It from the time of the Ice Age, or Pleistocene Epoch . The climate was much colder and it was a time of alternate expansions and retreats of the glaciers. During the time of the first people, the glaciers covered much of North America a as far south as what we know as Iowa, South Dakota, and Wisconsin. The first people were hunters of big game animals such as mammoth . By the time the glaciers retreated for the last time, many of these animals had become extinct.
Some archaeologists believe it was due to changing climate.
Others believe it was the result of overhunting by these first people. Whatever the case, on the Great Plains the mammoth had disappeared by about 8,000 years ago. Let's take a look at what scientists think about the first case of how climate caused culture to change on the northern Great Plains. The first people to live in North America were those who later became known as American Indians or Native Americans. Their own stories, told to generations, tell of how their peoples came to be.