Agriculture, dietary changes, and adaptations in fat metabolism from ancient to modern Europeans

Good vs bad cholesterol. Margarine vs butter. Red meat vs. vegan. The causal links between fats and health have been a hotly debated topic for scientists, physicians and the public.
Now, evolutionary biologists are weighing in based on the increasing power of DNA analyses to explore how changes in diet over eons have caused human adaptations to genes regulating fat metabolism.
Nestled on the long arm of chromosome 11, two essential genes serve as key traffic police in the synthesis of vital fatty acids. These genes, called fatty acid desaturase 1 and 2 (FADS1 and 2), change dietary fat into components necessary for the heart, brain and muscle. They assist in the conversion of short-chain omega-3 and omega-6 poly-unsaturated fatty acids (PUFAs) to long-chain PUFAs.
Scientists have recently shown that FADS genes are frequent targets of natural selection in humans. Before modern humans moved out of Africa, roughly 85,000 years ago, natural selection targeted variants in these genes presumably associated with changes in diet. After people moved out of Africa and encountered new environments, selection again targeted the FADS genes for humans to better adapt to local conditions. Previous studies have argued that the Inuit in Greenland have adapted to a diet rich in fatty acid from animal sources, and that some groups in India have adapted to a more vegetarian diet , through changes in the DNA in the FADS genes.
"The FADS genes seem to have been frequent targets of natural selection throughout human history as our diet has been changing as a consequence of new hunting or agricultural practices", says Rasmus Nielsen, a professor of Integrative Biology at UC Berkeley, and co-author of a new study on selection on FADS genes in Europe.
In the new study, Nielsen and his colleagues examine data from 101 Bronze Age individuals and present-day human data from the 1000 Genomes Project. Nielsen's research team analyzed adaptive mutations in the FADS region in Europeans, to determine which mutations might have been targeted by recent natural selection in Europeans and to investigate the physiological effects of the mutations.
They found that certain single DNA mutations (SNPs) have been targeted by selection in Europeans since the Bronze Age, and likely before that as well, to increase the production of the long-chain PUFAs: arachidonic and eicosapentaenoic acid. This pattern mirrors the one observed in some Indian populations but is exactly opposite of that observed in the Greenlandic Inuit. Individuals on a more vegetarian diet ingest more short-chain PUFAs, while individuals having a high intake of animal fat ingest more long-chain PUFAs. The need for additional production of these PUFAs, therefore, depends on the dietary intake. As Inuit switched to a diet based on marine mammals, they would need to produce fewer long-chain PUFAs, but when people in India switched to a more vegetarian diet they would need to increase the production.