One of the things that really pisses me off about the Evolution-Creation “debate” is that it uses up oxygen that could be profitably allotted to documenting the tsunami of data emerging out of the “post-genomic” era. The actual examination of evolution is not just an academic exercise, as much of the recent work coming out of laboratories deals with humans.1 For example, Dienekes points me to this preprint in The American Journal of Human Genetics, Spread of an inactive form of caspase-12 in humans due to recent positive selection:
…There is strong evidence for positive selection from low diversity, skewed allele frequency spectra and the predominance of a single haplotype. We suggest that the inactive form of the gene arose in Africa ~100-500 thousand years ago (KYA) and was initially neutral or almost neutral, but that positive selection beginning ~60-100 KYA drove it to near-fixation. We further propose that its selective advantage was sepsis resistance in populations that experienced more infectious diseases as population sizes and densities increased.
Dienekes provides a map that shows the distribution of the alleles:
In other news, Dienekes again points me to something I’ve been keeping track of, the argument by Alan Templeton that Out-of-Africa is rejected by multiple loci analysis. That is, Out-of-Africa is predicated in large part (though not exclusively) on uniparentally inherited neutral markers, mtDNA and nonrecombinant Y. Leaving aside whether these are neutral (some lineages of mtDNA might actually be more fit than others for a variety of reasons), other loci can give different results, which is what Templeton uses as the linchpin for his hypothesis. This post by Carl Zimmer has an image which graphically illustrates Templeton’s model. Basically it shows a trellis, where alleles shift between populations and ancestry is reticulated between different homonid lineages.
This breaks out of the old Multiregionalism vs. Out-of-Africa dichotomy, it is not simple and evades a general solution to questions of modern human origins (I suspect that the balance of evidence will point to mostly African ancestry, with a residue of advantageous alleles from other lineages, some worldwide in distribution and some localized).2 Templeton’s model is not the only one out there that attempts to draw on the wealth of information that genomics offers in reconstructing gene phylogenies and inferring from that to population phylogeny (he probably uses too few loci according to an acquaintance of mine). It is often stated that the homonid family tree is a bush, if these models pan out the origin of modern humans may resemble brambles and knots far more than the current consensus.
1 – Humans are a very important “model organism,” as studying human genetics allows you to make a good argument to the NIH as well as the NSF when it comes to getting grant money.