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The Koonin threshold for the Origin of Life on Earth
A 'review' of The Logic of Chance
In Chapter 12 Koonin discusses the origin of life, that is: the emergence of translation, replication, metabolism and membranes. Life as it is today is a DNA-protein world. However, the DNA-protein world is a non-starter. The DNA-protein world faces the proverbial chicken-and-egg problem: what comes first, DNA or protein? DNA is needed to produced proteins and DNA needs proteins to get replicated, transcribed and translated into proteins. To solve this chicken-and-egg problem, the RNA-world is logical inevitable. RNA can function both as protein (enzyme) and replicator. However, even under the best-case scenario, the RNA-World hardly has the potential to evolve beyond very simple "organisms" (p. 366). The path from a putative RNA World to a translation system (DNA-protein world) is incredibly steep (p. 376). The hardest problem is that evolution by natural selection can only start after replication with sufficient fidelity is established (2). Not withstanding all scientific progress, we currently do not have a credible solution to these problems (4).
Why is it so difficult to evolve a DNA-protein world from a RNA-world? Here is Koonin's specification of the requirements of a coupled replication-translation system (p. 435) (these calculations are the same as in: 3 ):
The probability of the spontaneous origin of this is: P < 10-1018. The spontaneous origin of 1,800 nucleotides is the Koonin-threshold for the origin of life and evolution. No Origin of Life (OOL) researcher put it more clearly and dramatically than Koonin. Please note 1,800 nucleotides is a minimum. Every OOL researcher that skips over the Koonin threshold makes a serious scientific oversight. Here are two graphical representations of the Koonin threshold.
Figure 12-6 shows that at most ribozymes could spontaneously originate, but not a coupled replication-translation system (the DNA-protein world). So, if ribozymes are the beginnings of the RNA-world, Koonin claims that the RNA-world would come to a halt before a replication-translation system emerged. In our universe, certainly on our earth (5), the RNA-world would be a dead end.
In figure 12-7B the threshold of biological evolution would equal 1,800 nucleotides. Despite this, life exists on this earth. Now, Koonin invokes a radical alternative: Eternal Inflation Cosmology. The Many Worlds in One (MWO) changes the very definition of what is possible, likely, and random in such a way that the probability of the realization of any scenario in an infinite multiverse is exactly 1.
"Thus, spontaneous emergence of complex systems that would have to be considered virtually impossible in a finite universe becomes not only possible, but inevitable under MWO." (p. 385).This is the most unorthodox, subversive claim in the whole 516 page book. This radical change in thinking must have happened 2007 May 31 when Koonin published an 'optimistic' mainstream publication with Yuri Wolf (2) and a 'pessimistic' publication (3) without coauthor. The second publication has been reviewed by four researchers. One reviewer (Eric Bapteste) was afraid that Koonin's views "could open a huge door to the tenants of intelligent design". Koonin replied that "Properly interpreted, the anthropic principle is a death knell to ID" and that biologists should not stop publishing research on hard problems in evolutionary biology and should not declare these hard problems solved. The ID crowd will interpret these results as support for their cause anyway." I fully agree with Koonin. David Krakauer warns for the danger of invoking the infinite multi-verse: "as well assert that all observed biological order emerged in one step, including the complete evolutionary history of life." According to the fourth reviewer (Itai Yanai) the present model represents the first one to account for the origin of life by explicitly invoking the anthropic principle. The anthropic principle means that only universes in which the transition to Darwinian evolution happened evolved observers. The other universes do not contain (complex) life and thus no observers.
What should we think of this extraordinary scenario? Koonin claims it is falsifiable. According to Koonin his hypothesis can be falsified by the demonstration that the RNA-world can produce a translation system. But if he holds that is a serious possibility, his extravagant proposal cannot be taken very seriously. He could as well have said "We don't know" and hope for a future solution. It is true that nobody before gave such a detailed calculation of a threshold for biological evolution. However, he should have given more details and background information of the calculation of 1,800 nucleotides threshold and not relegated it to the Appendix. It should have been included in chapter 12. For, extraordinary claims should be build on very well researched evidence.
Finally, why not do an experiment? If only 13 RNA molecules with a total length of 1,800 nucleotides are necessary, it should not be that difficult to synthesize them and bring in the right chemical environment and observe the origin of life. If sequences are not (precisely) known, why not start with random sequences? That could verify or falsify Koonin's theory.
Further Reading (Dutch)
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|Copyright ©G. Korthof||First published: 3 Jan 2013||Updated: 3 Jan 2013 F.R./N: 21 Dec 2013|