The tamer the cow, the smaller the brain


By Michael Price, Science Magazine

Jun. 8, 2021


Compare a wild boar with a domestic pig and you may notice a few key differences, including the fact that the pig will likely have a smaller head—and brain—than the boar. Scientists have known for decades that domesticated animals like sheep, pigs, cats, and dogs have smaller brains than their wild counterparts—part of what scientists refer to as “domestication syndrome.” Now, the first large-sale study of brain sizes across cattle breeds reveals a new wrinkle: Breeds that tolerate more interaction with humans have smaller brains than those that live more independent lives.


Cattle were first domesticated from bison-size animals called aurochs (Bos primigenius) in the Middle East about 10,000 years ago, part of a wave of livestock domestication that included pigs, sheep, and goats. To find out how the brains of aurochs—which went extinct some 400 years ago—compared with those of their domesticated descendants, paleontologist Ana Balcarcel of the University of Zurich and colleagues used computerized tomography to scan 13 auroch skulls from museum collections across Europe. Next, they scanned the skulls of 317 cows and bulls, also from museum collections, representing 71 different breeds from around the world. They also measured the muzzle width of the skulls to estimate overall body size.


Then the researchers used their scans to calculate average brain size, relative to body size, for wild versus domestic cattle. Following the pattern of other animals that have undergone domestication, they found that the domesticated animals had brains about 25% smaller than their wild forebears, the researchers report today in the Proceedings of the Royal Society B.


With the data in front of her, Balcarcel realized...