Anatolia were the Hattians in central Anatolia, and Hurrians further to the east. The Hattians were an indigenous people, whose main center was the city of Hattush. Affiliation of Hattian language remains unclear, while Hurrian language belongs to a distinctive family of Hurro-Urartian languages. All of those languages are extinct; relationships with indigenous languages of the Caucasus have been proposed, but are not generally accepted. The region became famous for exporting raw materials. Organized trade between Anatolia and Mesopotamia started to emerge during the period of the Akkadian Empire, and was continued and intensified during the period of the Old Assyrian Empire, between the 21st and the 18th centuries BCE. Assyrian traders were bringing tin and textiles in exchange for copper, silver or gold. Cuneiform records, dated circa 20th century BCE, found in Anatolia at the Assyrian colony of Kanesh, use an advanced system of trading computations and credit lines. Hittite Anatolia (18th–12th century BCE) Unlike the Akkadians and Assyrians, whose Anatolian trading posts were peripheral to their core lands in Mesopotamia, the Hittites were centered at Hattusa (modern Boğazkale) in north-central Anatolia by the 17th century BCE. They were speakers of an Indo-European language, the Hittite language, or nesili (the language of Nesa) in Hittite. The Hittites originated from local ancient cultures that grew in Anatolia, in addition to the arrival of Indo-European languages. Attested for the first time in the Assyrian tablets of Nesa around 2000 BCE, they conquered Hattusa in the 18th century BCE, imposing themselves over Hattian- and Hurrian-speaking populations. According to the widely accepted Kurgan theory on the Proto-Indo-European homeland, however, the Hittites (along with the other Indo-European ancient Anatolians) were themselves relatively recent immigrants to Anatolia from the north. However, they did not necessarily displace the population genetically; they assimilated into the former peoples' culture, preserving the Hittite language. The Hittites adopted the Mesopotamian cuneiform script. In the Late Bronze Age, Hittite New Kingdom () was founded, becoming an empire in the 14th century BCE after the conquest of Kizzuwatna in the south-east and the defeat of the Assuwa league in western Anatolia. The empire reached its height in the 13th century BCE, controlling much of Asia Minor, northwestern Syria, and northwest upper Mesopotamia. However, the Hittite advance toward the Black Sea coast was halted by the semi-nomadic pastoralist and tribal Kaskians, a non-Indo-European people who had earlier displaced the Palaic-speaking Indo-Europeans. Much of