September 4, 2007 | David F. Coppedge

Do Genes Reveal the Cambrian Explosion?

A Croatian geneticist believes he can find the Cambrian Explosion in the genes.  Science Daily told about Tomislav Domazet-Loso from the Rudjer Boskovic Institute in Zagreb, whose team employed a “novel methodological approach in evolutionary studies” they called “genomic phylostratigraphy.”  Looking for a “genetic trigger” for the Cambrian explosion, they hoped their method can “shed new and unexpected light on some of the long standing macroevolutionary issues, which have been puzzling evolutionary biologists since Darwin.
    Acknowledging that fossils provide the only direct evidence of what happened, they proposed a “novel and interesting approach” to get around the patchy fossil record:

Namely, they suggested that the genome of every extant species carries the ‘snapshots’ of evolutionary epochs that species went trough [sic].  What’s even more important, they also developed the method which enables evolution researchers to readily convert those individual ‘snapshots’ into the full-length ‘evolutionary movie’ of a species.
    Applying their new methodology on the fruit fly genomic data they tackled some of the most intriguing evolutionary puzzles – some of which distressed even Darwin himself.  First, they demonstrated that parts of the living organism exposed to the environment – so called ‘ectoderm’ – are more prone to evolutionary changes.  Further, they explained the evolutionary origin of the ‘germ layers’, the primary tissue forms that form during the first days after the conception of a new animal, and from which subsequently all other tissues are developed.  Finally, they discovered the potential genetic trigger for the ‘Cambrian explosion’, a major global evolutionary event on the planet, when some 540 million years ago almost all animal forms known today suddenly ‘appeared’.

The details of their method were to be presented at a conference in Croatia Sept. 4-5 and published in the November issue of Trends in Genetics.  It is not clear how the RBI team would explain the mystery of ultraconserved elements (see 08/18/2007 entry and press release from Berkeley Lab).  Scientists found numerous long sequences that were identical in mice and humans, yet appeared to have no effect on mice when deleted.  “The 731-base pair sequence, uc467, should normally have accumulated some 334 nucleotide changes in the more than 80 million years that mice, rats, and humans have been evolving along separate paths,” the press release stated.  This seems to contradict the assumption of the Croatian team that each species contains a genetic movie of its evolutionary history.  The Berkeley team called their findings a “major challenge to our understanding of how highly conserved elements of the genome persist.”  That’s because “evolutionary pressures” should have forced only functional elements to be conserved, while others would have accumulated mutations over millions of years.

So poor old Charlie was distressed.  All the major body plans appeared suddenly without the missing links his theory demanded.  No wonder.  The fossil record, the only direct line of evidence available, looked like creation.  (For details on the Cambrian explosion and evolutionary proposals to explain it, see the 04/23/2006 entry).
    This new idea does nothing to explain how new body plans suddenly “appeared” (how’s that for another Darwinian miracle word).  It is nothing but recapitulation theory resurrected in a new form.  Coining a tongue-twisting euphemism like genetic phylostratigraphy doesn’t make a dumb idea smarter.  For Haeckel, each embryo supposedly recapitulated its evolutionary history.  Haeckel proceeded to impose his vision onto uncooperative data, and then he saw what his faith required.  Now, for Domazet-Loso, each genome recapitulates its evolutionary history.  If he hadn’ta believed it, he wouldn’ta seen it.

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Categories: Fossils, Genetics

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