My initial comment on an article was not posted to the site, which sometimes happens due to attempts to limit comments that move further forward than what the journalist could do. Besides, in this case, the journalist does not make himself clear. The questions remain: 1) What is selected? 2) How is that selected? The journalist finds selection (e.g., again) and then appears to lose it in the context of theory. That’s probably best, since he ventures into dangerous territory with this comment: “…there seems to be less evidence for positive selection in Sub-Saharan Africans…”
See for example: Peeling back the palimpsest, and finding selection again
“…does evolution result in an infinitely creative assortment due to chance events, or does it drive toward a finite set of idealized forms which populate the possible parameter space?*”
My comment: That’s a confusing question, but it can be answered with current evidence of epigenetic cause and effect sans mutations theory. Isn’t population of the “possible parameter space” the same as ecological niche construction? I suggest comparison to companion reports from Harvard that detail adaptive evolution of a human population during the past ~30.000 years due to a single amino acid substitution as reported earlier this year in Kamberov et al, and in Grossman et al. There’s lots to see in those reports, if you are willing to look beyond mutation-driven evolution and consider nutrient-dependent pheromone-controlled adaptive evolution. For example, the conserved molecular mechanisms of the olfactory and immune systems in the context of self / non-self identification of food or conspecifics might be an important feature of adaptive evolution across species.
If my comment had been posted before its second submission, I might also have addressed the published work from Petrov’s group, which recently got lots of attention for their approach to balancing selection. See Strong Purifying Selection at Synonymous Sites in D. melanogaster. Until now, it appears that no one thought to compare deleterious synonymous mutations to base pair changes associated with the nutrient-dependent microRNA/messenger RNA balance. That “balanced” selection incorporates single amino acid substitutions that link non-synonymous SNPs to nutrient-dependent protein biosynthesis. The metabolism of the nutrients (e.g., protein degradation) is also linked to species-specific pheromones that control reproduction in species from microbes to man.
Perhaps there are still too many people who think in terms of mutation-driven evolution, despite the fact that synonymous mutations are deleterious. If all you consider is the deleterious synonymous mutations, you’re not likely to find evidence for positive selection that begins with the selection of nutrients that metabolize to pheromones that control reproduction. Thus, the failure to consider biological facts about controlled reproduction may have led to errant theories that include mutation-driven evolution, when there is no evidence for it in any species.
Finding Darwinian selection again is merely a matter of approaching it from Darwin’s perspective on ‘conditions of life’ that are nutrient-dependent and pheromone-controlled. Selection is for nutrients in all species, and reproduction is controlled by pheromones, which includes sexual reproduction in species that metabolize nutrients to sexually dimorphic pheromones that control sexual reproduction. Razib Khan might be commended for suggesting “…the demographic pulse across Eurasia, and to the New World and Australasia, naturally resulted in local adaptations as environmental conditions shifted.” Minimally, the demographic pulse can be linked to control of the gonadotropin releasing hormone (GnRH) pulse by nutrient uptake (e.g., glucose) and by the metabolism of nutrients to species-specific pheromones in my model, which links the epigenetic effects of olfactory/pheromonal input in species from microbes to man. Instead, Khan will probably be denigrated for his comment about “…less evidence for positive selection in Sub-Saharan Africans…” Comments like that tend to force others to react and lose selection again, because positive selection must always occur for adaptive evolution to occur.