Suppose you take a few species of apes that lived in Africa about ten million years ago. Think of these species as nearly identical, but seperate populations. Now turn loose on each species the force of runaway sexual selection—an evolutionary positive feedback loop of genetic traits and the mating preference for those traits. One species might develop a runaway preference for large muscles, and turn into gorillas. Another might develop a runaway preference for constant sex, and turn into bonobos. A third species might develop a runaway preference for intelligence, and turn into us.
Intelligence is a fitness indicator, which might be why we have it. Animals use them to judge potential mates. The brain—like a gigantic shiny colorful tail—is a good choice. It’s sensitive to the animal’s condition, it’s hard to fake, and it’s a pretty good show of what sexy genes you have. A mind gets pretty screwed-up if you have a screwed-up existence—and crazy isn’t sexy. Conversely, a good mind is, and it shows. Story-telling, humor, playfulness, creativity, wit, kindness, a broad vocabulary, social savvy, imaginative problem-solving, and refined taste are all mental fitness indicators used by humans. All these sexy personality traits lead to more sexy persons, the better brain genes making minds bigger and better.
That’s the idea behind Geoffrey Miller’s The Mating Mind, in particular the chapter appropriately called “A Mind Fit for Mating.” Pages 77 and 111 are partially (and liberally) paraphrased above. His hypothesis is that our swollen primate cerebellums are the result of a sexual fetish preference our ancestors were lucky enough to stumble upon. And because our courtship (and brain evolution) got so carried away with itself, we very accidentally discovered all these really cool survival mechanisms like agriculture, language, architecture, metal-working, medicine, and the other stuff you can research in Civilization. Even more astounding is that all the quintessentially human self-expressives like literature, art, philosophy, music, dance, and making comic books are for mating purposes just ornamentation to show off our big sexy brains.Sexy brains read more of my blog.