Researchers looked at metabolite evolution in humans and found they progressed much more rapidly in the brain and muscles.
Metabolites are "small molecules like sugars, vitamins, amino acids and neurotransmitters that represent key elements of our physiological functions," a PLOS news release reported.
Only a few genomes that developed over time could be responsible for a number of "distinct human features," the news release reported.
A research team decided to look beyond the human genome and see what other types of molecules were responsible for human development.
For the first time the researchers looked at the evolution of the metabolome, which is the compendium of metabolites present in human tissues.
"Metabolites are more dynamic than the genome and they can give us more information about what makes us human," Doctor Philipp Khaitovich said in the news release. "It is also commonly known that the human brain consumes way more energy than the brains of other species; we were curious to see which metabolic processes this involves."
Unlike the "uniform pace" of the genome, the metabolome of the human brain evolved four times faster in humans than it did in chimpanzees; human muscles acquired metabolic changes at a rate 10 times faster than these primates.
In order to eliminate the idea that this is related to humans' sedentary lifestyles, the researchers put monkeys in a small enclosure and fed them foods high in sugar and fat. This lifestyle change proved to only have a small effect on muscle metabolome.
"For a long time we were confused by metabolic changes in human muscle," Doctor Kasia Bozek, the lead author of the study, said in the news release. "Until we realized that what other primates have in common, in contrast to humans, is their enormous muscle strength."
The study could suggest that the "metabolic roles of human brain and brawn are intertwined," the news release reported.
"The world of human metabolomics is just starting to open up its secrets to us," Doctor Patrick Giavalisco, who led the metabolome measurement effort at the Max Planck Institute for Molecular Plant Physiology in Golm, said in the news release. "Such human-specific metabolic features we find could be related not only to physical or cognitive performance but also to common human metabolic diseases."
