Why Pets Have Surprisingly Small Brains

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When we domesticate an animal species, their brains shrink and they freak out less.

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To learn more, start your googling with these keywords:
Domesticated animal: a species of animal bred by humans over generations to become nonreactive and gain characteristics suitable for life as a farm animal or pet

Tame animal: an individual animal raised in a way that it has become less dangerous and frightened of people

Feral animal: an animal that escapes from captivity or domestication (& regains some similar & some different characteristics compared to its pre-domesticated state)

“Fight or flight”: an instinctive physiological response to a threatening situation that readies a creature to either to resist forcibly or escape

Limbic system: the brain’s “panic button” – a system of nerves and networks near the bottom of the cortex that controls basic emotions (e.g. fear, pleasure, anger) and drives (e.g. hunger, sex, dominance)

Telencephalon: the most developed and anterior part of the forebrain, consisting chiefly of the cerebral hemispheres, and the brain region that shrinks most in domesticated animals

Domestication: a sustained multigenerational, mutualistic relationship in which one species (e.g. humans) assumes a significant degree of influence over the reproduction and care of another species (e.g. cows) in order to secure a more predictable supply of a resource of interest (e.g. milk/meat/traction), and through which the domesticated organisms gain advantage over individuals that remain outside this relationship (e.g. aurochs, which went extinct), thereby benefitting and often increasing the fitness of both species involved

If you liked this week’s video, you might also like:

Brain Scoop video on brain size and intelligence:

Russian Fox Domestication Experiment:

What happens to domesticated animals & their brains when they escape back to the wild?:

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Credits (and Twitter handles):
Script Writer: Alex Reich (@alexhreich)
Script Editor: Emily Elert (@eelert)
Video Illustrator: Keenan Parry & Ever Salazar (@unpuntocircular)
Video Director: Emily Elert (@eelert)
Video Narrator: Emily Elert (@eelert)
With Contributions From: Henry Reich, Kate Yoshida, Ever Salazar, Peter Reich, David Goldenberg
Music by: Nathaniel Schroeder:



Agnvall, B. et al. 2017. Is evolution of domestication driven by tameness? A selective review with focus on chickens. Applied Animal Behaviour Science.

Eberhard, W. G., & Wcislo, W. T. 2011. Grade changes in brain-body allometry: morphological and behavioural correlates of brain size in miniature spiders, insects and other invertebrates. Advances in Insect Physiology, 40, 155.

Kruska, D. C. 2005. On the evolutionary significance of encephalization in some eutherian mammals: effects of adaptive radiation, domestication, and feralization. Brain, behavior and evolution, 65(2), 73-108.

Kruska, D. C. Personal Communication, Oct 2017.

Marchetti, M. P., & Nevitt, G. A. 2003. Effects of hatchery rearing on brain structures of rainbow trout, Oncorhynchus mykiss. Environmental biology of Fishes, 66(1), 9-14.

Marchetti, M. Personal Communication, Oct 2017.

Wright, D. Personal Communication, Oct 2017.

Zeder, M. A. 2012. Pathways to animal domestication. Biodiversity in agriculture: Domestication, evolution and sustainability, 227-259.

Zeder, M. A. 2015. Core questions in domestication research. Proceedings of the National Academy of Sciences, 112(11), 3191-3198.

Zeder, M. A. Personal Communication, Oct 2017.

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