Muscles Evolved More than the Brain

Evolution has made the human race smarter, but it might also have made us weaker. A new study revealed that humans evolved small muscles faster than they grew big brains, but over time we sacrificed muscle for brain energy.

Published Tuesday in the journal PLoS Biology, researchers studied how our brains and other organs have evolved over time compared most notably to our distant cousin, the chimp. Researchers from Shanghai’s CAS-MPG Partner Institute for Computational Biology conducted a study that found metabolites—small molecules of sugar, vitamins, amino acids, and neurotransmitters that represent significant elements of our physiological functions—accumulated faster in both human brains and muscles throughout evolution.

Researchers analyzed approximately 10,000 different metabolites in four species: humans (that included students and professors), chimpanzees, macaques, and mice.

The study showed that the human brain evolved four times faster than the chimp brain, and the human muscle changed over eight times compared to the chimp muscles.

However, the study suggests that human biology traded off muscle energy for brain energy, which increased our cognitive ability. Chimps on the other hand, developed stronger muscles, but weaker brains.

“For a long time we were confused by metabolic changes in human muscle, until we realized that what other primates have in common, in contrast to humans, is their enormous muscle strength,” Dr. Kasia Bozek, the lead author of the study, stated in a news release.

In a strength test between chimps and macaques and humans, which included students and athlete professionals, researchers found that our primate counterparts pulled higher results two times that of us humans.

“Our results suggest a special energy management in humans, that allows us to spare energy for our extraordinary cognitive powers at a cost of weak muscle,” Dr. Bozek stated.

These findings will not only lead to more research about evolution, but could also help developing cures for metabolic diseases.

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