Evolution of lactose tolerance
October 27, 2012 4 Comments
I found this Slate piece on the evolution of Lactose tolerance absolutely fascinating. On the surface, it seems like there was never even any need to evolve this as we had long before been able to consume dairy in the form of yogurt and cheeses. Yet, given it’s amazingly rapid spread through the population, drinking liquid milk clearly conferred huge survival advantages. Researchers are not quite sure what the full story is, but it is intimately tied to the rise of agriculture:
There are no written records from the period when humans invented agriculture, but if there were, they would tell a tale of woe. Agriculture, in Jared Diamond’s phrase, was the “worst mistake in human history.” The previous system of nourishment—hunting and gathering—had all but guaranteed a healthy diet, as it was defined by variety. But it made us a rootless species of nomads. Agriculture offered stability. It also transformed nature into a machine for cranking out human beings, though there was a cost. Once humans began to rely on the few crops that we knew how to grow reliably, our collective health collapsed. The remains of the first Neolithic farmers show clear signs of dramatic tooth decay, anemia, and low bone-density. Average height dropped by about 5 inches, while infant mortality rose. Diseases of deficiency like scurvy, rickets, beriberi, and pellagra were serious problems that would have been totally perplexing. We are still reeling from the change: Heart disease, diabetes, alcoholism, celiac disease, and perhaps even acne are direct results of the switch to agriculture.
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.
In my family, both David (12) and Evan (6) largely owe their continued overall health and growth to prodigious consumption of whole milk (and a daily multivitamin). They are both picky eaters– Evan extremely so. And David has a greatly reduced appetite from the Adderall XR which keeps him (and thus, us) sane. Without all that fat and protein I’m sure they’d both be way malnourished. Hooray for lactose tolerance!