Monday, October 29, 2012

The strange case of the milk-drinking ape

Most adult humans cannot drink milk. Modern Europeans are the exception. Lactose intolerance is a matter of genetics, genetics which began to change in Turkey around 10,000 BCE, according to an article in Slate. Then
In an evolutionary eye-blink, 80 percent of Europeans became milk-drinkers; in some populations, the proportion is close to 100 percent. (Though globally, lactose intolerance is the norm; around two-thirds of humans cannot drink milk in adulthood.) The speed of this transformation is one of the weirder mysteries in the story of human evolution, more so because it's not clear why anybody needed the mutation to begin with. Through their cleverness, our lactose-intolerant forebears had already found a way to consume dairy without getting sick, irrespective of genetics.
If you let milk sit for only a few hours, the lactose begins to ferment out as milk becomes first yogurt and then cheese.
Analysis of potsherds from Eurasia and parts of Africa have shown that humans were fermenting the lactose out of dairy for thousands of years before lactose tolerance was widespread. Here is the heart of the mystery: If we could consume dairy by simply letting it sit around for a few hours or days, it doesn't appear to make much sense for evolution to have propagated the lactose-tolerance mutation at all, much less as vigorously as it did. Culture had already found a way around our biology. Various ideas are being kicked around to explain why natural selection promoted milk-drinking, but evolutionary biologists are still puzzled.
Whatever the adaptive reason for lactose tolerance among adults, it spread with the emergence of agriculture and the move to cities.
Meanwhile, agriculture's alter ego, civilization, was forcing people for the first time to live in cities, which were perfect environments for the rapid spread of infectious disease. No one living through these tribulations would have had any idea that things had ever been, or could be, different. Pestilence was the water we swam in for millennia.

It was in these horrendous conditions that the lactose tolerance mutation took hold. Reconstructed migration patterns make it clear that the wave of lactose tolerance that washed over Eurasia was carried by later generations of farmers who were healthier than their milk-abstaining neighbors. Everywhere that agriculture and civilization went, lactose tolerance came along. Agriculture-plus-dairying became the backbone of Western civilization.
H/t Tyler Cowen.

1 comment:

  1. I dont know what the importance of this is
    its one of those wierd-o-facts that takes place in Jeopardy

    we cut down reality into small pieces and then wonder why did this happen?

    "oh honey I don't see a forrest here
    did you say we got into a forrest?"

    a lot of flashy writing there and no real essense

    he wrote all that to tell us that cheese is made from milk?

    i dont buy that gene theo-sophy, that's certain

    another tool to play around with

    we know at 10,000 or a few thousand before that people got the sheeps and the goats into herds

    and they drunk their milk or maybe they didnt

    this kind of writing is what pricks your nerves

    going around in circles saying nothing and now he can be proud he wrote the important philosophical treatise

    people drink the milk and all its byproducts because it makes them strong

    so what of it?

    for their betterment

    what of it??