Forget moon landings and Monet, the invention of the Internet and the discovery of insulin. One Stanford University biologist thinks weve actually become less intelligent since the days our cave-dwelling ancestors roamed the Earth.

In a study recently published in the journal Trends in Genetics, Dr. Gerald Crabtree argues that human intelligence peaked at the time of hunter-gatherers and has since declined as a result of genetic mutations that have slowly eroded the human brains intellectual and emotional abilities.

The argument, which lends weight to the controversial hypothesis that human intelligence is determined by genetics as opposed to the environment, is based on the notion that a large pool of genes must be functioning at full capacity to optimize intellectual and emotional behaviour.

According to Crabtree, intelligence genes were fully functioning in the days of hunter-gatherers, as humans were forced to think critically and creatively to survive. But the shift to agriculture and urbanization, he said, weakened natural selection and opened the door to genetic mutation.

I would wager that if an average citizen from Athens of 1000 BC were to appear suddenly among us, he or she would be among the brightest and most intellectually alive of our colleagues and companions, he said.

But fear not, said Crabtree, as the dumbing-down of humanity is a slow process, with only about two or more harmful mutations sustained in the past 3,000 years. He predicted a technological solution will be found to halt the mutations and thus, the brutish process of natural selection will be unnecessary.

Its a polarizing stance in a field of research long divided by the nature versus nurture debate. While neither is scientifically proven, the idea that intelligence is rooted in genetic has had broad social and political implications, including the controversial eugenics movement.

University of Toronto psychology professor Eyal Reingold, whose research leans toward the nurture argument, described Crabtrees research as quite misleading and said there are more serious threats to intellectual and emotional competency in the 21st century that are environment-based.

When you see events such as children bringing guns to schools and bullying, they are all indications of failure of social competencies and decline in that domain, he said.

Originally posted here:

Are humans getting dumber? One U.S. biologist thinks we’ve got nothing on hunter-gatherers of old