The model shows that the young of all species cease to suckle when their brains have reached a particular stage of development on the path from conception to full brain-size. Carnivores, due to their high quality diet, can wean earlier than herbivores and omnivores.
The model also shows that humans do not differ from other carnivores with respect to timing of weaning. All carnivorous species, from small animals such as ferrets and raccoons to large ones like panthers, killer whales and humans, have a relatively short breast-feeding period. The difference between us and the great apes, which has puzzled previous researchers, seems to depend merely on the fact that as a species we are carnivores, whereas gorillas, orangutans and chimpanzees are herbivores or omnivores.
A few years ago, the Lund group published an acclaimed study on the point at which the young of various animals start to walk. Here too, similar patterns were discovered between mammalian species that diverged in evolution millions of years ago. A particular stage in brain development seems quite simply to be the time to start to walk, independently of whether you are a hedgehog, a ferret or a human being.
"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. Social and cultural factors surely influence the variation between humans", says Elia Psouni.
She is careful to emphasise that their results concern human evolution. The research is about how carnivory can have contributed to the human species' spreading on earth and says nothing about what we should or should not eat today in order to have a good diet.