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A new international study that looks at how different species' bodies evolve over time has found that as humans have acquired more brain power, they have lost power in the brawn department. Researchers recently examined 10,000 different chemical compounds across 14 individuals of four different mammalian species. What they found in humans was surprising: the chemical composition of our muscle has changed at a faster rate historically than that of our brains. Indeed muscle and brain metabolism in humans has changed more in the last 6 million years than in the preceding 130 million years.

What's the Big Idea?

The brain's greediness for energy has forced other biological systems to economize, particularly muscle tissue. "Though they constitute only 2% of an adult’s body weight, they consume a fifth of his or her metabolic energy. Indeed, according to a school of thought led by Richard Wrangham of Harvard University, keeping the brain running is so demanding that only the invention of cooking, which makes more nutrients available from a given amount of food than can be extracted from it in its raw state, permitted the neurological expansion which created Homo sapiens."

Read more at the Economist

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