Wednesday, October 24, 2012

Milk is Murder

Humans are a strange species for many reasons.  Among them, we drink milk our entire lives.  For some reason we continue to produce the enzyme which breaks down lactose.  The linked article demonstrates the strangeness of this and gives a few theories for why this mutation is evolutionarily advantageous, though there is no definitive answer.

Milk was not necessarily an advantage by itself.  That is to say, the milk may have offered no new nutrients, so it was not a better food source (particularly since the common milk derivatives such as yoghurt and cheese have most of the lactose converted anyway, so most people can eat them without the mutation).

I offer this theory: it's not the milk that gave an advantage, but the animals and from them, the disease.  Those who could digest milk would have more reason to keep milk-producing animals around.  They would be the ones who are therefore constantly exchanging disease with animals.  Given their proximity, they'd be more likely to be resistant and survive, relative to those who have little contact with animals and therefore are more vulnerable to cross-species diseases.  While those who had direct contact would be more often sick, those who were not in direct contact would suffer more serious consequences, such as mass death.

We saw this demonstrated on a large scale in the Americas, where the Europeans who had frequent contact with animals and their diseases, and who had suffered terribly for it, did survive them, while the Native Americans were devastated by them.  Could this have happened on a small scale earlier in human history, centered around milk-producing animals?

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