Mothers hard work linked to better brain growth in babies
Researchers at the Durham University who studied 128 mammals, including humans, found that the growth of brain in babies is determined by the length of the pregnancy and how long they are breastfed.
The findings, published in the journal "Proceedings of the National Academy of Sciences", add further weight to the WHO suggestion of six months` exclusive breastfeeding followed by continuing breastfeeding up to the age of two, the researchers said.
The study explains why humans, who suckle their babies for up to three years in addition to their nine-month pregnancies, have such a long period of dependency as this is necessary to support the growth of our enormous 1300cc brains, they said.
In comparison, species like fallow deer, which are about the same body weight as humans but remain in mothers` womb for seven months and get breastfed for six months, have brains six times smaller than that of the humans`, they added.
For their study, the Durham team analysed statisticalevidence on brain and body size, maternal investment, and life history variables in mammals, including species such as gorillas, elephants and whales.
They found 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. The study showed that length of the pregnancy determines brain size at birth and the period of lactation decides brain growth after birth. It also showed that mothers with higher metabolic rates can afford to fuel faster brain growth in the foetus.
Lead researcher Professor Robert Barton from Durham University`s Department of Anthropology said: "We already know that large-brained species develop slowly, mature later and have longer lifespans but what has not always been clear is why brains and life histories are related.
"One theory is that large brains increase lifespan by making the animal more generally flexible in its behavioural responses to unpredictable challenges, permitting slower life histories.
"However, our findings suggest that the slow-down in life histories is directly related to the costs rather than the benefits of growing a large brain."
The necessary benefits to offset these costs could come in other ways, such as improving specific cognitive abilities, rather than through some generalised flexibility, he said.
"Our findings help us to understand what the implicationsare 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," Dr Barton added.