Comparative-quantitative investigations on brains of feral pigs from the Galapagos Islands and of European domestic pigs

Summary

An intraspecific allometric comparison between the brain weights of feral pigs from the Galapagos Islands and those of European domestic pigs shows identical brain sizes in relation to the body sizes. The return of domestic pigs to the wild life state some generations ago has produced no increase in brain size. Hence this process is not reversible to the process of domestication, domestic pigs having 33% smaller brains than free living mutuals of their ancestral species the European wild boar (Sus scrofa scrofa L.).

However, quantitative investigation shows a partly different composition of the brains of feral pigs compared with those of European domestic pigs. Of the fundamental brain parts, telencephalon and mesencephalon of the feral pigs are not different in volume size, whereas diencephalon and medulla oblongata are 6.5% and 10% larger, respectively; the cerebellum on the contrary is about 11% smaller than in domestic pigs. A further subdivision of the telencephalon into the regions of neocortex, corpus striatum and allocortex, and that of the allocortex into some olfactory and limbic centers, elucidates other differences. A discussion of these results under functional aspects and in connection with the process of return to wild-life conditions is given.