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Fear in the Wild

The Evolution of Fear

All mammals, birds and even reptiles have amygdalae, or similar brain structures, which control the fear response. Evolution has preserved the structures that enable animals to experience fear because the emotion has served animals well, helping to protect them from danger, injury and death.

Black arrows in the brain slice images below point out an amygdala in each animal's brain. As is the case in humans, each of these animals has two amygdalae – one on either side of the brain. The picture at the bottom of the page is included to show the size of different animals' brains.

Horse brain slice

Cow brain slice

Dog brain slice

Pig brain slice


Animal specimens were donated and plastinated by the College of Veterinary Medicine at the University of Tennessee Knoxville. Please note: No animals were killed for this exhibit.