Turns out that our intelligence isn’t only dependent on the brain size, our blood plays an important role too. Since forever, anthropologists have been curious about the evolution of human intelligence through the time, and since then, they always focused on the fossil skull size, and during the time, the volume of our brain have increased to about three and a half times when compared to our ancestors, the Australopithecus.
In general, we just assume that is the intelligence is related to the brain of the size, because the bigger the brain, the larger the number of nerve cells in it.
The new research focused on the blood flow to the brain, which is directly related to the metabolic rate since the blood transports the oxygen, and if that flow to the brain is interrupted, you just pass out within mere seconds.
The usual blood flow to your brain each second is of about 7 millimeters, and this rate suffers almost no variation across different tasks.
The blood flow come to the cerebrum, the cognitive part of the brain, through two internal carotid arteries, located both on the right and the right, and their size is related to the rate of flow that goes through them.
Just as it happens at our houses, where plumbers install larger hoses when a bigger flow needs to pass through, the blood circulatory system adjusts itself during time, and in turn, increases the oxygen flow to meet the organ demand.
By measuring the size of the large arteries that flow blood to the brain, we can actually calculate the average rate of blood flow that goes through the brain and it is as simple as effective.
So, while the brain increased to 3.5 its size, the blood flow rate increase an amazing 6 times, going from about 1.2 millimeters per second to 7! And this indicates that our brains, need 6 times the quantity of oxygen of our ancestors, probably because of our cognitive ability, that requires more energy from our brain.
Our body allocates about 25 percent of its total metabolic rate to the brain, while other primate usually allocates only 10 percent. Our brain acts like a supercomputer, the greater its processing capacity, the greater the energy supply demand, in the brain’s case, the blood flow.
Unlike all other animals, the human brain increased its size faster than the increase on body size, making us unique among all animal.
You can read the whole article on The Conversation.