Monday, September 12, 2005

Coming to a Big Skull Near You

Finally, after a long dreary dry spell, there's some good news about the state of the human brain.

Our brains are evolving. That's generally a good thing.

It also seems pretty bizarre the way things have been going over the past few thousand years. Scientists are also not sure in what direction brains are evolving.

Actually, they aren't sure of much, except that two brain genes seem to have been changing rapidly since humans stumbled on agriculture and written language.

Howard Hughes Medical Institute researchers at the University of Chicago found that two "new" versions of the genes arose about then.

Now here's the puzzling part: one of the genes is called "microcephalin" and the other is "abnormal spindle-like microcephaly." As their names suggest, mutations in these genes can cause a syndrome in which the brain develops to a much smaller size than normal.

Presumably, the unmutated versions of these genes have something to do with determining the size of the brain. What is that something?

The internal dimensions of the skull have a lot to do with the size of the brain, too. That is, cranial volume is an upper limit. So for brains to get any bigger the skull is also going to have to do some evolving.

It's happened before, but not in a long time.

The researchers are also careful to point out that larger doesn't necessarily mean smarter.

The other big question is what is the selective pressure that is changing the two genes? It's not like "smarter" people possess some recognizable advantage. On the contrary, intellect doesn't seem to count for much these days.

The average American is more likely to be able to explain football and stock car racing than name a single philosopher, poet, mathematician, painter, novelist or scientist.

Maybe humans are bifurcating into two species, a neo-Neanderthal country-western, Maxim-reading, SUV-driving big guy, and a book-worm, chess-team, Mozart-listening, small guy.

Who gets the big brain?

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