Black Europeans, Short Spaniards, Tall Swedes, Milk, and Recent Human Evolution
During the past year, genetic studies have revealed some surprises about European prehistory. One study in particular analyzed DNA from 230 skeletons, dating from 6600 B.C. to around 300 B.C. It tells us that Europeans evolved many familiar traits far more recently than we’d thought.
Here are three of the studies’ key discoveries:
- Mysterious Height Divergence: The height of Europeans seems to have taken an odd turn around the time agriculture arrived — about 6000 B.C. Northern Europeans started getting taller, while southern Europeans started getting shorter. No one knows why or what role farming played, if any. (Tall migrants from the Russian steppes boosted northern height, but these Yamnaya people didn’t arrive until around 2800 B.C., more than 3,000 years after the trend began.)
- Recent Black Europeans: Scientists have long believed Europe’s first Homo sapiens had dark skin, like their African forebears. These immigrants began evolving light skin shortly after their arrival, 45,000 years ago — according to the theory — to increase sun absorption in northern lands. Humans need sunlight to produce vitamin D, which protects bones from rickets. Recent analysis, however, reveals that, except in the far north, Europeans still had dark skin as late as 7000 B.C., more than 35,000 years after they arrived. Scientists now think that most of Europe’s hunter-gatherers got enough vitamin D from meat, even with limited sunlight. Instead, it was farming that most decisively led to pale Europeans, starting tens of thousands of years after the initial migration. Prehistoric farmers ate less meat than hunter-gatherers, so presumably they lost the vitamin D supplement they needed to make up for limited sunlight — and grew paler to compensate. (Lighter-skinned Middle Easterners began migrating to Europe around the same time, but scientists think natural selection played a far larger role than migration. Incidentally, my last post, The Backflow into Africa, mentions these Middle Eastern migrants, in the last paragraph.)
- Recent Rise of Lactose Tolerance: Milk evolved to feed babies, and for most of prehistory, few or no adults could digest it. But most modern European adults can digest milk. Anthropologists have long thought lactose tolerance spread when farming began in Europe, around 6000 B.C., as cow’s milk and cheese offered new sources of calories. But recent analysis tell us European lactose tolerance didn’t spread until 4,000 years later, around 2000 B.C. No one knows why lactose tolerance appeared then, or why it didn’t appear earlier.
Europeans probably aren’t the only humans bearing the genetic markers of recent evolution. I suspect more exciting discoveries lie in our near future.
- Photo: Bison from the great hall of polychromes, Altamira cave, Spain
- Genome-wide patterns of selection in 230 ancient Eurasians, Nature (2015)
- How Europeans evolved white skin, Science (2015)
© 2015 by David W. Tollen. All rights reserved.