June 11, 2005


Over at LanguageLog, Mark Liberman contemplates the latest theory for the evolution of language ("it's all about cutting up dead elephants"), and raises a worry I've often had about the evolution of human intelligence in general.

In my opinion, the biggest mystery is not why we humans developed language, but why nobody else did. If language is so great, why doesn't everybody have one -- or at least the best approximation they can manage? Judging by their contemporary descendents, the cephalopods of 400 million years ago probably had as many qualitatively different communicative displays as chimpanzees do. Since then, surely, many other species have gotten into situations that motivated symbolic communication for fission-fusion scavenging, or for social group maintenance, or for sexual display, or whatever.

This is exactly right. One needs to explain not just why human beings have language, but also why other species do not — why can't lions talk? They are, after all, a highly social, sexually-reproducing species engaging in group food-procurement on the African savannah. Similarly, remarkably few accounts I've read of human evolution try to explain why other primate, or at least other great ape, lineages didn't themselves develop human-level cognitive abilities. Maybe all the possible selective forces Liberman talks about, and more, actually work, but they are all very weak, and for some reason only hominids were subject to enough of them to make intelligence or language cost-effective...

Update: In e-mail, Bill Tozier reminds me I have neglected the decisive factor in the evolution of the human mind.

The Natural Science of the Human Species

Posted at June 11, 2005 10:20 | permanent link

Three-Toed Sloth