Human muscle may be unique
It's pretty clear that when it comes to brains, humans are unique creatures. But a new study suggests that it also appears to be true of our muscles.
The research, published in PLOS Biology, looked at the evolution of metabolites, which are small molecules like sugars, vitamins, amino acids and neurotransmitters that are important to our physiological functions. Researchers found that metabolite concentrations rapidly evolved in two tissues during human evolution--in the brain and the muscle. Unlike the steady evolution of the genome, the human brain has evolved four times faster than that of the chimpanzee, but the human muscle changed 10 times faster than a chimpanzee's.
To ensure the change didn’t reflect a couch potato lifestyle adopted by humans, researchers did some tests on macaque monkeys. The monkeys were moved from a spacious countryside facility to a small indoor enclosure and served fatty and sugary food for a few weeks. These lifestyle changes hadd only a small effect on the muscle metabolome of the monkeys. In another test with macaque monkeys and chimpanzees, researchers analyzed their muscle strength compared to humans in a pulling strength competition. In all these tests, the primates won the strength tests by twofold over the humans.
This suggests that the metabolic role of the brain and muscles are intertwined and, the researchers suggested, that perhaps the brain takes more energy for cognitive powers, which weakens the muscles.