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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: https://www.youtube.com/watch?v=hJW8jIDfP9E
Russian Fox Domestication Experiment: https://goo.gl/5nWnXz
What happens to domesticated animals & their brains when they escape back to the wild?: http://www.nature.com/news/when-chickens-go-wild-1.19195#/free%5C
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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. https://goo.gl/J86NEd
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. https://goo.gl/GL6LWG
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. https://goo.gl/2xWSB8
Zeder, M. A. 2015. Core questions in domestication research. Proceedings of the National Academy of Sciences, 112(11), 3191-3198. http://www.pnas.org/content/112/11/3191.full
Zeder, M. A. Personal Communication, Oct 2017.