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Blood thirsty brains

- Wits Communications

New research by the Brain Function Research Group at Wits and the University of Adelaide challenges views of human intelligence

A research collaboration between the University of the Witwatersrand and the University of Adelaide in Australia has discovered that the human brain evolved to become not only larger but more energetically costly and blood thirsty than previously believed.

The research team, led by Prof. Emeritus Roger Seymour from the University of Adelaide, today published a paper in Royal Society Open Science, which challenges previously held views on the evolution of the human brain.

The study, which facilitated new collaborations between the Brain Function Research Group and the Evolutionary Studies Institute at Wits University with the Cardiovascular Physiology team in the School of Biological Sciences at the University of Adelaide, challenges previous theories that human intelligence progressed simply due to increased brain size.

The research shows that while brain size has increased by some 350% over human evolution, blood flow to the brain increased an incredible 600%. Dr Edward Snelling of the Brain Function Research Group at Wits and co-author of the study, says: “Ancient fossil skulls from Africa reveal holes where the arteries supplying the brain passed through.  The size of these holes show how blood flow increased from 3-million-year-old Australopithecus to modern humans. Before now, the intensity of brain activity was believed to have been taken to the grave with our ancestors!”

The increases in the supply of blood to the brain appear to be more closely linked to the evolution of human intelligence, where the human brain has evolved to become not only larger but more energy demanding and blood thirsty than previously believed.

Prof. Seymour and his research team calculated how blood flowing to the brain of human ancestors changed over time, using the size of two holes at the base of the skull that allow arteries to pass to the brain.  Because of the strong link between the flow of blood to the brain and cognitive function, the team was able to track the increase in human intelligence across evolutionary time.

“To allow our brain to be so intelligent, it must be constantly fed oxygen and nutrients from the blood. The more metabolically active the brain is, the more blood it requires, so the supply arteries are larger.  The holes in fossil skulls are accurate gauges of arterial size. We believe this is possibly related to the brain’s need to satisfy increasingly energetic connections between nerve cells that allowed the evolution of complex thinking and learning,” says Prof. Seymour.