Zen recently wrote mentioned this study on his blog, so I thought it was time to dredge it out of the archives. Also, I’ve just returned from APS (see my daily recaps here here and here), and I am TIRED.
Domestic animals and their wild counterparts can be different in big ways; there can be differences in morphology (physical characteristics), physiology, and behavior. These changes may depend on spontaneous adaptations to captivity or to artificial selection pressures arising from the motivation for domesticating the animal in the first place.
One change that is often observed as a result of domestication is a general reduction in relative brain size. This reduction has been observed in all species that have been investigated with only one exception: the house mouse (mus musculus). Importantly, this reduction is not simply a result of increased body size. Despite the fact that it has not been scientifically explored, many assume that the reductions in brain size are reflected in a similar reduction in brain function. In other words: smaller brains (relative to body size) and dumber animals.
Behold the domesticated guinea pig (Cavia aperea f. porcellus):
Figure 1: Guinea Pig. I don’t think they look much like pigs at all. Also, they are most definitely not from Guinea.