Evolution has not only made human brains larger but has also increased the supply of blood to the brain, a study revealed. The research team calculated how blood flowing to the brain of human ancestors have changed over the time – using the size of two holes at the base of the skull at allow arteries to pass to the brain. The findings – published in the Royal Society journal Open Science – allowed the researchers to track the increase in human intelligence across evolutionary time. “Brain size has increased about 350% over human evolution but we have found that blood flow to the brain has also increased an amazing 600%,” said Australia’s University of Adelaide Professor Roger Seymour. “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,” he said. To allow our brain to be o intelligent, it must be constantly fed oxygen and nutrients from the blood. The metabolically active brain requires more blood so the supply arteries are larger and the holes in fossil skulls are accurate gauges of arterial size. “The size of ancient fossil skull holes show how blood flow has increased from three million-year-old Australopithecus to modern humans,” said South Africa’s University of the Witwatersrand Researcher Edward Snelling. “The intensity of brain activity was – before now – believed to have been taken to the grave with our ancestors,” he said.