Imagine a caveman who never worried about anything. Carefree Thrag might have happily eaten handfuls of unfamiliar berries, marched curiously up to a sabre-toothed cat, or, at the least, wouldn't have troubled himself over how to impress the comely Frakkina. In other words, a caveman who never worried wouldn't have passed his genes on to us. New research suggests that worry may have coevolved with intelligence in humans, a sign that Thrag's smarter, more brooding cousins were indeed better candidates for survival.

"While excessive worry is generally seen as a negative trait and high intelligence as a positive one, worry may cause our species to avoid dangerous situations, regardless of how remote a possibility they may be," said Jeremy Coplan, professor of psychiatry at SUNY Downstate. "In essence, worry may make people 'take no chances,' and such people may have higher survival rates. Thus, like intelligence, worry may confer a benefit upon the species."

Researchers compared patients with generalized anxiety disorder (GAD) and healthy volunteers on IQ, worry, and the metabolism of the nutrient choline in the brain. Among the volunteers with GAD, there was a strong correlation between IQ and level of worry, both of which were correlated with choline metabolism. Those without GAD showed the opposite correlation.

Worrying may have saved Thrag's companions, but does it hinder us now? Too much worrying is stressful, and our high-octane, high-stimulation lives probably worry us more chronically than those of our ancestors. Perhaps the most intelligent of us shouldn't worry so much. After all, we made it this far.

Read more