As Big Game Hunters they probably lived as a number of families attached to a herd and relatively independent of each other except at hunting times. They had no homes, only temporary camps, and were bound to a moving herd, not to any particular region. The Paleo-Indian culture consisted of methods of trapping and slaying the great beasts and of filling other simple physical needs; a simple code of social behavior which enabled men and wives to live together with their children and, for brief periods, in gatherings of the families in relative peace and contentment; with religious beliefs and rites suitable to their cultural level that they believed assured them of a continuance of their satisfactory existence. When the climate changed, those families that chose to remain in Illinois had to develop, perhaps slowly and painfully, a new way of life. The habits and haunts of deer, elk, bear and raccoon had to be learned. Other methods of hunting and of making tools and devices to fit new conditions were invented as a result of the new fund of knowledge assembled. Each family eventually acquired a more or less definite piece of land or hunting territory in which it selected certain favorable places to build the temporary hamlet at suitable seasons. As the man and his family became better adapted to the land and its resources, he hunted more successfully, and the family or local group grew larger in number. Probably a number of neighboring families, when food was especially abundant, gathered together for social and religious purposes as peoples living today in the same status still do. Religious beliefs and other customs had all this time doubtless been shifting gradually in meeting the needs and dangers of changing conditions to a new way of life we call the Archaic culture. Every way of life is built on an older, often simpler, culture from which it has changed more or less rapidly. Due to important inventions, the group may modify its economy (ways of securing and processing food, etc.) and produce a substantially improved manner of living which, from archaeological evidence alone, may be difficult to recognize as a development from its earlier phase. On occasion, people from another region may invade an area, drive out the inhabitants and bring in a differing way of life. Usually this merely extends, to a desirable region less effectively exploited by others, the range of a vigorous cultural group whose territory has become too densely populated. Sometimes newcomers essay to live peaceably with the natives and a new cultural blend is developed. If fundamental changes are made in the economy by internal development or by imitating another culture, social and religious customs are very likely to change too, though usually at a slower pace.