Humans still evolving as our brains shrink

Decrease has been happening over last 5,000 years, researcher says

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Weighing in at an average of 2.7 pounds, the human brain packs a whopping 100 billion neurons. Every minute, about three soda cans' worth of blood flow through the brain.

By Charles Q. Choi

Evolution in humans is commonly thought to have essentially stopped in recent times. But there are plenty of examples that the human race is still evolving, including our brains, and there are even signs that our evolution may be accelerating.
Comprehensive scans of the human genome reveal that hundreds of our genes show evidence of changes during the past 10,000 years of human evolution.
"We know the brain has been evolving in human populations quite recently," said paleoanthropologist John Hawks at the University of Wisconsin at Madison.
Surprisingly, based on skull measurements, the human brain appears to have been shrinking over the last 5,000 or so years.
"When it comes to recent evolutionary changes, we currently maybe have the least specific details with regard the brain, but we do know from archaeological data that pretty much everywhere we can measure — Europe, China, South Africa, Australia — that brains have shrunk about 150 cubic centimeters, off a mean of about 1,350. That's roughly 10 percent," Hawks said.
"As to why is it shrinking, perhaps in big societies, as opposed to hunter-gatherer lifestyles, we can rely on other people for more things, can specialize our behavior to a greater extent, and maybe not need our brains as much," he added.
Mutations against malaria
In contrast to our limited but growing knowledge regarding the modern evolution of the human brain, the best example we see of evolution of humans in recent history is linked with malaria, Hawks said.