Scientists have long suspected that big brains come with an evolutionary price — but now they've published the first experimental evidence to support that suspicion, based on their efforts to breed big-brained fish.
A Swedish team found it relatively easy to select and interbreed common guppies to produce bigger (or smaller) brains — as much as 9.3 percent bigger, to be precise. But the bigger-brained fish also tended to have smaller guts and produce fewer babies.
This finding is consistent with what's known as the "expensive-tissue hypothesis" — the idea that there's a trade-off between the demands of the brain and the demands of other organs. For example, we humans have bigger brains than other primates, relative to body size. About 20 percent of the energy we take in is used up by the brain, which represents just 2 percent fo our body mass. But the amount of energy devoted to digestion is smaller, relatively speaking.
Read more at NBC News.
