There’s a new article out in ASHG that discusses a regional selective sweep in CPT1A, carnitine palmitoyltransferase 1A, which plays an essential role in fatty acid metabolism. A mutation has become extremely common, with a gene frequency > 50%, in northeast Siberian populations, Eskimos, and Aleuts. This happened even though the c.1436C>T mutation has some negative side effects, such as reduced fasting tolerance and, apparently, a higher risk of infant death.

It looks as if this variant conferred significantly higher fitness (~15%) over the past few thousand years and has increased very rapidly. Almost certainly, this has something to do with traditional diets in these areas, in which fat provided 80-85% of energy and protein 15-20%, with hardly any carbohydrates. We’ll know more about the biochemical details of how this mutation works when someone makes a mouse model.

This could only happen in the Arctic, where agriculture is impossible, plant foods limited, and marine mammals use blubber as insulation.

It illustrates an important point, mentioned in our book: an ancestral diet might have some payoff, but likely the appropriate diet would be the foods eaten by your ancestors, not somebody else’s.