Mammals: Is It Better To Be Horny or Brainy?

A still from a YouTube video captures the classic predator-prey faceoff: the comparatively bigger-brained lion against a horned wildebeest. Credit: Wildlife Safari TV. The arms race between prey and predator has been around since the first time one microbe evaded another; it's a never-ending spiral of adaptations to be faster, stronger or better-defended. Now a new study looking at antipredator defenses across 647 species of mammals has found animals seem to have taken a couple different evolutionary paths to avoid being eaten. Each path came with a trade-off, however. According to the paper published today in Proceedings of the Royal Society B: Biological Sciences, mammals evolved antipredator defenses in one of two directions: bigger brains or brawnier armor, be it horns, quills, plating, stinky sprays or grenade launchers (okay, kidding on that last one). We've long known that brains are high-maintenance, or "metabolically expensive" in scientific parlance. That gray matter needs high-quality fuel and a lot of it to perform. Researchers have looked at numerous ways animals — including humans — have taken energy away from other needs to devote it towards building and maintaining ever-bigger brains. (Although, here's a fun fact: one of those "big brain" theories took a hit last week when a team announced they found no correlation between bigger brains and reduced tooth size in hominins, which we had long thought was the case. Hey folks, it happens. The advance of science is not a straight line, it's a zig-zag.) Until now, researchers hadn't really looked closely at whether some animals evolved a different strategy for survival: devoting more energy to physical defenses and less to bigger brains.