Eating meat may have allowed our ancestors to grow fruitful, multiply and spread across the planet, a new study suggests. That's because carnivorous diets go hand in hand with early weaning, a behavioral trait that distinguishes humans from their closest ape cousins. The research appears in the latest issue of PLoS One.

The faster mothers wean their young, the sooner they can once again become pregnant, said lead author Elia Psouin of Lund University in Sweden. "Lactation and suckling are known to inhibit ovulation," she said. As a result, in species that practice early weaning, more offspring can be born to each female.

But why does a meat-heavy diet allow babies to become independent eaters at a young age? Psouni said the jury is still out on this question but suggested that two forces could be at work. First, carnivorous mothers might produce higher-quality breastmilk, giving their babies all the necessary nutrients for a healthy childhood faster and more efficiently. Second, it's possible that meat-eating young start digesting solid food earlier than their herbivore and omnivore counterparts.

Whatever the reason, the ancestors of modern humans acquired a major evolutionary advantage when they started consuming flesh between 2.6 and 2 million years ago, the researchers believe. As the interval between births narrowed, women began having more children during their lifetimes. The ensuing population explosion drove early humans to settle distant corners of the globe.

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