The first people settled in the territory of Lithuania after the last glacial period in the 10th millennium BC: Kunda, Neman and Narva cultures. They were traveling hunters and did not form stable settlements. In the 8th millennium BC, the climate became much warmer, and forests developed. The inhabitants of what is now Lithuania then travelled less and engaged in local hunting, gathering and fresh-water fishing. Agriculture did not emerge until the 3rd millennium BC due to a harsh climate and terrain and a lack of suitable tools to cultivate the land. Crafts and trade also started to form at this time. Over a millennium, the Indo-Europeans, who arrived in the 3rd – 2nd millennium BC, mixed with the local population and formed various Baltic tribes.