Final answer:
The food bones from Choukoutien mainly came from deer, which were a significant source of food and provided materials for clothing.
Step-by-step explanation:
The majority of the food bones from Choukoutien, which is a site associated with prehistoric human activity, primarily came from the animal deer. While bison, antelope, and small animals like rabbits and birds were also part of the diet of plains peoples, deer remains a significant source of food and was commonly hunted for sustenance. Various plant foods such as seeds, berries, nuts, and tubers, supplemented this diet, but when it came to animal sources for food, deer provided not just the meat but also hides for clothing and other necessities.