The first humans may have been beach-dwellers foraging for shellfish, not grassland hunter-gatherers, says a U of T scientist.
An international group of researchers including Stephen Cunnane, a professor in U of T's department of nutritional sciences, has assembled evidence that the large brains of the earliest humans could only have evolved on the nutrient-rich diet provided by shellfish and other animal life found near shorelines. "You don't need a big brain to collect mussels and clams. But living on them gives you the excess energy and nutrients that can then be directed towards brain growth."
The popular image of the earliest humans living on the African savanna must be wrong, Cunnane says. His team has found that a specific fatty acid, DHA, necessary for human brain and eye development, is easily available in food near shore environments but not in the diet of savanna mammals. This suggests humans evolved near water before spreading inland, he says.
"We'd like to see early humans as hunters who took advantage of nature and grew a big brain in the process," he says. "But how could that hunting ability miraculously appear overnight? Well, it didn't. Instead, they evolved in a place where they didn't have to hunt."
Cunnane believes recent hominid finds in South Africa that show proto-human fossils in close association with the remains of aquatic creatures are more evidence for the theory, which he hopes to further test next year by isotopic analysis of early human fossils.