LiveScience reported on a new “breakthrough” in origin-of-life (OOL) research. Robert Roy Britt began the article by describing the current state of OOL research: “One of life’s greatest mysteries is how it began. Scientists have pinned it down to roughly this: Some chemical reactions occurred about 4 billion years ago – perhaps in a primordial tidal soup or maybe with help of volcanoes or possibly at the bottom of the sea or between the mica sheets – to create biology.”
I like how Britt “pinned it down” to chemical reactions in a soup, or maybe volcanoes, or maybe the sea, or maybe between mica sheets. The specificity is overwhelming. Can you imagine if homicide detectives worked like this?: “Captain, we haven’t caught the killer yet, but we’ve pinned it down to a human being, living on some continent, on this planet.” Good work guys. I’m glad you narrowed it down for us. Now I can check outer-space off my list as a possible location for the origin of life. Oh wait, some scientists think life did originate in outer-space! Maybe the killer isn’t living on this planet after all. Someone better alert the detectives to broaden their search. End of sarcasm.
So what was the big breakthrough?: a self-replicating RNA molecule. Some background information will be helpful. One theory of how life originated from inorganic material by purely chance, natural processes is the RNA-world hypothesis. According to this hypothesis, RNA strands formed from nucleotides, which later gave rise to DNA, proteins, and the basic cell. Among its many problems, however, is the fact that no RNA strand has ever self-replicated in the lab. But Gerald Joyce and his team at the Scripps Research Institute was able to get RNA to do just that. This isn’t much of a breakthrough, however, at least not as it concerns OOL research.
Joyce was able to get RNA to replicate only by engineering the RNA molecules to copy “word-by-word” rather than letter-by-letter (nucleotide by nucleotide). But that is not how RNA replicates in natural conditions, so why think this experiment tells us anything about how RNA might have been able to self-replicate on the early Earth, and how life got started? If anything, it seems to demonstrate that for RNA to replicate apart from the cell requires an intelligent agent to manipulate it into behaving in ways it does not behave in nature. And if that’s what we’re doing, then the results of the experiment don’t tell us anything about the chance, physical process by which life emerged.
Then there is the matter of the nucleotide strings Joyce and his team put in the beaker with the RNA. These raw materials are necessary for RNA replication, but why think they would have been available in the early Earth, and/or available in the quantities and locations needed? If an ancient RNA molecule needed thousands of nucleotides at location X for replication to occur, but only 50 were present at location Y, there would be no replication. As Stuart Kauffman wrote:
The rate of chemical reactions depends on how rapidly the reacting molecular species encounter one another-and that depends on how high their concentrations are. If the concentration of each is low, the chance that they will collide is very much lower. In a dilute prebiotic soup, reactions would be very slow indeed. A wonderful cartoon I recently saw captures this. It was entitled ‘The Origin of Life.’ Dateline 3.874 billion years ago. Two amino acids drift close together at the base of a bleak rocky cliff; three seconds later, the two amino acids drift apart. About 4.12 million years later, two amino acids drift close to each other at the base of a primeval cliff…. Well Rome wasn’t built in a day.[1]
Is it any surprise that if you provide the right kind of “RNA food” in the right quantities, in the right location, and re-program the RNA so that it is able to join itself to those nucleotides, that it does so? No. Because it is not surprising that when an intelligent agent involves itself in the process, what is naturally impossible becomes possible. Take away that intelligent agent, however, and you are left with the impossible. Joyce’s work was not a breakthrough for OOL research, but a reaffirmation of what we already know: intelligent agents can do things nature cannot do on its own.
[1]Stuart Kauffman, At Home in the Universe: The Search for Laws of Self-Organization and Complexity, [1995] (Penguin: London, 1996, reprint), 34-35.
Thinking to Believe 
January 16, 2009 at 11:26 am
I submitted a comment on the Science article, asking how this experiment tells us anything about the OOL since it required intelligent agents to manipulate RNA to act in ways it would never act in nature. I never expected to get a response from Gerald Joyce himself, but he responded:
“Yes, this a “word-by-word” copying, but some have suggested (e.g. James & Ellington, Origins Life Evol. Biosph. 29, 375-390, 1999) that the earliest replicators on Earth were oligo ligators, rather than polymerases. However,
the “words” (oligos) in our experiments are too long to be prebiotically plausible.”
There you have it. The researcher himself admits that his experiment, while interesting, doesn’t get us any closer to providing a plausible naturalistic pathway for the OOL.
Jason
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January 16, 2009 at 11:27 am
I forgot to include the link: http://blogs.sciencemag.org/origins/2009/01/rna-begets-rna.html
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January 18, 2009 at 10:49 am
I disagree. As the article notes, it’s a huge step forward. You can dismiss each step as failing to complete the journey, but after enough steps the journey will eventually be complete. This experiment doesn’t prove everything, but then it doesn’t need to. “A brick is not a wall.”
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January 19, 2009 at 4:59 pm
Arthur,
Yes, Andy Ellington thought it was significant. And I’m not denying that it is. It’s the first time anyone has accomplished this feat. But it’s not a significant breakthrough for a naturalistic understanding of the OOL (which is what it is being spun as by the media). Even Ellington said as much: “Although the work almost certainly doesn’t reflect what happened at the start of life….” More importantly, that’s what Joyce himself notes when he said the engineered RNA was not “prebiotically plausible.” If the goal is to find a naturalistic means of the OOL, and if “RNA-first” is one plausible pathway, and if that pathway requires a self-replicating RNA, and if this experiment does not show that/how RNA can self-replicate in realistic, natural conditions, then this experiment does next-to-nothing to contribute to the RNA-World hypothesis, and a naturalistic understanding of the OOL.
I agree with the principle that a brick need not be a wall to be useful. But when it comes to the RNA-World hypothesis, the way we get one brick excludes us being able to obtain another brick needed to build the wall. For example, RNA needs ribose to form. What forms ribose? DNA. Without DNA, there won’t be much ribose. Other chemical reactions can produce ribose in very small quantities, but they do so in both L- and R-handed varieties. The problem is that only R-handed varieties are useful, and L-handed varieties interfere with RNA synthesis.
Then there is the problem that UV radiation breaks down RNA. It is protected from UV radiation by water, but ribose is unstable in water. It’s hard to form RNA in a warm little pond if there’s no stable ribose in that pond, or stable L-handed varieties mixed along with stable R-handed varieties.
Then there’s also the problem of forming cytosine (without which there is no RNA). While scientists have been able to create it in the lab, it instantly transformed into uracil. And there is no trace of cytosine anywhere in nature outside the cell, so there is no reason to think it was ever available. Furthermore, cytosine and uracil cannot form without phosphorus (a crucial ingredient to RNA), but at best there would have only been trace amounts available. It doesn’t do much good to investigate how RNA might have undergone self-replication in the early Earth if it is chemically impossible for all of the necessary ingredients to form at the same time/place under the same conditions.
Jason
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January 31, 2009 at 9:34 am
Jason,
Have you read this article on ID at TNR?
http://www.tnr.com/politics/story.html?id=1e3851a3-bdf7-438a-ac2a-a5e381a70472
Arthur
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January 31, 2009 at 9:35 am
Jason,
Have you read this article?
http://www.tnr.com/politics/story.html?id=1e3851a3-bdf7-438a-ac2a-a5e381a70472
Arthur
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February 2, 2009 at 11:51 am
I haven’t read it, and by the looks of the length and my current work-load, I probably won’t be doing so any time soon. Michael Egnor of the Discovery Institute plans to review the article at length. His first installment is at http://www.evolutionnews.org/2009/01/reviewing_jerry_coyne.html.
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