The study, published in Molecular Biology and Evolution, was conducted by scientists at the University of California, Berkley, and led by Professor Rasmus Nielsen. Made possible by recent advances in ancient genome sequencing, the team had access to hundreds of genome sequences from humans today, and sequences from 101 people who resided in Europe 5,000 years ago during the Bronze Age.
MBE latest: Selection in Europeans on fatty acid desaturases associated with dietary changes https://t.co/bcfea7lN5x— OfficialSMBE (@OfficialSMBE) March 20, 2017
By comparing the two, they found two particular regions of DNA underwent intense selection over the past several thousand years and changed rapidly in response to evolutionary pressures.
These regions contain two genes — called "fatty acid desaturase 1 and 2," or FADS1 and 2 for short — which regulate how the human body converts short-chain poly-unsaturated fatty acids (PUFAs) into long-chain PUFAs for the health of tissues such as muscles and the brain.
The findings indicate the FADS genes of Bronze Age Europeans experienced significant mutations over the millennia, to produce more long-chain PUFAs.
Nielsen et al believe the European variant of FADS genes are likely the result of agricultural lifestyles, leading to diets rich in wheat and vegetables. When humans in Europe and the Middle East began to practice farming over 10,000 years ago, suddenly they were ingesting far more short-chain PUFAs. People who could convert short-chain PUFAs into long-chain PUFAs efficiently were more likely to survive, so their FADS genes were passed on to succeeding generations.
Likewise, favorable FADS variants also helped humans adapt to a vegetarian-based diet in India.
"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. [They have] changed in multiple ways in different parts of the world. Generally, we see selection favoring alleles associated with a diet rich in animal fat outside Africa, more so than inside Africa. Possibly, as modern humans move outside Africa, they encountered new opportunities for hunting large mammals," said Professor Bielsen.
FADS genes are still changing — given European diets are far higher in sugar and fat in the 21st century (with obviously escalating ramifications for caloric intake), their selection is unlikely to be functioning in the same manner it did 5,000 years ago. The study suggests this may indicate the FADs of "paleo dieting" — a diet centered on meat, vegetables and grains, predicated on the assumption human nutritional needs haven't changed since the era of hunter-gatherers — is based on erroneous foundations.
The team also looked for FADS variants in 40,000 year-old Neanderthal and Denisovan genes, and found they appear to have been a target for natural selection in these ancient humans as well. This suggests FADS variants could predate the divergence of modern humans and Neanderthals, over 400,000 years ago — or modern humans and Neanderthals both inherited these genetic variants by interbreeding with some other hominid.
The team also analyzed 483 genomes from 148 populations populations the world over, and concluded all humans living today can trace their ancestry back to a single group that emerged in Africa 200,000 years ago — with all non-Africans descended from a single group split from the ancestors of African hunter gatherers around 130,000 years ago.