How can an archaeologist tell the difference between the bones of wild animals compared to domesticated animals?

There are differences between the bones of domesticated animal species and their wild ancestors, so depending on how much is preserved it is possible to work out if an animal was domesticated. As a general rule domesticated animals have been changed by humans through selective breeding to have characteristics which suit human needs. Domesticated animals used for food are often much larger in terms of the meat they have on them, but may be bred to be more managable - Cattle may be bred without horns, or pigs may have shorter legs. Animals kept for companionship often have physiological changes to make their skulls "cuter" or more human like.