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Well, if that’s all you mean by human evolution …


In “A New Kind of Social Science for the 21st Century: A Conversation with Nicholas A. Christakis” (The Edge, 8.21.12, transcript and vid), physician and social scientist Christakis muses,

Another example of this tension between whether things are changing or not changing is the debate about whether or not human beings can evolve in historical time, under the pressure of historical forces. I used to think that this was not possible. But there’s been a huge amount of work by many labs around the country in the last 10 years or so documenting that we humans are evolving in real time.

The famous, best example of this is the evolution of lactase persistence into adulthood. The ability to digest lactose, which is a sugar in milk, isn’t really of any value in adulthood until you have a stable source of milk. It turns out that human beings have independently evolved this capacity to digest milk as adults a half-dozen times, in different settings around the world, coincident with the cultural innovation of domesticating animals—domesticating sheep, goats, or cows, which provides a ready supply of milk. This milk is a good food source in times of scarcity. It’s also a good source of unspoiled hydration. So this confers survival advantages.

If “human beings have independently evolved this capacity to digest milk as adults a half-dozen times, in different settings around the world,” in recent history, one suspects that in the absence of milk, the trait would disappear again, only to be revived later in a dairying culture. In what sense is this evolution, as opposed to drawing on a library of existing traits?


Why do we humans have friends? It’s not hard to understand why we have mates. It’s not hard to understand why we seek out others with whom to have sex. It’s quite another to explain why do we have friends? We’re very unusual as a species in doing this. Other species, generally speaking, don’t do this; they don’t form long-term, non-reproductive unions to other members of their species.

Not only do we have friends, but we have friends in very particular ways, it turns out. As a result of this, we form networks, social networks, with very particular structures. James and I have been engaged in a project, and will continue to be working in this area over the coming five years, trying to understand the biological origins of human sociality and human network structure and function. Why do networks have the structure that they do, and why do networks perform the functions that they do, for us as a species? Hence, the first big issue that we are engaged in is the biological origin of social order, and this is focused, in particular, or at least initially, on networks.

If “ Other species, generally speaking, don’t do this,” why is he looking to biology for answers?

Oh wait. His lab has a grant. That changes everything.

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Hijacking this thread somewhat, but re the quote I cite below from the article on Carl Zimmer's intellectual AWOL (absent without leave): 'That's awkward for publisher and author alike. The lesson, I think, is always to be careful about keeping up with the relevant scientific literature. For the sake of students who read his textbook, let's hope Carl Zimmer is doing that.' ...'relevant' being the operative word, Carlo. You must wean yourself of evamolutionism. Axel

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