Top Five Problems with Current Origin-of-Life Theories
Casey Luskin December 12, 2012 5:01 PM
Last summer I published a list of the "Top Ten Problems with Darwinian Evolution." Since that time, some readers have requested a list of major problems with theories seeking to explain the chemical origin of life. There are numerous problems, but here's my list of the top 5:
Problem 1: No Viable Mechanism to Generate a Primordial Soup.
According to conventional thinking among origin-of-life theorists, life arose via unguided chemical reactions on the early Earth some 3 to 4 billion years ago. Most theorists believe that there were many steps involved in the origin of life, but the very first step would have involved the production of a primordial soup -- a water-based sea of simple organic molecules -- out of which life arose. While the existence of this "soup" has been accepted as unquestioned fact for decades, this first step in most origin-of-life theories faces numerous scientific difficulties.
In 1953, a graduate student at the University of Chicago named Stanley Miller, along with his faculty advisor Harold Urey, performed experiments hoping to produce the building blocks of life under natural conditions on the early Earth.1 These "Miller-Urey experiments" intended to simulate lightning striking the gasses in the early Earth's atmosphere. After running the experiments and letting the chemical products sit for a period of time, Miller discovered that amino acids -- the building blocks of proteins -- had been produced.
For decades, these experiments have been hailed as a demonstration that the "building blocks" of life could have arisen under natural, realistic Earthlike conditions,2 corroborating the primordial soup hypothesis. However, it has also been known for decades that the Earth's early atmosphere was fundamentally different from the gasses used by Miller and Urey.
The atmosphere used in the Miller-Urey experiments was primarily composed of reducing gasses like methane, ammonia, and high levels of hydrogen. Geochemists now believe that the atmosphere of the early Earth did not contain appreciable amounts of these components. UC Santa Cruz origin-of-life theorist David Deamer explains in the journal Microbiology & Molecular Biology Reviews:
This optimistic picture began to change in the late 1970s, when it became increasingly clear that the early atmosphere was probably volcanic in origin and composition, composed largely of carbon dioxide and nitrogen rather than the mixture of reducing gases assumed by the Miller-Urey model. Carbon dioxide does not support the rich array of synthetic pathways leading to possible monomers...3
Likewise, an article in the journal Science stated: "Miller and Urey relied on a 'reducing' atmosphere, a condition in which molecules are fat with hydrogen atoms. As Miller showed later, he could not make organics in an 'oxidizing' atmosphere."4 The article put it bluntly: "the early atmosphere looked nothing like the Miller-Urey situation."5 Consistent with this, geological studies have not uncovered evidence that a primordial soup once existed.6
There are good reasons why the Earth's early atmosphere did not contain high concentrations of methane, ammonia, or other reducing gasses. The Earth's early atmosphere is thought to have been produced by outgassing from volcanoes, and the composition of those volcanic gasses is related to the chemical properties of the Earth's inner mantle. Geochemical studies have found that the chemical properties of the Earth's mantle would have been the same in the past as they are today.7 But today, volcanic gasses do not contain methane or ammonia, and are not reducing.
A paper in Earth and Planetary Science Letters found that the chemical properties of the Earth's interior have been essentially constant over Earth's history, leading to the conclusion that "Life may have found its origins in other environments or by other mechanisms."8 So strong is the evidence against pre-biotic synthesis of life's building blocks that in 1990 the Space Studies Board of the National Research Council recommended that origin-of-life investigators undertake a "reexamination of biological monomer synthesis under primitive Earthlike environments, as revealed in current models of the early Earth."9
Because of these difficulties, some leading theorists have abandoned the Miller-Urey experiment and the "primordial soup" theory. In 2010, University College London biochemist Nick Lane stated that the primordial soup theory "doesn't hold water" and is "past its expiration date."10 Instead, he proposes that life arose in undersea hydrothermal vents. But both the hydrothermal vent and primordial soup hypotheses face another major problem.
Problem 2: Forming Polymers Requires Dehydration Synthesis
Assume for a moment that there was some way to produce simple organic molecules on the early Earth. Perhaps they did form a "primordial soup," or perhaps these molecules arose near some hydrothermal vent. Either way, origin-of-life theorists must then explain how amino acids or other key organic molecules linked up to form long chains (polymers) like proteins (or RNA).
Chemically speaking, however, the last place you'd want to link amino acids into chains would be a vast water-based environment like the "primordial soup" or underwater near a hydrothermal vent. As the National Academy of Sciences acknowledges, "Two amino acids do not spontaneously join in water. Rather, the opposite reaction is thermodynamically favored."11 In other words, water breaks down protein chains into amino acids (or other constituents), making it very difficult to produce proteins (or other polymers) in the primordial soup.
Problem 3: RNA World Hypothesis Lacks Confirming Evidence
Let's assume, again, that a primordial sea filled with life's building blocks did exist on the early Earth, and somehow it formed proteins and other complex organic molecules. Origin-of-life theorists believe that the next step in the origin of life is that -- entirely by chance -- more and more complex molecules formed until some began to self-replicate. From there, they believe Darwinian natural selection took over, favoring those molecules which were better able to make copies. Eventually, they assume, it became inevitable that these molecules would evolve complex machinery -- like that used in today's genetic code -- to survive and reproduce.
Have modern theorists explained how this crucial bridge from inert nonliving chemicals to self-replicating molecular systems took place? Not at all. In fact, even Stanley Miller readily admitted the difficulty of explaining this in Discover Magazine:
Even Miller throws up his hands at certain aspects of it. The first step, making the monomers, that's easy. We understand it pretty well. But then you have to make the first self-replicating polymers. That's very easy, he says, the sarcasm fairly dripping. Just like it's easy to make money in the stock market -- all you have to do is buy low and sell high. He laughs. Nobody knows how it's done.12
The most prominent hypothesis for the origin of the first life is called the "RNA world." In living cells, genetic information is carried by DNA, and most cellular functions are performed by proteins. However, RNA is capable of both carrying genetic information and catalyzing some biochemical reactions. As a result, some theorists postulate the first life might have used RNA alone to fulfill all these functions.
But there are many problems with this hypothesis.
For one, the first RNA molecules would have to arise by unguided, non-biological chemical processes. But RNA is not known to assemble without the help of a skilled laboratory chemist intelligently guiding the process. New York University chemist Robert Shapiro critiqued the efforts of those who tried to make RNA in the lab, stating: "The flaw is in the logic -- that this experimental control by researchers in a modern laboratory could have been available on the early Earth."13
Second, while RNA has been shown to perform many roles in the cell, there is no evidence that it could perform all the necessary cellular functions currently carried out by proteins.14
Third, the RNA world hypothesis can't explain the origin of genetic information.
RNA world advocates suggest that if the first self-replicating life was based upon RNA, it would have required a molecule between 200 and 300 nucleotides in length.15 However, there are no known chemical or physical laws that dictate the order of those nucleotides.16 To explain the ordering of nucleotides in the first self-replicating RNA molecule, materialists must rely on sheer chance. But the odds of specifying, say, 250 nucleotides in an RNA molecule by chance is about 1 in 10150 -- below the "universal probability bound," a term characterizing events whose occurrence is at least remotely possible within the history of the universe.17 Shapiro puts the problem this way:
The sudden appearance of a large self-copying molecule such as RNA was exceedingly improbable. ... [The probability] is so vanishingly small that its happening even once anywhere in the visible universe would count as a piece of exceptional good luck.18
Fourth -- and most fundamentally -- the RNA world hypothesis can't explain the origin of the genetic code itself. In order to evolve into the DNA/protein-based life that exists today, the RNA world would need to evolve the ability to convert genetic information into proteins. However, this process of transcription and translation requires a large suite of proteins and molecular machines -- which themselves are encoded by genetic information.
All of this poses a chicken-and-egg problem, where essential enzymes and molecular machines are needed to perform the very task that constructs them.
Problem 4: Unguided Chemical Processes Cannot Explain the Origin of the Genetic Code.
To appreciate this problem, consider the origin of the first DVD and DVD player. DVDs are rich in information, but without the machinery of a DVD player to read the disk, process its information, and convert it into a picture and sound, the disk would be useless. But what if the instructions for building the first DVD player were only found encoded on a DVD? You could never play the DVD to learn how to build a DVD player. So how did the first disk and DVD player system arise? The answer is obvious: a goal-directed process -- intelligent design -- is required to produce both the player and the disk.
In living cells, information-carrying molecules (such as DNA or RNA) are like the DVD, and the cellular machinery that reads that information and converts it into proteins is like the DVD player. As in the DVD analogy, genetic information can never be converted into proteins without the proper machinery. Yet in cells, the machines required for processing the genetic information in RNA or DNA are encoded by those same genetic molecules -- they perform and direct the very task that builds them.
This system cannot exist unless both the genetic information and transcription/translation machinery are present at the same time, and unless both speak the same language. Not long after the workings of the genetic code were first uncovered, biologist Frank Salisbury explained the problem in a paper in American Biology Teacher:
It's nice to talk about replicating DNA molecules arising in a soupy sea, but in modern cells this replication requires the presence of suitable enzymes. ... [T]he link between DNA and the enzyme is a highly complex one, involving RNA and an enzyme for its synthesis on a DNA template; ribosomes; enzymes to activate the amino acids; and transfer-RNA molecules. ... How, in the absence of the final enzyme, could selection act upon DNA and all the mechanisms for replicating it? It's as though everything must happen at once: the entire system must come into being as one unit, or it is worthless. There may well be ways out of this dilemma, but I don't see them at the moment.19
The same problem confronts modern RNA world researchers, and it remains unsolved. As two theorists observed in a 2004 article in Cell Biology International:
The nucleotide sequence is also meaningless without a conceptual translative scheme and physical "hardware" capabilities. Ribosomes, tRNAs, aminoacyl tRNA synthetases, and amino acids are all hardware components of the Shannon message "receiver." But the instructions for this machinery is itself coded in DNA and executed by protein "workers" produced by that machinery. Without the machinery and protein workers, the message cannot be received and understood. And without genetic instruction, the machinery cannot be assembled.20
Problem 5: No Workable Model for the Origin of Life
Despite decades of work, origin-of-life theorists are at a loss to explain how this system arose. In 2007, Harvard chemist George Whitesides was given the Priestley Medal, the highest award of the American Chemical Society. During his acceptance speech, he offered this stark analysis, reprinted in the respected journal Chemical and Engineering News:
The Origin of Life. This problem is one of the big ones in science. It begins to place life, and us, in the universe. Most chemists believe, as do I, that life emerged spontaneously from mixtures of molecules in the prebiotic Earth. How? I have no idea.21
Many other authors have made similar comments. Massimo Pigliucci states: "[I]t has to be true that we really don't have a clue how life originated on Earth by natural means."22 Or as science writer Gregg Easterbrook wrote in Wired, "What creates life out of the inanimate compounds that make up living things? No one knows. How were the first organisms assembled? Nature hasn't given us the slightest hint. If anything, the mystery has deepened over time."23
Likewise, the aforementioned article in Cell Biology International concludes: "New approaches to investigating the origin of the genetic code are required. The constraints of historical science are such that the origin of life may never be understood."24 That is, they may never be understood unless scientists are willing to consider goal-directed scientific explanations like intelligent design.
References:
[1.] See Stanley L. Miller, "A Production of Amino Acids under Possible Primitive Earth Conditions," Science, 117: 528-529 (May 15, 1953).
[2.] See Jonathan Wells, Icons of Evolution: Why Much of What We Teach About Evolution Is Wrong, (Washington D.C.: Regnery, 2000); Casey Luskin, "Not Making the Grade: An Evaluation of 19 Recent Biology Textbooks and Their Use of Selected Icons of Evolution," Discovery Institute (September 26, 2011).
[3.] David W. Deamer, "The First Living Systems: a Bioenergetic Perspective," Microbiology & Molecular Biology Reviews, 61:239 (1997).
[4.] Jon Cohen, "Novel Center Seeks to Add Spark to Origins of Life," Science, 270: 1925-1926 (December 22, 1995).
[5.] Ibid.
[6.] Antonio C. Lasaga, H. D. Holland, and Michael J. Dwyer, "Primordial Oil Slick," Science, 174: 53-55 (October 1, 1971).
[7.] Kevin Zahnle, Laura Schaefer, and Bruce Fegley, "Earth's Earliest Atmospheres," Cold Spring Harbor Perspectives in Biology, 2(10): a004895 (October, 2010) ("Geochemical evidence in Earth's oldest igneous rocks indicates that the redox state of the Earth's mantle has not changed over the past 3.8 Gyr"); Dante Canil, "Vanadian in peridotites, mantle redox and tectonic environments: Archean to present," Earth and Planetary Science Letters, 195:75-90 (2002).
[8.] Dante Canil, "Vanadian in peridotites, mantle redox and tectonic environments: Archean to present," Earth and Planetary Science Letters, 195:75-90 (2002) (internal citations removed).
[9.] National Research Council Space Studies Board, The Search for Life's Origins (National Academy Press, 1990).
[10.] Deborah Kelley, "Is It Time To Throw Out 'Primordial Soup' Theory?," NPR (February 7, 2010).
[11.] Committee on the Limits of Organic Life in Planetary Systems, Committee on the Origins and Evolution of Life, National Research Council, The Limits of Organic Life in Planetary Systems, p. 60 (Washington D.C.: National Academy Press, 2007).
[12.] Stanley Miller quoted in Peter Radetsky, "How Did Life Start?" Discover Magazine (Nov., 1992).
[13.] Richard Van Noorden, "RNA world easier to make," Nature News (May 13, 2009).
[14.] See Stephen C. Meyer, Signature in the Cell: DNA and the Evidence for Intelligent Design, p. 304 (New York: HarperOne, 2009).
[15.] Jack W. Szostak, David P. Bartel, and P. Luigi Luisi, "Synthesizing Life," Nature, 409: 387-390 (January 18, 2001).
[16.] Michael Polanyi, "Life's Irreducible Structure," Science, 160 (3834): 1308-1312 (June 21, 1968).
[17.] See William A. Dembski, The Design Inference: Eliminating Chance through Small Probabilities (Cambridge University Press, 1998).
[18.] Robert Shapiro, "A Simpler Origin for Life," Scientific American, pp. 46-53 (June, 2007).
[19.] Frank B. Salisbury, "Doubts about the Modern Synthetic Theory of Evolution," American Biology Teacher, 33: 335-338 (September, 1971).
[20.] J.T. Trevors and D.L. Abel, "Chance and necessity do not explain the origin of life," Cell Biology International, 28: 729-739 (2004).
[21.] George M. Whitesides, "Revolutions In Chemistry: Priestley Medalist George M. Whitesides' Address," Chemical and Engineering News, 85: 12-17 (March 26, 2007).
[22.] Massimo Pigliucci, "Where Do We Come From? A Humbling Look at the Biology of Life's Origin," in Darwin Design and Public Education, eds. John Angus Campbell and Stephen C. Meyer (East Lansing, MI: Michigan State University Press, 2003), p. 196.
[23.] Gregg Easterbrook, "Where did life come from?," Wired, p. 108 (February, 2007).
