Soup Sham: The Myths of the Miller-Urey Experiment

The Miller-Urey experiment was an experiment done in the 1950's which was claimed to be a big advance relating to the origin of life. The coverage of this experiment in the scientific mainstream is one of the most egregious cases of hype, erroneous information and faulty analysis to be found anywhere in science-related literature. For 65 years mainstream sources have been spouting baloney and incorrect or misleading information on this topic.

The Miller-Urey experiment used a glass apparatus with several different glass chambers connected by tubes. The top glass chamber was filled with a mixture of gases consisting mainly of ammonia and methane. This chamber had an electrical spark unit that continually bombarded these gases with electricity. In his original paper Miller stated, "The discharge was run continuously for a week." If you imagine the electrical sparks coming from a half-severed power line, you will get an idea of how this electrical spark unit worked. The lower chamber consisted of very warm water. After a week of electrical discharges delivered to the gases, amino acids were found in the water of the lower chamber.

The glass apparatus used by the Miller-Urey experiment

For decades this experiment was hailed as something that had shown that “building blocks of life could naturally form,” or that before life appeared there once existed on Earth some "primordial soup" rich in such "building blocks of life." Over the next 65 years, this phrase of “building blocks of life” was constantly used in discussions of the Miller-Urey experiment. But it was never an accurate or appropriate term to be using to describe the amino acids that were produced. The real building blocks of visible organisms are cells, which are built up from the building blocks of protein molecules. The real building blocks of a microscopic microbe are protein molecules, chemical units that usually consist of hundreds of amino acids arranged in just the right way. Amino acids are merely the building blocks of the building blocks of one-celled organisms, and are merely the building blocks of the building blocks of the building blocks of human beings. So it was never accurate to be calling amino acids “building blocks of life.” Calling an amino acid a “building block of life” is as misleading as calling a tiny clay speck “a building block of a house.” Such clay specks are merely the building blocks of a brick, which is a building block of a house.

There is another reason why it is a very misleading analogy to describe amino acids as “building blocks of life.” A building block can be used in any order. If I have a dump truck dump a huge pile of bricks on the lot of my construction site, I can use those bricks in any order to create a brick wall that is the beginning of a house. But amino acids are very different. To make some functional protein, amino acids must be added in just the right order. Shuffle the amino acid sequence of a protein molecule, and you will destroy its functionality. A good and fair analogy would be to compare a protein molecule to an ordered and fine-tuned sequence such as the ordered sequence of characters that make up an essay, a chapter, or a computer program. An amino acid can then be compared to a particular character in such a sequence. Rather than using such a good analogy (appropriate for a case that requires a special arrangement that is an ordered fine-tuned sequence), the science literature has for 65 years used an inappropriate and misleading analogy in which amino acids are compared to building blocks (things that do not require some special arrangement).

Very few of the countless discussions of the Miller-Urey experiment clearly stated the important fact that the experiment had produced amino acids with an equal mixture of right-handed and left-handed amino acids, unlike what is found in earthly organisms. An article in Astrobiology magazine puts it this way:

“A curious aspect of Earth’s life forms is that they contain (with few exceptions) only left-handed amino acids. In contrast, when scientists synthesize amino acids from nonchiral precursors, the result is always a 'racemic' mixture – equal numbers of right- and left-handed forms. Scientists have been unable to perform any experiment that, when starting with conditions believed to emulate those of early Earth, results in a near-total dominance of left-handed amino acids, says George Cody, a geochemist at the Carnegie Institute of Washington.”

Once the Miller-Urey experiment occurred, the world of science literature began to repeat again and again the claim that such an experiment had shown that there must have been some “primordial soup” filled with amino acids. In fact, the experiment actually provided no warrant for any such claim. This is because the experiment had involved week-long continuous electrical bombardment of gases, something that has never occurred in the history of planet Earth.

There is no reason to believe that lightning was any more common in the early Earth than it is today. The chance of someone being hit by lightning is about 1 in 700,000 per year. The chance of a particular man-sized spot being hit twice by lightning in the same year is about 1 in 14,000,000,000,000. But the Miller-Urey experiment used an electrode to provide continuous electricity for a week. During that week, very many thousands of electrical jolts were transmitted into the apparatus. In the history of Earth there has never been any area that got even a millionth of that frequency of electrical stimulation from natural lightning, which lasts for only about 30 millionths of a second when it strikes. The length of electrical stimulation in the Miller-Urey experiment was about 20 billion times longer than the length of time that any natural spot on Earth would have been electrically stimulated by lightning. This by itself is sufficient reason for saying that the Miller-Urey experiment was not a realistic simulation of early Earth conditions. This huge problem with the experiment was ignored by 99% of the treatments of the Miller-Urey experiment in science literature. 

Another reason for doubting the relevancy of the Miller-Urey results is that the electricity was created in a closed glass apparatus chamber. Natural lightning is never created in such a closed environment, but arises instead in the open air, where there is ample opportunity for dissipation of the energy.   

The extreme rarity of amino acids outside of living organisms was another reason for thinking that there could not be any natural non-biological chemistry by which amino acids are created in appreciable amounts, contrary to what the Miller-Urey experiment may have suggested.  As a scientist named Menez stated, "People have predicted the existence of abiotic amino acids from experiments and thermodynamic calculations, but no one has seen them occurring in terrestrial settings, neither in ponds nor in rocks." 

Then there is the issue of the type of gases used in the Miller-Urey experiment. The two scientists used the wrong mixture of gases. They tried to simulate the early earth's atmosphere by using mainly ammonia and methane. But there never was any sound basis for thinking that such gases were the main gases in the early Earth's atmosphere. It is now believed that the early earth's atmosphere was mainly carbon dioxide, nitrogen and water vapor.

A 1965 scientific paper makes clear that there was no basis in that time for thinking that the early earth's atmosphere was mainly methane, ammonia or any mixture of the two. The paper tells us, “The growth of the initial atmosphere and oceans from volcanic discharge seems probable.” The paper then lists some of the contents of volcanic discharges, giving these numbers:

Water vapor: 20-97%

Carbon dioxide: 1-40%

Nitrogen (N₂) : 1-38%

Sulfur dioxide: 0-8%

Hydrogen: 0-4%

Chlorine: 0-4%

The paper also says that methane and ammonia are only emitted by volcanoes in “small quantities.”

Anyone putting such facts together in a kind of “two plus two equals four” way should have realized that it made no sense to assume that the early earth's atmosphere was mainly methane and ammonia. If the earth's atmosphere came mainly from volcanoes, then we clearly should assume that the early earth's atmosphere was mainly the type of gases most commonly emitted by volcanoes (nitrogen, carbon dioxide,  water vapor and sulfur dioxide), and not some gases such as methane and ammonia that are emitted by volcanoes only in “small quantities.”

The facts listed above in the 1965 paper were well known by 1950. So the scientific basis for not believing that the earth's early atmosphere was mainly ammonia and methane was well known by 1950, years before the Miller-Urey experiment. But once the Miller-Urey experiment was done in the 1950's, the world of science literature ignored such very clear reasons for thinking the experiment was of no great relevance. A thousand books and articles hailed the Miller-Urey experiment. Almost all of these writers of these treatments seemed to throw away their critical faculties when dealing with this topic. The writers ignored one very clear and obvious reason for regarding the experiment as irrelevant (the fact that no place on Earth gets anything even a millionth as much as a week of continuous exposure to lightning). They also ignored another clear and obvious reason for rejecting the experiment, that it used the wrong mixture of gases to simulate the early Earth. For 40 years the experts and writers describing the Miller-Urey experiment in enthusiastic tones were like some car buyer who enthusiastically buys a snazzy shiny car, failing to notice heavy smoke and loud noise coming from the engine during the test drive.

Eventually more and more evidence piled up that the gases used by Miller and Urey were not the right mixture. It became more and more evident that the early Earth's atmosphere was a totally different mixture, one corresponding pretty closely to actual outputs of volcanoes (a mixture of mainly nitrogen and carbon dioxide, along with considerable water vapor and sulfur dioxide).

A 2011 press release preserved on a NASA site states the following:  "We can now say with some certainty that many scientists studying the origins of life on Earth simply picked the wrong atmosphere,' said Bruce Watson, Institute Professor of Science at Rensselaer."  The "many scientists" referred to include Miller and Urey.  The press release tells us that the correct atmosphere (derived from a study of volcanic emissions) would have been "an atmosphere dominated by the more oxygen-rich compounds found within our current atmosphere — including water, carbon dioxide, and sulfur dioxide."  A 2007 scientific paper says, "the early Earth is likely to have had a CO2-rich atmosphere, and not a ‘Milley–Urey'’ atmosphere, since at least 4 Ga [4 gigayears] (Canil, 1997; Delano, 2001; Kasting and Catling, 2003)."

Dragging their heels as long as they could, mainstream authorities finally began to eventually let us know (around the year 2010 or so) that the Miller-Urey experiment used the wrong mixture of gases the simulate the early Earth's atmosphere. But they only let us know such a thing decades after they should have told us about this shortcoming. 

Of the experiments using a more suitable mixture of gases to simulate the early Earth's atmosphere, it must be said that none of them have produced a variety of amino acids under conditions realistically simulating the early Earth. In general the methodology of such “Miller-Urey sequel experiments” has been just as objectionable as the Miller-Urey experiment. An example is an experiment that subjected gases to 2 hours of intense proton bombardment. No area on Earth ever received so high a dose of radiation. Another example is an experiment that used strong electrical charges to produce amino acids. Such charges would not have been available in the early Earth.

The situation now is that our mainstream authorities will typically let us know that the Miller-Urey experiment used the wrong gases to simulate the early Earth. But they will typically make such a confession somewhere where it is least likely to be noticed by the reader. It's as if our mainstream writers were still trying to squeeze as much effect from the Miller-Urey experiment as they can, even though the experiment has been debunked. A typical treatment will go like this:

1. The Miller-Urey experiment will be discussed in a way that initially leads the reader to think that it was something indicating that there would have been many amino acids on the early Earth.
2. Somewhere much later in the discussion, it will be mentioned that the Miller-Urey experiment did not use a correct mixture of gases.

Of course, this type of treatment is misleading. It's as misleading as a blog post that tells you in paragraph one that a certain Senator has been accused of murder, and then tells you in paragraph ten that the person making the claim about the murder has admitted that he was merely joking or playing a prank.

An example of this type of treatment is in the Wikipedia.org article on abiogenesis. Near the beginning of the article, we read a statement designed to make the reader think that the Miller-Urey experiment told us something important: “The classic 1952 Miller–Urey experiment and similar research demonstrated that most amino acids, the chemical constituents of the proteins used in all living organisms, can be synthesized from inorganic compounds under conditions intended to replicate those of the early Earth.” Only much, much later in the article do we read about how the Miller-Urey experiment used the wrong mixture of gases to simulate the early earth's atmosphere. It's as if some rule was in operation that our mainstream authorities are still trying to make as many people as possible think that the Miller-Urey experiment helped bolster the idea of a natural origin of life, and that information debunking the experiment must be buried where it is least likely to be noticed. And similarly, a cigarette manufacturer may have 95% of its ad telling you how great its cigarettes are, and only put at the bottom a little box telling you that cigarettes cause cancer.

Then there are the mainstream sources that claim that it doesn't matter that the Miller-Urey experiment used the wrong mixture of gases to simulate the early Earth's atmosphere, on the grounds that similar experiments using the correct mixture have produced similar results. Such claims are about as accurate as someone claiming that it doesn't matter that he got fired from his job, on the grounds that he has “similar methods of producing revenue,” while referring to things such as gathering bottles for cash or begging for money on the street. There has been no experiment realistically simulating early Earth conditions that produced any of the twenty amino acids.

An example of the extremely misleading treatments of the Miller-Urey experiment that we continue to see in the science literature can be found in the recent book Imagined Life by scientists James Trefil and Michael Summers. Here is a statement on page 38 of their book, a statement that is filled with erroneous claims. I will discuss its errors after I quote it.

“Miller-Urey-type experiments have produced virtually every important molecule found in living systems, including stretches of DNA and protein molecules. And surprisingly, even though the consensus is that Miller and Urey had the wrong atmospheric composition in their experiment, it just doesn't matter. Experiments with different atmospheric compositions and different energy sources have produced essentially the same results, albeit with different yields, depending upon the assumed composition of the atmosphere. Furthermore, complex organic molecules (including amino acids) have been found in meteorites, in interstellar dust clouds, and even in debris disks which surround stars and in which exoplanets are forming. Against all expectations, in other words, the basic molecular building blocks of life are common – in fact, they're all over the place.”

Let us carefully examine these statements one by one.

Trefil and Summers statement #1: “Miller-Urey-type experiments have produced virtually every important molecule found in living systems, including stretches of DNA and protein molecules.”

This is one of the most outrageous falsehoods I have ever read in any book. Human beings have roughly 20,000 different types of protein molecules. Not one of them has ever been produced in a “Miller-Urey-type experiment.” No such experiment has ever produced any protein molecule. Miller-Urey-type experiments only produce individual amino acids, and the median number of amino acids in a protein molecule is about 375 amino acids. It is therefore not at all true to say that Miller-Urey type experiments have produced “stretches” of protein molecules, the word "stretch" meaning an "area or expanse." No Miller-Urey-type experiment has ever even produced a nucleotide, which is the basic building block of a DNA molecule (a DNA molecule has billions of nucleotides). So it is utterly false to say that such experiments have produced “stretches of DNA.”

Trefil and Summers statement #2: "And surprisingly, even though the consensus is that Miller and Urey had the wrong atmospheric composition in their experiment, it just doesn't matter. Experiments with different atmospheric compositions and different energy sources have produced essentially the same results, albeit with different yields, depending upon the assumed composition of the atmosphere."

It certainly does matter very much that Miller and Urey “had the wrong atmospheric composition in their experiment,” because such a thing invalidates their whole experiment, making it worthless as a guide to conditions on the early Earth. As for other types of experiments that were inspired by the Miller-Urey experiment, they all have a defect similar to one in the Miller-Urey experiment: they fail to realistically simulate early Earth conditions. Notice that Trefil and Summers merely vaguely refer to "different atmospheric compositions and different energy sources" rather than giving us the details of some specific experiment that realistically simulated early earth conditions and produced amino acids. They cannot give us such specifics because there has never been such an experiment.  

An example of such "Miller-Urey-type" experiments is the one discussed in this paper by Kobayashi and others. They subjected a mixture of carbon monoxide, nitrogen and water to two hours of "high-energy proton irradiation" of 3 million electron volts. This produced spherical micro-structures which yielded amino acids only after hydolysis with hydrogen chloride. Such a technique is not at all a realistic simulation of any conditions on the early Earth. No part of the early Earth was subjected to anything like two hours of high-energy proton bombardment, nor did any part of the early Earth undergo hydrolysis with hydrogen chloride. The authors did not even use a correct mixture of gases corresponding to the mixture believed to have existed on the early Earth, for their mixture used carbon monoxide rather than carbon dioxide. The authors state that a similar proton-bombardment experiment “did not produce amino acids” when a more realistic mixture of gases was used, consisting of carbon dioxide, nitrogen and water.

Another paper sometimes cited as providing "similar results" to the Miller-Urey experiment (but with a realistic mixture of gases) is  the paper "Thermochemical Aspects of the Conversion of the Gaseous System CO₂->N₂->H₂0 Into a Solid Mixture of Amino Acids” by F. Hanic and others.  Such a citation is bogus, because the paper does not describe an attempt to simulate early earth conditions. The method described is quite technological, a  technique depending on electrodes and involving a "high voltage, spontaneously pulsing direct current electric discharge system operating in corona discharge geometry." Such a method involves fancy and specific gadgets, something much more complicated than anything that existed on the early Earth. 

Trefil and Summers statement #3: "Furthermore, complex organic molecules (including amino acids) have been found in meteorites, in interstellar dust clouds, and even in debris disks which surround stars and in which exoplanets are forming. Against all expectations, in other words, the basic molecular building blocks of life are common – in fact, they're all over the place.”

The authors refer to meteorites such as the Murchison meteorite. The claim that amino acids were found in that meteorite (in very small trace amounts) is disputed. The article here in Astrobiology magazine refers to scientists who are skeptical about such a claim, and who suspect that the amino acids detected are due to earthly contamination. No more than trace amounts of  biologically relevant amino acids have been found in meteorites.  For example, we read here that "glycine was the most abundant amino acid" found in the Murchison meteorite, and that it was found in an amount of only 3 parts per million.  

According to the source here, no more than eight of the twenty amino acids used by living things have ever been reported as being detected in meteorites. The traces of amino acids claimed to be deep in the large Murchison meteorite and similar meteorites are biologically irrelevant. Life couldn't start in the dry inside of a meteorite, and if a meteorite broke up catastrophically, any tiny traces of amino acids in it would probably be destroyed. Only one of the 20 amino acids used by living things has been found in an interstellar dust cloud: glycine, the simplest amino acid. The “basic molecular building blocks of life” are proteins, and no protein has ever been detected in outer space. There is no appreciable trace of 19 out of 20 amino acids in outer space. So it was misleading for Trefil and Summers to have said (referring to outer space), “the basic molecular building blocks of life are common – in fact, they're all over the place.”

After telling us on page 38 that "Miller and Urey had the wrong atmospheric composition in their experiment,"  Trefil and Summers on page 95 say, "We described the Miller-Urey experiment, which showed that ordinary chemical processes in Earth's atmosphere could generate the basic molecular building blocks of life."  This is what goes on in the science literature these days: make it look in one place that the Miller-Urey experiment proved something terribly important, but confess in some other place that the experiment had an invalidating defect.  The statement on page 95 by Trefil and Summers was as false as their mythical claim on page 47 that "DNA contains the 'blueprint' of the living thing in which it is found."  DNA merely contains low-level chemical information such as the amino acid sequence of proteins, and (as discussed here) DNA does not contain anything like a blueprint or recipe or algorithm for building either a complete body or any organ or appendage of a body. DNA does not even specify how to make any of the 200 types of cells in the human body, nor does it even specify how to make any of the organelles of such cells. 

So many faulty claims have been discussed or quoted here that the facts should be concisely summarized:

(1) Amino acids are not found in the natural world in appreciable amounts outside of living things. As scientist Menez stated, "No one has seen them occurring in terrestrial settings, neither in ponds nor in rocks." 

(2) No scientific experiment realistically simulating the early Earth has ever produced any of the 20 amino acids used by living things, with the exception of experiments (such as this experiment) producing glycine or alanine (the two simplest amino acids) at trace levels of 40 parts per million, or even smaller amounts. Except for the experiment producing only trace amounts of glycine or alanine, the only experiments attempting to produce amino acids have had one or more major defects, such as not using a realistic mixture of gases to simulate the early Earth's atmosphere, or exposing a sample of gas to utterly unrealistic energy exposures (such as continuous one-week electricity bombardments or 2-day proton beam bombardments) that no area on Earth would have been subjected to. 

(3) The famous Miller-Urey experiment was guility of three such defects: using an inappropriate mixture of gases to simulate the early Earth's atmosphere;  exposing such gases to continuous week-long electricity bombardments many millions of times longer than any spot on Earth would endure from a lightning bolt; and using a glass chamber to confine electricity in a way unlike anything that would occur naturally.

(4) The Miller-Urey experiment did not actually produce amino acids such as found in living things (all left-handed), but instead a mixture in which right-handed amino acids were as common as left-handed amino acids.

(5) Although accounts of the Miller-Urey experiment typically  described amino acids as "building blocks of life," the actual building blocks of microscopic life are proteins, things which typically require extremely specially-ordered arrangements of hundreds of amino acids (unlike houses which do not require that building blocks be used in some special order). 

(7) There is no geological, astronomical or meteorological reason for thinking that amino acids existed in anything other than negligible amounts before life existed, and there is no evidential basis for believing that there ever existed any such thing as a prebiotic "primordial soup" that was rich in either amino acids or the building blocks of DNA (nucleotides). 

For 65 years the mainstream science literature has had coverage of the Miller-Urey experiment that has largely been baloney. Very sadly, the coverage of the Miller-Urey experiment in scientific literature suggests that scientists and science writers will sometimes hype up a misleading pile of runaway praise and inappropriate accolades relating to evidence or arguments or experiments with very glaring defects, when such work seems to offer some result that seems to support some dogma that scientists eagerly wish to believe. 

Postscript: A recent experiment simulating a meteorite collision at 9 kilometers a second has produced the two simplest amino acids used by living things (glycine and alanine), but only in the scantiest of trace amounts (about 1 nanomole, about a ten millionth of a gram). The paper also mentions a retention time of only seconds (Figure 1). Another paper discusses an experiment attempting to simulate "soda fountains" on the early Earth. But the experiment produces only the tiniest trace (one nanomole) of glycine, and 60 nanomoles of alanine. 

The Miller-Urey apparatus included a special "cold trap" that isolated the amino acids created from being disrupted by the energy source. Such a thing does not correspond to anything that existed on the early Earth.  You might realistically simulate Earth conditions by having an outdoor apparatus the size of an Olympic-sized swimming pool, filled with millions of gallons of water.  By having the apparatus outside, you would simulate actual pond conditions,  in which water is partially replaced each month by rainfall and evaporation. With such an experiment, there would never be any concentration of amino acids, and no liter of water would ever have any more than microscopic traces of amino acids. 

A NASA page tells us an additional reason why the Miller-Urey experiment never was a realistic simulation of early Earth conditions. The early Earth was much colder than it is today, because the sun's radiation was much weaker. It is estimated that billions of years ago, the sun's radiation was only 70% of what it is today. What is called the faint young sun paradox is the discrepancy between the weakness of solar radiation billions of years ago and claims that life arose billions of years ago. The NASA page says, "Lightning, which comes from thunderclouds formed by rising warm air, would have been rarer under a 30% dimmer Sun." I explain above why "The length of electrical stimulation in the Miller-Urey experiment was about 20 billion times longer than the length of time that any natural spot on Earth would have been electrically stimulated by lightning." Such a calculation was made before even considering that lightning would have been much rarer in a colder Earth.