How humans got smart: Rush of blood to the head

[Editor’s note: Roger Seymour is professor emeritus of physiology at the University of Adelaide.]

The blood flow to the cognitive part of the brain, the cerebrum, comes through two internal carotid arteries, one on the right and one on the left. The size of these arteries is related to the rate of blood flow through them.

My eureka moment occurred when I realised that the size of an artery can be gauged by the size of the hole in a bone that it passes through.

We found that the size of the carotid canals increased much faster than expected from brain size in 12 species of our human ancestors over a period of 3 million years.

While brain size was increasing 3.5 times, blood flow rate surprisingly increased sixfold, from about 1.2ml per second to 7ml per second.

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This indicates that our brains are six times as hungry for oxygen as those of our ancestors, presumably because our cognitive ability is greater and therefore more energy-intensive.

The GLP aggregated and excerpted this blog/article to reflect the diversity of news, opinion, and analysis. Read full, original post: Humans Got Smarter Through Rush of Blood to Head

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