As new techniques arise in sequence analysis, as well as in genetic engineering, new frontiers open up to test the direction and power of natural selection. A new such experiment has been performed by a team including Joe Thornton.
Here’s the opening sentences from the paper:
We generated a large alignment of ADH sequences, determined the best-fit evolutionary model, inferred the maximum likelihood phylogeny and calculated the posterior probability distribution of amino acid states at key ancestral nodes. We synthesized coding
sequences for the maximum a posteriori sequence of AncMS, which was inferred with high confidence and only one ambiguously reconstructed amino acid (Fig. 1b, Supplementary Fig. 1), and for an alternative version of AncMS (Alt-AncMS), which contained the other plausible state at the ambiguous site and was identical to D.simulans ADH. We also characterized the inferred ancestral D.melanogaster ADH, the amino acid sequence of which is identical to that of the ‘slow’ allele present in extant populations, which is known to be older than other ADH variants.”
At Phys.Org, here’s what the PR has to say:
Thornton and Siddiq reasoned that by combining ancestral gene reconstruction with techniques for engineering transgenic animals, they could study how genetic changes that occurred in the deep past affected whole organisms-their development, physiology, and even their fitness.
“This strategy of engineering ‘ancestralized animals’ could be applied to many evolutionary questions,” Thornton said. “For the first test case, we chose a classic example of adaptation-how fruit flies evolved the ability to survive the high alcohol concentrations found in rotting fruit. We found that the accepted wisdom about the molecular causes of the flies’ evolution is simply wrong.“
Did I hear that correctly? The “accepted wisdom about the molecular causes of the fly’s evolution is SIMPLY WRONG?
Yes, that’s right. Because later on in the PR we read:
Siddiq and Thornton realized that this hypothesis could be tested directly using the new technologies. Siddiq first inferred the sequences of ancient Adh genes from just before and just after D. melanogaster evolved its ethanol tolerance, some two to four million years ago. He synthesized these genes biochemically, expressed them, and used biochemical methods to measure their ability to break down alcohol in a test tube. The results were surprising: the genetic changes that occurred during the evolution of D. melanogaster had no detectable effect on the protein’s function.
What’s that you say? No detectable effect?
One supposes that the gene selected is one, among very many, that can be best ‘reverse-engineered’ to give a facsimile of the ‘ancient’ form. Yet, when tested in vivo, there is no difference found between the supposed ‘slow’ ancestral gene, and the ‘fast’ extant form. This is not how neo-Darwinism is supposed to work. Something is seriously wrong, no?
It might be that the techniques employed to identify the ‘ancestral’ form are bad. Maybe that’s it, and it alone. But, OTOH, maybe something is seriously wrong with current neo-Darwinian theory.
From the very end of the “Discussion” section:
Some notions concerning adaptation will
therefore remain difficult to study rigorously. Nevertheless, because
of technical and conceptual advances, it should now be possible to
experimentally assess the causal predictions of many previously
untested or weakly tested hypotheses of historical molecular adaptation,
allowing them to be corroborated or, like the classic hypothesis
of ADH divergence in D.melanogaster, decisively refuted.
One wonders what’s really left of Darwinism. Between Behe’s Edge of Evolution, Shapiro’s “Natural Genetic Engineering,” the whole field of epigenetics, the disappearing of “Junk-DNA”, and now the disappearance of a ‘fitness’ change in a “classic case” of molecular adaptation, can anyone seriously believe that Darwinism has much to say about how life evolves?
This is the Phys.Org Press Release.