Our Brains Are Shrinking. Are We Getting Dumber?

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Our Brains Are Shrinking. Are We Getting Dumber?

PostPosted by verdilak » Sat Jan 08, 2011 3:34 am

http://www.npr.org/2011/01/02/132591244/our-brains-are-shrinking-are-we-getting-dumber wrote:When it comes to brain size, bigger doesn't always mean better. As humans continue to evolve, scientists say our brains are actually getting smaller.

The downsizing of human brains is an evolutionary fact that took science writer Kathleen McAuliffe by surprise.

"I said, 'What? I thought it was getting bigger!'" she tells NPR's Jacki Lyden. That was the story up to 20,000 years ago, she learned. Then, the brains of our ancestors reversed course and started getting smaller — and they've been shrinking ever since.

Cro-Magnon man, who lived in Europe 20,000 to 30,000 years ago, had the biggest brains of any human species. In comparison, today's human brain is about 10 percent smaller. It's a chunk of brain matter "roughly equivalent to a tennis ball in size," McAuliffe says.

The experts aren't sure about the implications of this evolutionary trend. Some think it might be a dumbing-down process. One cognitive scientist, David Geary, argues that as human society grows increasingly complex, individuals don't need to be as intelligent in order to survive and reproduce.

But not all researchers are so pessimistic. Brian Hare, an anthropologist at the Duke University Institute for Brain Sciences, thinks the decrease in brain size is actually an evolutionary advantage.

The Domesticated Brain

"A smaller brain is the signature of selection against aggression," Hare tells Lyden. "Another way to say that is an increase in tolerance."

Hare says when a population selects against aggression, they can be considered to be domesticated. And for a variety of domesticated animals like apes, dogs or turkeys, you can see certain physical characteristics emerge. Among these traits are a lighter and more slender skeleton, a flattened forehead — and decreased brain size.

Hare's studies focus on chimpanzees and bonobos. In evolutionary terms, they are much like humans, but are physically quite different from one another. Bonobos have smaller brains than chimpanzees — and are also much less aggressive.

While both have the cognitive ability to solve a given puzzle, Hare says, chimpanzees are much less likely to accomplish it if it involves teamwork. Not so with bonobos.

"If the food is quite sparse and it's not easy to share, [bonobos] can solve the problem," Hare says. "Chimpanzees, in that same context — where there's not much food and it's not easy to share — they just refuse to work together. They can't solve the problem, even though they know how."

Hare does admit that the shrinking human brain could signal an evolutionary dumbing-down, but more important is what the phenomenon tells us about ourselves. Comparing our evolution to that of other animals enriches our understanding of the human condition.

"The nice thing about studying animals and human nature," Hare says, "is that it helps us design or think of some strategies that deal with our darker sides."

An advantage to having a smaller brain? What with it coinciding with the advent of agriculture, which was itself responsible for humans losing an average of 6 inches of height that we are only just now starting to regain.... I don't believe there is anything advantageous to having a smaller brain.

Barry Groves, PhD has a rather interesting take on it:

http://www.second-opinions.co.uk/vegetarians-have-smaller-brains.html wrote:With such a small gut with which to absorb all the nutrients and energy our bodies need, a modern low-calorie, low-fat, fibre-rich, plant-based diet is woefully inadequate as an energy source for our energy-hungry system to function at peak efficiency. That lack has begun to show.

Since the advent of agriculture, there has been a worrying trend as our brains have actually decreased in size. A recently updated and rigorous analysis of changes in human brain size found that our ancestors' brain size reached its peak with the first anatomically modern humans of approximately 90,000 years ago. That then remained fairly constant for a further 60,000 years.[11] Over the next 20,000 years there was a slight decline in brain size of about 3%. Since the advent of agriculture about 10,000 years ago, however, that decline has quickened significantly, so that now our brains are some 8% smaller.
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