Drinking Milk

Most adult humans can't digest milk. But some can. As the map above shows, the mutation that causes adults to keep producing lactase originated in at least three different places, possibly four. One of them seems to be in northern Europe. Which certainly makes sense; off the top of my head I might have chosen Denmark as the most dairy-centric place in the old world.

But a bunch of European archaeologists have been studying the origins of our milk-using culture, and they have just come out with a paper arguing that dairying arose in the Middle East and spread to Europe with farming. They base their conclusions on the age of cattle bones: if you are dairying you kill the male calves while they are young, so the mothers will keep giving milk, whereas if you are not dairying you wait for the males to reach full size before killing them. They observe the dairying bone pattern in both cows and goats at archaeological sites in the Middle East dating back to 10,000 years ago.

If so, this raises the question of what they were doing with all the milk that adults couldn't consume. There isn't any evidence for the making of hard cheese (which has no lactose) that early, so presumably they were feeding the milk to children. Did the use of cow's or goat's milk as a supplemental baby food allow early weaning, which then triggered the population growth that sent those early farmers spreading into Europe and across Asia?

Pondering this map, though, I wonder if it doesn't undermine this whole genetic scheme. Why are 10% of Chinese and 20% of Japanese adults lactose tolerant? How did the genes get there?

As with everything else about our genetic history, there are a lot of complications here that haven't been explained and may never be.