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← We Are Viral From the Beginning

stuart chelmsford's Avatar Jump to comment 12 by stuart chelmsford

Endogenous retroviruses also provide unequivocal genetic evidence of common ancestry and I am a little surprised that greater reference to them has not been made in recent books on evolution. ERVs essentially insert more or less randomly within the genomes of host organisms and yet we find the same ERV sequences inserted in the very same genomic loci in related organisms. It is probabilistically untenable that so may ERVs could have inserted in the same loci in different species by chance, leaving inheritance down a common germ-line as the only plausible explanation for their presence. The 3' and 5' long terminal repeats on either end of the viral sequences are identical when the virus inserts so the degree of accumulated mutational contrast between the two LTRs also serves as a molecular clock from which the relative age of insertions can be calculated. Furthermore, these orthologous ERV sequences are found in nested hierarchies - more closely related organism possess a greater number of shared sequences inserted more recently at the same points in their genomes, with greater commonality in point mutations on the long terminal repeats on either end of the viral sequence. Together these pieces of evidence can be used to establish very accurate phylogenetic trees. I suggest reading 'Constructing primate phylogenies from ancient retrovirus sequences' (Johnson and Coffin) for an example.

I have found this evidence invaluable when debating hardcore creationists as they simply have no coherent answer to it. The viral origin of the sequences rules out common design arguments, the mechanism of insertion is well documented (as with the KoRV virus) and the nested hierarchies have no credible explanation except common descent. 'Virolution' by Frank Ryan is another interesting read on this subject.

Sun, 17 Jun 2012 11:14:41 UTC | #947744