The study of human antiquities, especially of prehistoric period is known as archaeology. The biological and cultural evolution of man proceeded side by side and the two influenced each other. Like the physical remains of man, his cultural remains also lie buried in the ancient deposits. Often, the two categories of evidence are found together in the same layers of the rock. With the passage of time, and the increasing capacity of his brain and development in other bodily organs, man's culture became more and more varied and complex. He learnt the use of new materials for making tools and developed new techniques for improving them. The use of tools had a tremendous impact on increased access to food and therefore on cooperative living in colonies. In many areas, archaeological remains show reindeer to be the principal source of meat they ate.