Understanding Human Adaptation to Cold Climates

Humans have used technology to adapt to the cold. Indeed all living apes are found in the tropics and the oldest known fossils from the human lineage (hominins) come from central and eastern Africa. The hominins who dispersed northwards into higher latitudes had to deal with, for the first time, freezing temperatures, shorter days that limited foraging time, snow that made hunting more difficult and icy wind chill that exacerbated heat loss from their bodies. Sites from more recent settlements, such as Boxgrove in West Sussex, southern England, offer more clues about how ancient hominins survived northern climates. There is good evidence these hominins hunted animals, from cut marks on bones, to a horse shoulder blade probably pierced by a wooden spear. These finds fit with studies of people who live as foragers today which show people in colder regions depend on animal prey more than their warm climate counterparts. Meat is rich in the calories and fats needed to weather the cold. A fossilised hominin shin bone from Boxgrove is robust compared to living humans, suggesting it belonged to a tall, stocky hominin. Larger bodies with relatively short limbs reduce heat loss by minimising surface area.
The Neanderthals, who lived in Eurasia about 400,000-40,000 years ago, inhabited glacial climates. They had short, strong limbs, and wide, muscular bodies suited to producing and retaining heat, as well as a protruding face and beaky nose which was more efficient than those of earlier, warm-adapted species at conserving heat and moisture. Even with their cold-adapted physique, Neanderthals were still hostage to their tropical ancestry and had to develop complex culture to cope, such as making clothes and shelters from animal skins and controlling fire.
The earliest fossils in the Homo sapiens lineage date from 300,000 years ago, from Morocco. But we didn’t spread out of Africa until about 60,000 years ago. Over the intervening thousands of years, people living in freezing cold places have adapted biologically to their environment but on a small scale. One well-known example of this adaptation is that in areas with low sunlight, Homo sapiens developed light skin tones, which are better at synthesising vitamin D. The genomes of living Inuit people from Greenland demonstrate physiological adaptation to a fat-rich marine diet, beneficial in the cold. Our tropical legacy means we would still be unable to live in cold places without developing ways of coping with the temperatures. This human ability to adapt behaviorally was crucial to our evolutionary success.