Brain size and intelligence not closely related in animals, study finds

bat body size changed far more than brain size/Valeriy Kirsanov, Fotolia

From “Evolution Mostly Driven by Brawn, Not Brains, Analysis Finds” (ScienceDaily, Oct. 15, 2012), we learn,

The most common measure of intelligence in animals, brain size relative to body size, may not be as dependent on evolutionary selection on the brain as previously thought, according to a new analysis by scientists.

Essentially, Max Planck Institute scientists found that the main pressure for adaptation falls on body size. Brain size may or may not follow:

For example, the evolutionary history of bats reveals they decreased body size much faster than brain size, leading to an increase in relative brain size. As a result, small bats were able to evolve improved flying maneuvrability while maintaining the brainpower to handle foraging in cluttered environments.

That does not mean that small bats are smarter than large bats. It just means that body size had to decrease but brain size did not.

We are also told,

For example, although the human brain is not the largest in the animal kingdom in terms of volume or mass, it is exceptionally large considering our moderate body mass.

comparative brain sizes in mammals/ Zoofari, Wikimedia Commons

Well, the human brain is different from animal brains by orders of magnitude, in terms of what it can do. Otherwise, I wouldn’t be writing this, and you wouldn’t be reading it.

A comparison of the human brain with, say, the brains of whales or elephants, is not useful. It merely confuses the issues around what drives brain size in animals. The need to situate humans firmly and only in the animal kingdom often produces these warps in discussion, which may impede research. Researchers spend an inordinate amount of time accounting for the human brain when they would be better advised not to, but simply ask: What factors usually guide the size of animal brains?