Having a big brain can be great. Whipping your friends at trivial pursuit, acing every test you take, and flaunting your vast knowledge to the world. But what is the cost? Researchers recently reported in Current Biology on tests run on guppies

photo credits to iosonoadry

and discovered some evolutionary setbacks to large-brained guppies.

Through tests with large-brained and small-brained guppies, the scientists determined that a large brain can have adverse effects on gut size and reproductive output.

The reason behind this, and the reason why this is important for humans as well, is because of the amount of mass the brain has versus the amount of energy it requires. In humans, the brain accounts for only 2 percent of the total body mass but makes up 20 percent of the energy requirement of the body. As Niclas Kolm said  “It is a remarkably costly organ energetically.” The idea is that there is a tradeoff between the brain and other organs, and as the brain gets bigger and requires more energy, the other organs must get smaller.

The group’s research suggest that humans and primates, animals with large brains, have relatively small family size because of the tradeoff between brain size and reproduction ability.