Our Brains Are Shrinking. Are We Getting Dumber? When it comes to brain size, does bigger always mean better? As humans continue to evolve, scientists say our brains are actually getting smaller.

Our Brains Are Shrinking. Are We Getting Dumber?

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Now while the Large Hadron Collider is smashing atoms and blowing scientific minds, research shows that we, as a species, are actually seeing our brains get smaller.

Kathleen McAuliffe writes about human evolution for Discover Magazine, and she stumbled upon this story of the amazing shrinking brain while researching a different story.

Ms. KATHLEEN McAULIFFE (Writer, Discover Magazine): Well, I was interviewing the anthropologist John Hawkes about his genetic research related to human evolution when he added, just sort of as a casual aside, that the human brain is shrinking. And I said, what? I thought it was getting bigger.

And he said, no, that was true for two million years of our evolution. But then about 20,000 years ago, there was a reversal. And our brain has been getting smaller and smaller ever since.

LYDEN: Wow. That is really shocking. How much smaller are our brains from those of our ancestors?

Ms. McAULIFFE: Well, they - humans who had the largest brains are the Cro-Magnons, who lived 20 to 30,000 years ago in Europe. The missing chunk of brain matter is roughly equivalent to a tennis ball in size. That's about a 10 percent shrinkage.

LYDEN: What are the implications of this as a species? Are we dumbing down?

(Soundbite of laughter)

Ms. McAULIFFE: Well, the funny thing is that even the experts don't know for sure.

LYDEN: Now in your article for Discover, you focused on a researcher named Geary. How did he see this?

Ms. McAULIFFE: David Geary, he is a cognitive scientist at the University of Missouri. And he subscribes to the idiocracy theory. Did you ever see the film "Idiocracy?"

(Soundbite of movie, "Idiocracy")

Unidentified Man: As the 21st century began, human evolution was at a turning point.

Ms. McAULIFFE: A perfectly average guy called Joe.

(Soundbite of movie, "Idiocracy")

Mr. MICHAEL McCAFFERTY (Actor): (as Officer Collins) Gentlemen, meet Joe Bauers, our first subject for the human hibernation experiment.

Ms. McAULIFFE: And when he wakes up 500 years later, he finds himself on a dumbed-down planet where he's easily the smartest person around.

(Soundbite of movie, "Idiocracy")

Mr. TERRY CREWS (Actor): (as President Camacho) So you're smart, huh?

Mr. LUKE WILSON (Actor): (as Joe Bauers) No, no.

Mr. CREWS: (as President Camacho) I thought your head would be bigger.

Ms. McAULIFFE: And Geary thinks something a little bit like this happened to us. Just around the time when we see brain size decreasing, the human population is going from very sparse to dense in different parts of the world, and it's just at that point when you're seeing the beginnings of society springing up. And there's more division of labor, more complex interactions between people. Trade springs up between groups. And so you don't have to be as smart to stay alive.

LYDEN: Kathleen McAuliffe, her article in Discover Magazine is on the shrinkage of the human brain.

Thank you.

Ms. McAULIFFE: Well, thank you.

LYDEN: So there's a scientist who thinks he can explain why the human brain has been shrinking and why that might not even be a bad thing. His name is Brian Hare, and he's an anthropologist at Duke University, who studies the great apes.

He says that as animal species become domesticated, their brains generally get smaller.

Professor BRIAN HARE (Institute for Brain Sciences, Duke University; Anthropologist): So whether you're talking about a turkey, a dog or a cat, you have not just less aggression and more playful behavior, but you have an animal that, relative to the wild type, it has a smaller brain.

LYDEN: Well, what about cooperation, which all really human endeavor is going to depend on, more or less? You've looked at apes and chimps, as we said. You found that a smaller brain can actually mean a better ability to work together. Why is that?

Prof. HARE: Well, if we look at our two closest relatives, bonobos and chimpanzees, bonobos being the tolerant and less aggressive of the two ape species, what's interesting is even though bonobos have a smaller brain - and some people might argue because of that they should be less intelligent - when we give them a problem where they have to work together, it ends up that bonobos can solve the problem in contexts where chimpazees can't.

Let's say there's food that's out of reach, and you have to pull it within reach, and you have to work together, two individuals, to pull it within reach, well, bonobos, even if the food is quite sparse and it's not easy to share, they can solve the problem, whereas chimpanzees, in that same context where there's not much food and it's not easy to share, well, they just refuse to work together. And they can't solve the problem, even though they know how.

So again, who's smarter?

LYDEN: It just says that a lot of intelligence is relative.

Prof. HARE: That's right. The smaller brain in modern humans may be evidence that we can cooperate, and we have tolerance that you may not have seen in archaic Homo or in Neanderthals.

LYDEN: You've given hope to so many.

(Soundbite of laughter)

LYDEN: That's Brian Hare, an anthropologist who studies domestication of great apes at the Duke Institute for Brain Sciences.

Thank you.

Prof. HARE: Thank you very much.

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