THE ROLE OF UNCONSCIOUS SELECTION IN THE DOMESTICATION OF SHEEP AND GOATS

It is proposed that many of the morphological, physiological and behav ioural traits that characterize domestic sheep and goats and distingui sh them from their wild ancestors (e.g. diminished sexual dimorphism; diminution in brain, body and horn size and changes in shape of the ho rns; changes in pelage coloration) were shaped, to a large extent, by unconscious selection. It is argued that once founder herds had been a ssembled and controlled by humans, the very transfer of these animals from their wild environments into the widely different human-made husb andry system caused automatically drastic changes in selection pressur es. Several adaptations, vital for survival in the wild, lost their fi tness under the new conditions and broke down. New traits (which chara cterize domestic caprines) were promptly and unconsciously selected fo r. Protection from predators, culling of young males, protection from the elements, and changes in land use and in food and water supplies a re considered the main ecological factors introduced by humans at the start of caprine domestication. We evaluate the shifts in the selectio n pressures brought about by each of these changes, and sketch their e xpected impact on the morphology, physiology and behaviour of the huma n-controlled herds. We also indicate which of the domestication traits (expected to be automatically selected for under the new set of condi tions) are detectable in animal remains recovered from archaeological excavations.