Did humans swap brains for brawn?

Why humans are far more intelligent than their closest living relatives like monkeys and apes may be because our ancestors swapped brains for brawn, a study has suggested.

"For a long time we were confused by metabolic changes in human muscles, until we realised that what other primates have in common, in contrast to humans, is their enormous muscle strength," explained Katarzyna Bozek from Chinese Academy of Sciences.

While the brain consumes a whopping 20 percent of the body's total energy, metabolic changes in human muscles were paralleled by a drastic reduction in muscle strength.

To gain insights into how the human brain evolved, scientists compared the metabolisms of humans and animals such as chimpanzees, mice and rhesus monkeys.

They focused on how much energy each species devoted to the brain and body.

They discovered that the rate of change in the metabolism of the human prefrontal cortex was about four times faster than that of chimpanzees, and the rate of change in the metabolism of human muscles was more than eight times faster than that of the chimpanzee, Live Science reported.

"Even after so many years of research of humans and human evolution, we still can uncover large unknown differences between humans and other species," Philipp Khaitovich, an evolutionary biologist at Chinese Academy of Sciences, added.

The study appeared in the journal PLOS Biology.