What I’ve been thinking might actually be going on is that adolescence is something unavoidable that emerges not because it’s so cool and adaptive, but because the adaptive thing is wait a long, long time before you have fully wired up your frontal cortex. Why might that be the case? Alright, so we’re born with our genome, the combination of your mother and father’s genes, that wind up in that first fertilized egg and that’s it. That’s your genetic legacy. Every cell in your body is destined to have that exact same genome. That turns out not to be true in all sorts of interesting ways, but what that also means is that when you’re thinking about what genes have to do with the brain behavior, by definition critically, if the frontal cortex is the last part of the brain to develop it’s the part of the brain least shaped by genes, and most sculpted by the environment and experience. And I think basically the only way you can have a species that is as complex and socially resilient and socially context dependent and all those amazing things we do, the only way you can pull that off is to have a frontal cortex whose development just bears the imprint of everything you experienced along the way—in effect, that’s been freed from whatever extent the genes are deterministic, which is not very. I think ironically what the evolution of the frontal cortex has been about is genetic evolution to free it as much as possible from the straight jacket of genes.
What’s the purpose of breaking free of our genes?
Well, when you look at the sociology of humans, of primate species, when you look at evolution, when you look at anthropology, cross-cultural differences, etcetera—being smart is a useful thing evolutionarily. Primates definitely have an advantage over stickleback fish in terms of the size of their nervous systems. Having a good memory is good, learning a lot, motoric coordination. When you look at the really fancy stuff about social behavior and what determines “success” in sort of the broadest sense of the term, what it’s got to do is appropriate social behavior. You know in the human realm that’s that whole world of your social intelligence is a better predictor of how you’re going to do by all sorts of measures in life than your IQ. You look at a baboon and you ask, “Okay, a male baboon. What determines whether or not you wind up being the alpha in your troop?” Mostly, your muscle mass, how sharp your canines are, how aggressive of a son of a bitch you are. Okay, that’s got tons to do with whether you attain alpha-ship. What’s the predictor of who maintains it for a long time? It’s all social intelligence. It’s who you can intimidate without actually getting into a fight. It’s which coalitions you form and which ones you don’t go anywhere near. It’s which provocations you walk away from. It’s all about impulse control. And when you look at the really complex primates, success is really not about remembering that, “Oh four valleys over there’s a tree that’s going to be fruiting at this time of year; let’s go there this morning.” It’s the social intelligence stuff and what that’s all about is the frontal cortex. If you don’t have a frontal cortex that has been shaped by the subtleties and the idiosyncrasies of your immediate social world, you’re not going to be anywhere near successful of a primate. And I think that’s why it’s got to be the part of the brain that’s the last to develop. It’s got to be shaped by all that contextual stuff.
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