London: Meat eating helped early humans to spread more quickly across the world and had a profound effect on human evolution, scientists say.
Researchers from Lund University in Sweden found that the high-quality diet allowed mothers to wean babies earlier and have more children, allowing human communities to grow faster.
The researchers, who detailed their findings in the scientific journal PLoS ONE, compared 67 species of mammals, including humans, apes, mice and killer whales, and found a clear correlation between eating meat and earlier weaning.
They also found that babies of all species stop suckling when their brains have developed to a particular stage, but that carnivores reached this point more quickly than herbivores or omnivores.
"Eating meat enabled the breast-feeding periods and thereby the time between births to be shortened," lead study author Elia Psouni was quoted as saying by the Daily Mail.
"This must have had a crucial impact on human evolution."
Among natural fertility societies, the average duration of breast-feeding is two years and four months. This is not much in relation to the maximum lifespan of our species, around 120 years, the researchers said.
It is even less if compared to our closest relatives: female chimpanzees suckle their young for four to five years, whereas the maximum lifespan for chimpanzees is only 60 years.
Researchers in the past had tried to explain the relatively shorter breast-feeding period of humans based on social and behavioural theories of parenting and family size.
But, the Lund group has now shown that the young of all species stop suckling when their brains have reached a particular developmental stage.
The difference is that carnivores -- categorised as species for which at least 20 per cent of the energy content of their diet comes from meat -- reach this point earlier than herbivores or omnivores due to their higher quality diet, the researchers found.
Therefore, the different weaning times for humans and the great apes seems to result simply from the fact that, as a species, humans are carnivores, whereas gorillas, orangutans and chimpanzees are herbivores or omnivores, Dr Psouni said.
She said: "That humans seem to be so similar to other animals can of course be taken as provocative.
"We like to think that culture makes us different as a species.
"But when it comes to breast-feeding and weaning, no social or cultural explanations are needed; for our species as a whole it is a question of simple biology."
Dr Psouni was careful to emphasise that their results provide insight into how eating meat may have contributed to early humans spreading on Earth, and said nothing about what humans today should or should not eat.