A new study has revealed that human children grow slowly, as compared to the closest animal relatives, because their brain requires huge amount of energy fuel.
The research led by Northwestern University anthropologists found that a five-year old's brain uses twice as much glucose (the energy that fuels the brain) as that of a full-grown adult. It showed that energy funneled to the brain dominates the human body's metabolism early in life and was likely the reason why humans grow at a pace more typical of a reptile than a mammal during childhood.
Christopher Kuzawa, professor of anthropology at Northwestern's Weinberg College of Arts and Sciences, said that human's body can't afford to grow faster during the toddler and childhood years because a huge quantity of resources was required to fuel the developing human brain and as people have so much to learn, so that learning requires a complex and energy-hungry brain.
At 4 years of age, when this "brain drain" would be at its peak and body growth slows to its minimum, the brain burns through resources at a rate equivalent to 66 percent of what the entire body uses at rest.
The mid-childhood peak in brain costs has to do with the fact that synapses, connections in the brain, max out at this age, when people learn so many of the things they need to know to be successful humans. At its peak in childhood, the brain burns through two-thirds of the calories the entire body uses at rest, much more than other primate species.
The study is published in the journal Proceedings of the National Academy of Sciences.
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