Carnivorous humans

Vegetarianism was not part of human evolution:

A taste for meat prompted early humans to wean their children at a young age. The idea explains why we now wean our infants years earlier than other great apes.

In non-industrialised societies, women breastfeed their children for an average of two and a half years, while chimpanzees feed theirs for five. Anthropologist Gail Kennedy of the University of California, Los Angeles, US, suggests that humans made the transition to early weaning 2.6 million years ago.

That was when a branch of hominids began to eat animal carcasses - a risky activity that would have brought them into contact with other predators and significantly raised mortality rates for the hunters. This would have created a selection pressure to wean infants earlier and earlier, since those no longer dependent on breast milk would have been more likely to survive their mother's death, says Kennedy.

What is more, the nutritional benefit of eating meat at a younger age would have helped children's brains to grow and develop more quickly. Human brains grow three times quicker than those of chimpanzees.