Hole in head makes you smarter

Melbourne: Intelligence in humans can be estimated by the size of the holes in the skull through which the arteries pass, says a study."It is possible to estimate brain metabolic rate from the size of the arteries that supply the brain with blood," said lead author Roger Seymour in the School of Biological Sciences, University of Adelaide.

Researchers showed that the connection between intelligence and hole size stems from brain activity being related to brain metabolic rate. "During the course of primate evolution, body size increased from small, tree-dwelling animals, through larger monkeys and finally the largest apes and humans," Seymour said.

A human brain contains nearly 100 billion nerve cells with connections measured in the trillions. Each cell and connection uses a minute amount of energy but, added together, the whole brain uses about 20 per cent of a person's resting metabolic rate. If an artery passes through a bone, then simply measuring the size of the hole can indicate the blood flow rate and in turn the metabolic rate of the organ inside.

The blood flow rate and presumably brain metabolic rate increased with brain volume much faster than expected for mammals in general. By the time of the great apes, blood flow was about 280 per cent higher than expected.