How Smart is That?

As the first significant snowfall of the season turns the local streets beyond my window into a bumper-cars arena, I once again question the sense living in a northern state. It’s the same question I’ve asked myself each winter for decades. I’ve yet to come up with a good answer, thereby giving credence to Claudette Colbert’s assertion in The Palm Beach Story (1942): “Anyway, men don't get smarter as they get older. They just lose their hair.”

Whether our species as a whole is getting brighter as it ages is a question that vexes scientists. The popular science journals sometimes report one way and sometimes the other. Professor James Flynn, for one, believes that the increase in raw IQ test scores in the past 100 years indicates a change that is at least partly biological (see earlier post: All in All, I’d Rather Be Errol ), whether due to improved nutrition, epigenetic factors, or some other influence. Others dismiss the improved scores as an artifact of education; they argue that people today simply are more accustomed to taking standardized IQ-like tests, and so do better at them. True underlying intelligence, they say, is in long-term decline. In the latter camp are paleontologists David Geary and Drew Bailey who note that skeletal evidence shows that cranial capacity peaked 20 000 years ago (see earlier post The Incredible Shrinking Brain ); since then, brain size has shrunk, and by a significant amount. The biggest drop occurred between 15 000 and 10 000 years ago, but did not stop there.

This past week the “getting stupider” hypothesis was in the news again thanks to Gerald Crabtree, a geneticist at Stanford University. In an article in the journal Trends in Genetics, Crabtree reiterates the physical evidence and adds, "A hunter-gatherer who did not correctly conceive a solution to providing food or shelter probably died, along with his or her progeny, whereas a modern Wall Street executive that made a similar conceptual mistake would receive a substantial bonus and be a more attractive mate. Clearly extreme selection is a thing of the past." In short, dunces aren’t culled out. He notes that, even without reverse selection, failure to weed out dimmer bulbs will result in a downward genetic drift due to normal mutation rates in the genetic code. If between 2000 and 5000 genes are involved in intelligence (the generally accepted range), each of us should be carrying two or more maladaptive mutations that arose with the past 3000 years: "If selection is only slightly relaxed, one would still conclude that nearly all of us are compromised compared to our ancient ancestors of 3,000 to 6,000 years ago."

Crabtree has evoked numerous rebuttals, mostly on the grounds that his article is speculative and that his arguments aren’t testable.

So which is it? Are we brainier than our great grandparents or are we halfway down the slide to the future portrayed in Idiocracy? Are the two mutually exclusive – which is to say, could we not, by training and education, be doing more with less? I tend to the “dumber but better educated” view based purely on personal observation, but I could be wrong.

I recommend re-visiting Euripides, Thucydides, and Plato before deciding whether we are brighter than our ancestors. If nothing else, those ancient Greeks were smart enough to live in a Mediterranean climate.

Perhaps Not All of Our Paleo Predecessors Were Brainiacs (double-click for full-screen)