Smarter brains are blood-thirsty brains

August 30, 2016
Skull casts from human evolution. Left to right: Australopithecus afarensis, Homo habilis, Homo ergaster, Homo erectus and Homo neanderthalensis. Credit: Roger Seymour. Casts photographed in the South Australian Museum.

A University of Adelaide-led project has overturned the theory that the evolution of human intelligence was simply related to the size of the brain—but rather linked more closely to the supply of blood to the brain.

The between Australia and South Africa showed that the evolved to become not only larger, but more energetically costly and blood thirsty than previously believed.

The research team calculated how blood flowing to the brain of changed over time, using the size of two holes at the base of the skull that allow arteries to pass to the brain. The findings, published in the Royal Society Open Science journal, allowed the researchers to track the increase in across .

"Brain size has increased about 350% over human evolution, but we found that blood flow to the brain increased an amazing 600%," says project leader Professor Emeritus Roger Seymour, from the University of Adelaide. "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.

"To allow our brain to be so intelligent, it must be constantly fed oxygen and nutrients from the blood.

Human skulls, showing the location of two openings for the internal carotid arteries that supply the cerebrum of the brain almost entirely. The sizes of these openings reveal the rate of blood flow, which is related to brain metabolic rate and cognitive ability. Credit: Edward Snelling. Sourced from the Raymond Dart Collection of Human Skeletons, School of Anatomical Sciences, Faculty of Health Sciences, University of the Witwatersrand.

"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."

The study was a new collaboration between the Cardiovascular Physiology team in the School of Biological Sciences at the University of Adelaide and the Brain Function Research Group and Evolutionary Studies Institute at the University of the Witwatersrand.

Co-author Dr Edward Snelling, University of the Witwatersrand, 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 three million-year-old Australopithecus to modern humans. The intensity of brain activity was, before now, believed to have been taken to the grave with our ancestors."

Honours student and co-author Vanya Bosiocic had the opportunity to travel to South Africa and work with world renowned anthropologists on the oldest hominin skull collection, including the newly-discovered Homo naledi.

"Throughout evolution, the advance in our brain function appears to be related to the longer time it takes for us to grow out of childhood. It is also connected to family cooperation in hunting, defending territory and looking after our young," Ms Bosiocic says.

"The emergence of these traits seems to nicely follow the increase in the 's need for blood and energy."

Explore further: You need this hole in the head—to be smart

More information: Fossil skulls reveal that blood flow rate to the brain increased faster than brain volume during human evolution, Royal Society Open Science, rsos.royalsocietypublishing.or … /10.1098/rsos.160305

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brahmix
not rated yet Aug 31, 2016
Curious thing: as a teenager I realized that when I went into _mental overdrive_ (mentat!) state, I generally get all flushed as the blood rush to my head, lovely red blotches mostly on my throat and neck. I concluded back then that this blood supply is not binary but more like VBR (like mp3 encoding) - sometimes you need more, mostly you don't. The holes therefore indicate a _maximum_ flow rate, and not a general or fixed flow.

This is therefore a great study for me to read as now I know that the morphology of the skull must be able to allow this *boosting*. The flush, I believe, is simply because the arteries are not dedicated pipes, but networks which will supply excess blood to some part in the region of transport.

Cheers!
someone11235813
not rated yet Aug 31, 2016
This is not new! I heard about this in a lecture series years ago.
tinitus
Aug 31, 2016
This comment has been removed by a moderator.
HTK
not rated yet Aug 31, 2016
Hmmm.. apparently the oriental average brain size is 10% larger I saw on BBC Horizon.
tmarksur
not rated yet Aug 31, 2016
"Why we should expect, that the larger and more complex brain would require less oxygen and blood?" It's about blood flow increase COMPARED to size increase. The need for blood increased way more than the size did. And that is far from trivial.
tinitus
Aug 31, 2016
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tmarksur
not rated yet Aug 31, 2016
"Any conclusions?" Yes. Women then seem to have better connected and efficient brains, and as such manage to be similarly capable in cognitive tasks.
tinitus
Aug 31, 2016
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Thorium Boy
not rated yet Sep 01, 2016
"Any conclusions?" Yes. Women then seem to have better connected and efficient brains, and as such manage to be similarly capable in cognitive tasks.


Unfortunately, not borne-out by real-life accomplishment, in any field requiring intelligence, creativity, spacial cognition.
Whydening Gyre
not rated yet Sep 01, 2016
Brain size has increased about 350% over human evolution, but we found that blood flow to the brain increased an amazing 600%
Actually what was observed was the increasing of the foramina carotid diameter. Carotid arteries in women are smaller even after adjusting for body and neck size, age, and blood pressure. Any conclusions?

Do you seen the similarity to caloric input and longevity?
Women live longer... hmmmm...
tmarksur
not rated yet Sep 01, 2016
Unfortunately, not borne-out by real-life accomplishment, in any field requiring intelligence, creativity, spacial cognition.
True. But this isn't really relevant i think. There is no female Kasparov, Magnus Carlsen, Albert Einstein, Vettel , Hawking or whatever. But women on average do as well as men in tasks requiring intelligence, creativity etc.
StudentofSpiritualTeaching
not rated yet Sep 03, 2016
There is no woman Stalin, Hitler, Saddam Hussein, Nero and what have you. What does that tell us? They are the better leaders for mankind. Count on it that over the millennia there have been the same number of female geniuses, but just very humble, typically suppressed by men, not power hungry and therefore invisible for historians.
tinitus
Sep 03, 2016
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4johnny
not rated yet Sep 04, 2016
What about heart size, strength, rate?
4johnny
not rated yet Sep 04, 2016
What about heart size, strength, rate?
4johnny
not rated yet Sep 04, 2016
What about blood vessel wall thickness, stretchability, etc?

Seems to me that the variate a have not been well isolated.

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