Famine, not calcium absorption, may have driven evolution of milk tolerance in Europeans
Posted: 22 Jan 2014 06:18 AM PST
Ancient DNA from early Iberian farmers shows that the wideheld evolutionary hypothesis of calcium absorption was not the only reason Europeans evolved milk tolerance. In the West, people take milk drinking for granted because most people of European decent are able to produce the enzyme lactase in adulthood and so digest the milk sugar lactose. However, this is not the norm in much of the world, and was not the norm for our Stone Age ancestors.
Excerpt: “if natural selection is driving lactase persistence evolution in a place where people have no problems making vitamin D in their skin, then clearly the vitamin D and calcium explanation (known as the calcium assimilation hypothesis) isn’t cutting it. So while the calcium assimilation hypothesis may have some relevance in Northern Europe it’s clearly not the whole story.”
My comment: This evidence refutes mutation-driven evolution via another example of how ecological variation leads to adaptations. It is a refutation of theory that can be compared to the refutation of mutation-driven evolution in the peppered moth. Moth larvae fed lead and manganese-contaminated leaves exhibited the morphological (i.e., color) change. The physiology of moth reproduction is nutrient-dependent and pheromone-controlled. However, a failed replication attempt in the moths led to the ongoing belief in mutation-initiated natural selection in moths and in other species despite no experimental evidence to support it.
That’s why Denis Noble said: If you learnt evolutionary biology and genetics a decade or more ago you need to be aware that those debates have moved on very considerably, as has the experimental and field work on which they are based.
Journal article excerpt: “Others have suggested that a milk–‐rich diet may offer some protection against malaria (Anderson and Vullo 1994; Cordain, et al. 2012).”
My comment: The logic of conserved molecular mechanisms in epigenetically-effected ecological adaptations also refutes the malarial parasite link to mutation-initiated changes in hemoglobin by indicating that the 1181 different forms of hemoglobin are adaptations to ecological variation.
By the end of this year, there will probably be nothing left of any theory that involves mutation-initiated natural selection, and few experimentally unsubstantiated mentions of what once was referred to as mutation-driven evolution. What we will see is reports like this one on ecological variation and adaptations that replace theories with experimental evidence of cause and effect.
