main idea. A. Judging from campsite remains, the first wave of immigrants to North America carried with them hunting tools they had successfully used to hunt large animals in Asia. B. Fossil bones suggest that several species of the long-horned bison once existed in North America, but by the time humans arrived, most of them had become extinct. C. The size of the bison's horns suggest that individuals lived alone or in small groups, a habit that made them attractive prey for human hunters. D. The bison began living in herds, which would have provided protection from hunters but also decreased the amount of food available for each individual. E. Early Americans preferred hunting long-horned bison for their horns which could be used to create sharp spear tips for hunting other large animals such as moose and musk ox. F. When bison began to live close together, this led to other adaptations in size and shape necessary for survival.