Tuesday, January 15, 2008

Location: genes & culture   posted by Razib @ 1/15/2008 05:59:00 PM

p-ter's post about a new allele for lactase persistence is a powerful testament to the reality of gene-culture coevolution. These alleles which allow for lactase persistence have almost certainly spread over the last 10,000 years, and likely within the last 5,000. The fact that multiple alleles arose which exhibit disparate geographic distributions suggests that population substructure was generated in part by physical barriers (e.g., the mountainous massif at the center of Eurasia) which prevented selection from sweeping from deme to deme. This brings me to a note which I think is important to make: the same parameters which make a region amenable to a flow of information (culture) likely results in it being subject to repeated influxes of advantageous alleles from without. In other words, the rich get richer. Along trade routes come both cultural and genetic innovations. We've been discussing recent adaptive evolution and its likely acceleration toward the present, but if you read history you'll also note that cultural change has also sped up a great deal. The society of ancient Egypt spanned over 2,000 years; obviously it was not static, but a farmer during the Old Kingdom would not have been particularly shocked by the customs & norms of the New Kingdom. In contrast, someone from 200 years in the past would be an alien among us.