Basics of Evolution: Koonin's calculations (Evolution)

by David Turell , Saturday, January 02, 2016, 18:41 (3029 days ago) @ dhw

dhw: For evolution to take place, it&apos;s the variations that are essential. Otherwise the process will stick at replication.-Of course we are stuck at replication, no matter what the environmental variations!-In Koonin&apos;s famous article for a multiworlds scenario he produced a back of the envelop calculation for the odds of a accurately replicating RNAzyme:- http://www.biologydirect.com/content/2/1/15#sec8-&quot;A ribozyme replicase consisting of ~100 nucleotides is conceivable, so, in principle, spontaneous origin of such an entity in a finite universe consisting of a single O-region cannot be ruled out in this toy model (again, the rate of RNA synthesis considered here is a deliberate, gross over-estimate). -&quot;The requirements for the emergence of a primitive, coupled replication-translation system, which is considered a candidate for the breakthrough stage in this paper, are much greater. At a minimum, spontaneous formation of: -&quot;- two rRNAs with a total size of at least 1000 nucleotides-&quot;- ~10 primitive adaptors of ~30 nucleotides each, in total, ~300 nucleotides-&quot;- at least one RNA encoding a replicase, ~500 nucleotides (low bound)is required. In the above notation, n = 1800, resulting in E <10-1018. -&quot;In other words, even in this toy model that assumes a deliberately inflated rate of RNA production, the probability that a coupled translation-replication emerges by chance in a single O-region is P < 10-1018. Obviously, this version of the breakthrough stage can be considered only in the context of a universe with an infinite (or, in the very least, extremely vast) number of O-regions. -&quot;The model considered here is not supposed to be realistic by any account. It only serves to illustrate the difference in the demands on chance for the origin of different versions of the breakthrough system and hence the connections between these versions and different cosmological models of the universe.-Comment: This is smaller chance than Morowitz 10^40,000 estimate of many years ago. It directly supports my initial response to Romansh&apos;s post. Life MUST start with accurate replication. Varying environmental locations offer a tiny hope to improve chances, but no much at the odds quoted.