There’s another report out on selection in the Greenland Inuit. They found clear signs of positive selection in FADS, the fatty acid desaturase gene cluster. More interesting was the discovery of strong selection on a region containing WARS2 and TBX15, located on chromosome 1. WARS2 encodes the mitochondrial tryptophanyl-tRNA synthetase, and TBX15 is a transcription factor from the T-box family that does all kinds of things – some of which (like skeletal development) can be inferred from the symptoms of people with Cousin syndrome, caused by beat-up versions of TBX15.
Probably the selected haplotype results in more brown fat, along with changes in waist-hip ratio and fat distribution. This haplotype is oddly differently from the standard human one, mostly because we picked it up from a population similar to Denisovans. It’s moderately common in Eurasia, very rare in Africa (prolly back-migration) and fixed in the inuit. It’s had hundreds of thousands of years to diverge from the standard AMH haplotype, possibly longer.
These adaptive changes picked up from archaic humans can be different (more complicated) from mutations like sickle-cell, because they can (sometimes)consist of several different linked adaptive substitutions that accumulated over a long, long time. Sickle-cell is recent, and just one nucleotide has changed. More than that, in at least some cases, such as EPAS1 (a Denisovan-origin altitude adaptation allele in Tibetans) the adaptation has progressed: it’s something a bit more sophisticated,not the first solution that came down the pike. The Tibetan adaptation is similar to that seen in mammals that have lived at high altitude for millions of years – while the altiplano adaptation is more like an exaggerated version of individual acclimatization.
Archaic humans had lived in and around the Tibetan plateau for a long time, perhaps as much as two million years. They were the go-to guys for classy altitude adaptations. In much the same way, archaic humans had lived in Eurasia during the Ice Age, freezing their nuts off, for up to two million years. They probably weren’t as good at making warm clothing as anatomically modern humans (Sharp Dressed Man), since they did not make needles. They should have had relatively sophisticated metabolic changes that adapted them to living in an icebox, adaptations worth stealing. There may be other cases like WARS2/TBX15 in the Inuit – and there may be other evolutionarily significant environmental factors (like changes in length of day) that existed in Eurasia and were largely absent from Africa.