Why Did Our Brains Start Shrinking 20,000 Years Ago?

– Cro-Magnon man, who lived in Europe 20,000 to 30,000 years ago, had the biggest brains of any human species. Today’s human brain is about 10 percent smaller than the Cro-Magnon brain.

About 20,000 years ago our brains started getting smaller and they have been shrinking ever since. Is this a sign we are getting dumber or an evolution process that can be beneficial to the human species?

Scientists are divided on this subject and there are various theories that could explain our shrinking brains.

One possibility, suggested by Christopher Stringer, a paleoanthropologist at the Natural History Museum in London has suggested the shrinking of our brains is related to the decline in humans’ average body size during the past 10,000 years.

A larger body requires a larger nervous system and thus a larger brain. Our shrinking body size can be warmer conditions on the earth in the 10,000 years after the last Ice Age ended. Colder conditions favor bulkier bodies because they conserve heat better. A warmer climate is less physically demanding for our bodies.

Our ancestors required much larger brains because they lived in a very hostile environment. Living conditions for modern humans has changed. Psychology professor David Geary of the University of Missouri thinks that brain size decreased as population density increased. As complex societies emerged, the brain became smaller because people did not have to be as smart to stay alive.

Technology has helped us to store information on computers. We store and process information externally, in books, computers and online and don’t need a large brain that is energetically expensive to maintain. Scientists have proposed that that larger brains may be less efficient at certain tasks, such as rapid computation, because of longer connection pathways.

Brian Hare, an anthropologist at the Duke University Institute for Brain Sciences, thinks the decrease in brain size is not a negative process. On the contrary, it’s evolutionary advantage because it shows we are more “domesticated” and less aggressive. If we look at the animal world, we notice that for example bonobos have smaller brains than chimpanzees and are also much less aggressive.

Many scientists also admit we should not overlook the possibility the shrinking is a sign we are actually getting dumber. The more we rely on technology to do the work for us, the less we think on our own.

The way we live may have affected brain size.

So, there are different scientific theories that could explain our shrinking brain.

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