While only several thousand people wandered in the territory of Lithuania during the Stone Age, over time, demographics rapidly improved, and in the Iron Age there were already tens of thousands of people. Not surprisingly, they began to gather into distinct residential territories and ethno-cultural areas, separated by natural barriers such as woods, swamps, rivers and wastelands. Over the centuries, they developed specific customs, clothing styles and accessories—and their relation to warfare, trade and crafts differed somewhat. Today, they are known as nine ancient Baltic tribes, on the basis of which the first Lithuanian state was built in the 13th century—when, according to estimates, the number of inhabitants in Lithuanian territory might have reached several hundred thousand.