. Inside the cell, they cannot reproduce without the help of other complex molecules.[3]"
"It turns out that DNA is inherently unstable, and the preservation of genetic information requires a complex symbiotic relationship between the cell and DNA that is so interdependent that neither could have arisen independently of the other.[11]"

While this may be true of modern cells, the first replicator was probably simpler and could use naturally occurring materials. DNA may not have been involved in abiogenesis at all.

No spontaneous generation of complex life[edit]

"Spontaneous generation of life has never been observed[9]"

Creationists often claim that Francesco Redi disproved abiogenesis in 1668 by showing that flies do not appear on meat if the meat is sealed from outside contamination. This idea often manifests in the so-called Peanut Butter argument against evolution. In fact, Redi disproved the theory of spontaneous generation, the idea that fully-formed modern flies spontaneously arise from meat.

After the invention of the microscope by van Leuwenhoek in 1683 and the subsequent discovery of bacteria it was thought that abiogenesis occurred among microscopic creatures. In the nineteenth century, Louis Pasteur sterilized broth by boiling for fifteen minutes and then sealed it in a glass flask. After several months he noticed that dust had settled on the flask, but no micro-organisms had formed within the broth.

The reason that the spontaneous generation of complex life has not been directly observed is that it probably takes millions of years, a wide variety of conditions and circumstances and a planet sized "test sample". Current models of abiogenesis do not claim life can emerge in short periods in small containers.

Of course, scientists have indirectly observed the formation of life in that at one time, the Earth did not exist and life (probably) existed no where else. Now, life exists. Therefore, life spontaneously arose.

Scientists claim they know exactly how abiogenesis occurred[edit]

"Many evolutionists as well as many creationists speak as if they know, beyond any doubt, how the first life came into existence.[9]"

No, scientists or evolutionists don't know yet and they don't claim they do. That is a straw man.

Scientists disagree[edit]

For more information, see the TalkOrigins Archive article:

Apologists claim that scientists disagree over how abiogenesis occurred.

"Other equally respected scientists who also support evolution disagree. [...] Why?[3]"

This demonstrates almost nothing. Almost all scientific theories have controversy surrounding their details. Just because there is controversy, does not imply that they are all mistaken. By arguing that scientists are sometimes wrong, which is an obvious fact, is really a rhetorical technique for poisoning the well.

The argument is related to the teach the controversy movement.

Life always comes from life[edit]

"Life always comes from preexisting life. However, if we go back far enough in time, is it really possible that this fundamental law was broken?[3]"

Making that statement without supporting evidence is begging the question that abiogenesis didn't occur and an argument from incredulity.

No evidence[edit]

Quoting creationist scientists, apologists say:

"no empirical evidence supports the hypotheses of the spontaneous appearance of life on Earth from nothing but a molecular soup, and no significant advance in scientific knowledge leads in this direction[12]"

However, there is some evidence for abiogenesis. The most obvious evidence is that the early Earth was hostile to life and now it contains life.

Regarding the evidence for abiogenesis, we must remember that the event occurred billions of years ago. Also, it probably occurred at a molecular scale. For this reason, we might not expect much direct evidence of abiogenesis. Just because evidence of an event is not available does not make an event impossible. Science is continually progressing may way well discover direct evidence of abiogenesis. Since this argument would collapse completely in that eventually, it is a form of God of the gaps.

Analogy with human design[edit]

Apologists argue that life requires an intelligence to create it.

"If it takes an intelligent entity to create and program a lifeless robot, what would it take to create a living cell, let alone a human? [...] Keeping you out of the cell is a tough, flexible membrane that acts like a brick and mortar wall surrounding a factory.[3]"

This is a false analogy because the first replicator was probably existed on a molecular scale and was much simpler than a robot. Apologists put forward intelligent design as the explanation for life. However this is a poor analogy because cells operate quite differently from human designs.

"No human invention can compete with the technical brilliance evident in even the most basic of cells.[3]"

Human design is the primary example of intelligent design we have (although this risks the spotlight fallacy).

Scientists can only show intelligence creates life[edit]

"if scientists ever did construct a cell, they would accomplish something truly amazing—but would they prove that the cell could be made by accident? If anything, they would prove the very opposite, would they not? [...] whom or what does the scientist who performed the experiment represent? Does he or she represent blind chance or an intelligent entity?[3]"

This misses the point that scientists are trying to replicate the conditions that prevailed during the early Earth. Of course, scientists are involved with performing experiments but the experiments are intended to show that natural processes can produce the key ingredients of life. It is also unreasonable to expect scientists to create life in the lab by simulating natural processes because it most likely requires a vast time scale and a huge (planet sized) experiment.

Counter arguments[edit]

Simple systems can self-replicate[edit]

In certain circumstances, very simple atoms and molecules can self replicate or exhibit structure, such as in crystals or snow flakes. Give that life probably began by simple self-replicating modules, this makes abiogenesis relatively more likely (although it is still hard to determine the probability of abiogenesis in absolute terms).[8]

Plenty of opportunity[edit]

Even if abiogenesis is only a slim possibility, it has plenty of opportunity for that to occur.

There are potentially millions of planets in the habitable zone of stars in our galaxy[13] and there are billions of galaxies. Only considering Earth when considering the likelihood of abiogenesis commits the Texas sharpshooter fallacy.

Experiments that attempt to replicate the conditions of the early Earth find that many important chemicals, such as amino acids, occur naturally without life. The oceans and surface of the Earth is large, providing many opportunities for abiogenesis. Also, planets exist for billions of years; the Earth is already 4.5 billion years old, which gives plenty of opportunities for abiogenesis.

Which God?[edit]

Main Article: Which God?

No specific God or religion is supported by the argument.

What are the odds of God?[edit]

Main Article: Ultimate 747 gambit

The apologist has not provided any evidence that a supernatural cause is possible. At least we have experience of natural causes, which suggests natural causes are possible in principle. No supernatural causes have been observed, so we might conclude the probability of that scenario is zero.

"What they are doing is trying to claim that because something is so incredibly improbable therefore it is impossible by natural means, and that this means that there must be some supernatural means to achieve this, even if they have no examples and no way to demonstrate that a supernatural agent actually exists, or could exist, or that some like of cause outside of nature is possible. So they are taking an incredible improbability, declaring it a virtual impossibility, and then claiming they can resolve this impossibility by appealing to something that they cannot demonstrate is even possible. The probability is essentially zero.[14]"

Appeal to probability[edit]

Even if we accept that abiogenesis is improbable, that does not mean it is impossible that it has occurred by chance. Similarly, if we accept that a God would have a higher probability that he would create life (which is almost impossible to demonstrate), we cannot simply accept that as the explanation. We don't know the events' prior probability (also called its base rate). There may be other explanations that are more probable. For this reason, this argument is sometimes referred to as the lottery fallacy[15] or the base rate fallacy.

"If we were to flip a fair coin, the odds of it landing heads side up is 50%. What if I were to say that 'I want to place his coin down on the ground heads side up.' What are the odds that it's going to be heads side up based on that? Nearly 100%. I could screw up a little bit, I'm not perfect. But it's way better than 50% as to whether I can set a coin on the ground heads side up. So if the argument is 'this is more likely then you should believe it', then every time you find a coin anywhere in the world that is heads side up, you should believe that it was placed there by a thinking person who intentionally placed it heads side up, [and] that is the most plausible explanation. And I think that we all realize that is actually not the case.[16]"

Observations are more consistent with abiogenesis than a designer God[edit]

For our universe, observations fit abiogenesis better than a designer God.

"If there is no God that designed the universe and designed life, first it would mean that life is a chemical accident. It is a very improbable accident that is true. That means for something like that to happen, the universe has to be really old and really big. There's lots of chemistry sets practising and creating molecules before one of them will come up. It's like a lottery: the odds of winning are low but if you have a million people playing, one of them is going to win. So if you see a lottery win, you should expect there are millions of players. And that is the case here. The [universe we would expect] is vastly old and vastly huge. And look, that is the universe we see."

Richard Carrier[17]


See also[edit]