Sudden Evolutionary Change 2,500 B.C.

Ok, being a little facetious.  Anyhow, whatever the mechanism, stuff changes in Bronze Age Northern Europe.
drip, drip...

Selection in Europeans on fatty acid desaturases associated with dietary changes

Matthew T. Buckley, Fernando Racimo, Morten E. Allentoft, Majken K. Jensen, Anna Jonsson, Hongyan Huang, Farhad Hormozdiari, Martin Sikora, Davide Marnetto, Eleazar Eskin...More
Mol Biol Evol msx103.   DOI:  https://doi.org/10.1093/molbev/msx103

Published:
16 March 2017

Abstract: FADS genes encode fatty acid desaturases that are important for the conversion of short chain polyunsaturated fatty acids (PUFAs) to long chain fatty acids. Prior studies indicate that the FADS genes have been subjected to strong positive selection in Africa, South Asia, Greenland, and Europe. By comparing FADS sequencing data from present-day and Bronze Age (5-3k years ago) Europeans, we identify possible targets of selection in the European population, which suggest that selection has targeted different alleles in the FADS genes in Europe than it has in South Asia or Greenland. The
alleles showing the strongest changes in allele frequency since the Bronze Age show associations with expression changes and multiple lipid-related phenotypes. Furthermore, the selected alleles are associated with a decrease in linoleic acid and an increase in arachidonic and eicosapentaenoic acids among Europeans; this is an opposite effect of that observed for selected alleles in Inuit from Greenland.  We show that multiple SNPs in the region affect expression levels and PUFA synthesis. Additionally, we find evidence for a gene-environment interaction influencing low-density lipoprotein (LDL) levels between alleles affecting PUFA synthesis and PUFA dietary intake: carriers of the derived allele display lower LDL cholesterol levels with a higher intake of PUFAs. We hypothesize that the selective patterns observed in Europeans were driven by a change in dietary composition of fatty acids following the transition to agriculture, resulting in a lower intake of arachidonic acid and eicosapentaenoic acid, but a higher intake of linoleic acid and α-linolenic acid.