Did humans trade guts for brains?

Humans are remarkably fuel-efficient, or at least, our brains are. The lump of tissue inside our skulls is three times larger than that of a chimp, and it needs a lot more energy to run. But for our size, we burn about as much energy as a chimp. We’re no gas-guzzlers, so how did we compensate for the high energy demands of our brains? In 1995, Leslie Aiello and Peter Wheeler proposed an answer – we sacrificed guts for smarts. The duo suggested that during our evolution, there was a trade-off between the sizes of two energetically expensive organs: our guts and our brain. We moved towards a more energy-rich diet of meat and tubers, and we took a lot of the digestive work away from our bowels by cooking our food before eating it. Our guts can afford to be much smaller than expected for a mammal of our ...