Stanford University geneticist Gerald Crabtree contends an average Greek from 1000BC, if brought to the present, would be one of the smartest on earth.

At the crux of his theory, which he admits in two journals published in Trends in Genetics could do with some testing, is how punishment has evolved, in particular for the crime of stupidity – when our ancestors did something stupid, the punishment was more than likely death, raising the evolutionary stakes for the humans long before us.

Crabtree explains: “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.”

With a theory based on the amount of genes that contribute to our intellectual ability and the number of mutations that can impact those genes negatively over time, he concludes we reached out peak of intelligence long ago.

“We, as a species, are surprisingly intellectually fragile and perhaps reached a peak 2,000 to 6,000 years ago,” Crabtree writes. “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.”

He does admit this could all be proven wrong, if we still had the intellect to do so. But it’s not all bad news.

“Remarkably it seems that although our genomes are fragile, our society is robust almost entirely by virtue of education, which allow strengths to be rapidly distributed to all members,” he says.

Image via Getty