Anthropologist Richard Wrangham and his colleagues at the Harvard University in the US have found that tubers and the ability to cook them prompted the evolution of large brains, smaller teeth, modern limb proportions and the male-female bonding in humans. The observations challenge the current belief that eating meat spurred the evolution of Homo Erectus , the 1.8-million-year-old species that was the first to possess many human-like traits, say some anthropologists. But sceptics say that if early humans did cook tubers, then they must have controlled fire about 1.8 million years ago. But the first clear evidence of hearths dates back to only about 250,000 years ago ( Science , Vol 283, No 5410).