Paleoindians (13,000 BC to 7,900 BC)
Archaeologists theorize that man first reached the Americas about 12,000 BC, via what is called the "Bering land bridge." This date marks the end of the Ice Age, or Pleistocene era, when much of the northern hemisphere was covered by huge glaciers. So much water was required to form the ice in these glaciers that the oceans were was 400 feet lower than they are now. This lower sea level turned much of what is now the Bering Sea into dry land. It is believed that Asian people crossed from Siberia to Alaska over this "land bridge" between the continents. Evidence of these Paleoindians, as archaeologists call them, are found scattered all over North America. It is not at all clear exactly when or how many migrations there were, or how they spread out over the continent. In fact, some archaeologists believe that man may have arrived in the Americas as early as 30,000 to 50,000 years ago.
We do know that the Paleoindians were experts at making stone spear points. They did not have bows and arrows, but used spears, or lances that were probably thrown and thrust at large animals. The earliest spear points are known as Clovis points, because they were first described from specimens found near Clovis, New Mexico. Several other related cultures from about this same period have also been identified, primarily on the basis of their stone spear points. It should be noted that most stone tools from North American archaeological sites are made of flint. Flint is a very hard rock that when chipped produces a curved fracture with extremely sharp edges. These edges are so sharp that one archaeologist actually had surgery performed with flint scalpels that he had fashioned for the surgeon.
The Paleoindians are believed to have hunted the now-extinct mega-mammals - elephants (mastodons and mammoths), wild horses, ground sloths, camels, and giant bison that roamed over North America. These large cold-climate herbivores were left from the Pleistocene era. The people that made the Clovis points probably stayed continually on the move, following their prey. As a result, they probably used only small widely scattered camps, and few durable items remain other than their spear points. Archaeological sites from this period are generally either camp sites with burnt bone and broken tools, or kill sites. The kill sites were often located at the bottom of cliffs, where the animals were stampeded of the cliff, or in places like "box canyons" where the herds could be trapped and slaughtered.
The maximum southern extent of the Pleistocene glaciers was approximately the present position of the Ohio and Missouri Rivers. However, the most recent advance, known as the Wisconsin Stage, only came as far south as central Ohio, Indiana, Illinois, and Iowa. South of the glaciers, the land was treeless tundra, similar to parts of the present day Canadian and Alaskan Arctic. Further south, along what is now Gulf Coast, the climate was sub-Arctic with spruce, fir, alder, and willow forests. By the time the Paleoindians arrived in North America the glaciers were retreating and covered most of Canada and only parts of the northern United States. The Paleoindians were well adapted to these cold climates, and were expert hunters. It is believed that their hunting skills may have caused the extinction of the mega- mammals at about the end of the Paleoindian period 8,000 BC. As they followed the trail of these animals they probably also foraged for herbs, nuts, and berries. Their survival was probably in many ways similar to modern Eskimos.