The impact of these mutations remains uncertain, but many scientists say it is plausible that our temperament or reasoning abilities shifted as a result.Numerous phone calls later, it dawns on me that the world’s foremost experts do not really know why our organ of intellect has been vanishing.On that basis, Stringer says, our ancestors were presumed to have the same raw cognitive horsepower.
More important, analysis of the genome casts doubt on the notion that modern humans are simply daintier but otherwise identical versions of our ancestors, right down to how we think and feel.
Over the very period that the brain shrank, our DNA accumulated numerous adaptive mutations related to brain development and neurotransmitter systems—an indication that even as the organ got smaller, its inner workings changed.
Possibly owing to said shrinkage, it takes me a while to catch on. “It certainly gives you a different perspective on the advantage of a big brain,” he says.
After meeting with Hawks, I call around to other experts to see if they know about our shrinking brain.
Consequently, their large brains have often been attributed to brawniness rather than brilliance.
In support of that claim, one widely cited study found that the ratio of brain volume to body mass—commonly referred to as the encephalization quotient, or EQ—was the same for Cro-Magnons as it is for us.
The more I learn, the more baffled I become that news of our shrinking brain has been so underplayed, not just in the media but among scientists.
“It’s strange, I agree,” says Christopher Stringer, a paleoanthropologist and expert on human origins at the Natural History Museum in London.
Geneticists who study the evolution of the human genome seem as surprised as I am (typical response: “No kidding!
”), which makes me wonder if I’m the world’s most gullible person. As I soon discover, only a tight-knit circle of paleontologists seem to be in on the secret, and even they seem a bit muddled about the matter.
As the planet warmed, selection might have favored people of slighter stature.