Multiple Advantageous Amino Acid Variants in the NAT2 Gene in Human Populations:

Data on the structure of haplotypes and their frequencies are compatible with a model in which slow-causing variants were present in widely dispersed populations before major shifts to pastoralism and/or agriculture. In this model, slow-causing mutations gained a selective advantage in populations shifting from hunting-gathering to pastoralism/agriculture. We suggest the diminished dietary availability of folates resulting from the nutritional shift, as the possible cause of the fitness increase associated to haplotypes carrying mutations that reduce enzymatic activity.

Shorter version: a bunch of loss of function mutations which effect enzymatic activity in the ancestral genetic background shot up in frequency across disparate populations with the Neolithic revolution due to dietary changes. The paper is kind of a hodge-podge (e.g., not statistically significant, so let's hand wave :-). Also the appeal to balancing selection generally makes me suspicious...exactly how much balancing selection was their in our species? If there's a lot of it I assume it has more to do with frequency dependence and environmental heterogeneity than heterozygote advantage. Nevertheless, perhaps this is going to go down with amylase and lactase persistence as a recent adaptation driven by the shock of agriculture. I'm certainly not averse to the idea that nutritional deficiences due to the switch to agriculture drove a lot of recent human evolution.

H/T Dienekes

Labels: Genetics, Human Evolution