Humans grow slowly but it's all for a good cause

You may not think it, but compared to our closest animal relatives humans grow incredibly slowly – more like reptiles than mammals.

There’s a good reason for it though, and it concerns your brain. The brain of a five-year-old uses twice as much glucose (the energy responsible for fuelling the brain) as that of an adult, a study led by Northwestern University anthropologists has found.

“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,” said William Leonard, co-author of the study.

A state of the art MRI scanner in use at a children’s hospital in Liverpool (Bruce Adams/Daily Mail/PA)

Data from PET and MRI scans were pooled, for the first time ever in a study, to show that the brain is using the most resources at the ages where growth is slowest.

At age four, the brain consumes glucose at a rate comparable to more than 40% of the body’s total energy expenditure.

“As humans we have so much to learn, and that learning requires a complex and energy-hungry brain.” said Christopher Kuzawa, first author of the study and a professor of anthropology at Northwestern’s Weinberg College of Arts and Sciences.

The findings were published in the journal Proceedings of the National Academy of Sciences.