As the glaciers left Wisconsin the climate began to change. The temperature became warmer. The mammoths and mastodons became extinct. Some archaeologists think they became extinct because hunters killed too many. Other archaeologists think the warming climate caused the animals to die off. Right now we don't know which answer is correct; the answer might be a combination of both factors. Whatever the cause, the changing climate and the lack of large animals meant that people needed to adapt their ways of living.