Brain Size and Fitness

An interesting data point taken from E.O. Wilson’s The Social Conquest of Earth: bigger brains mean better adaptation to new environments. That seems trivial in a way because it is part of the “folk” evolutionary theory that seems to flow naturally from the assumption of human uniqueness and our ostensive position at the apex of the evolutionary mountain.

But it doesn’t have to be that way. A very narrowly adapted organism could conceivably outcompete an intelligent generalist. The generalist requires massive physiological commitments to the energetic requirements of behavioral plasticity. The specialist is economical, efficient. So it has largely been an article of projective faith in folk theory that the human condition is explainable.

So it is always refreshing when I learn that there is empirical evidence that brings clarity to issues like this:

Big brains are hypothesized to enhance survival of animals by facilitating flexible cognitive responses that buffer individuals against environmental stresses. Although this theory receives partial support from the finding that brain size limits the capacity of animals to behaviourally respond to environmental challenges, the hypothesis that large brains are associated with reduced mortality has never been empirically tested. Using extensive information on avian adult mortality from natural populations, we show here that species with larger brains, relative to their body size, experience lower mortality than species with smaller brains, supporting the general importance of the cognitive buffer hypothesis in the evolution of large brains.

From Sol et. al., Big-brained birds survive better in nature. The emphasis in the title on “nature” suggests that perhaps they fail in captivity? Avian ennui?

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