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'Breastfeeding may lead to bigger brains in mammals'

Baby mandrill with its mother
Image caption Mammals which suckle their young for longer tend to have bigger brains researchers say

Brain growth in babies is linked to the amount of time and energy mothers invest, according to research carried out at Queen's University Belfast.

The researchers said the study of 128 mammal species, including humans, showed that brain growth in babies is determined by the duration of pregnancy and how long they suckle.

It concluded that the longer the pregnancy and breastfeeding period, the bigger a baby's brain would grow.

The results reinforce the idea that "breast is best" for developing brains, and backs up the World Health Organisation's advice that infants should be exclusively breastfed for at least six months.

The Durham University and Queen's University Belfast research, published in the Proceedings of the National Academy of Sciences, may help to explain why human infants have such a long period of dependency compared with some other mammals.

The scientists said this was necessary to support the growth of our brains, which are much larger than most animals as a proportion of body size.

For example fallow deer, which weigh about the same as humans, are only pregnant for seven months and suckle their young for about six months, have brains of only 220cc, six times smaller than the average adult human brain.

'Greater costs'

The research was based on statistical data related to brain and body size and maternal investment in mammals, including species such as gorillas, elephants and whales.

The researchers claimed their study showed that brain size relative to body size was most closely linked to maternal investment - the amount of time a mother spends carrying her offspring in pregnancy and how long she continues to breastfeed.

They also argued that the length of the pregnancy "determines brain size at birth and the period of lactation decides brain growth after birth".

Co-author of the investigation, Dr Isabella Capellini, from Queen's University, said the study showed that a slower pace of life and increased lifespan in species with larger brains, such as humans, were a consequence of the greater costs of growing large brains.

"These costs are certainly offset by some benefits, and our research suggests that these are more likely related to improvements in specific perceptual and cognitive abilities rather than a more general flexibility on behaviour and cognition as so far suggested," she said.

"Our findings help us to understand what the implications are of evolutionary changes at different stages, before and after birth, but we now need to do more research to pinpoint exactly how changes to the pre and postnatal growth phases affect the structure of the brain."

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