John Hawks continues to post interesting articles on his blog and he continues his policy of not allowing comments. I want to ask a question about his latest posting [A horse of a different color] so I'm asking it here.
John is referring to a short paper on the evolution of coat colors in horses. Apparently, the analysis of DNA from ancient fossil horses reveals that most of them were bay in color. The chestnut coat color wasn't detected until about nine thousand years ago.
The authors of the paper claim there is no evidence for selection of coat color in horses prompting the following comment by John Hawks.
The pigment-altering mutations at these genes do not all show statistical signs of selection in contemporary samples of horses. But they aren't there in the ancient horses. That's the best evidence of selection you could possibly have. Message: tests of selection on contemporary samples are weak, particularly for loci with rare alleles or more than two alleles.John, if I understand you correctly, you're saying that as long as an allele wasn't detectable in ancient populations but is detectable today then random genetic drift is ruled out.
That doesn't make sense to me. Perhaps you could explain? There must be more to your statement than that.