A people who appeared in northern Mesopotamia and Syria at the end of the 3rd millennium BC and by c 1600 BC had established a number of kingdoms in the area. They may have come from the Caucasus or Armenia and some evidence suggests a connection with the Kura-Araxes culture. They had a pantheon, distinct from that of their neighbors, which was recorded in the rock sanctuary of Yazilikaya by the Hittites. Their language - non-Semitic and non-Sumerian - is known from a number of religious texts and a letter among the archives of Tell el-Amarna. It is not related to any of the major language families. They came into contact with the Hittites, Assyrians, and Egyptians in the second half of the 2nd millennium BC. The Syrian part of their territory was absorbed into the Assyrian empire, but the district of Urartu remained independent until much later. The name Mitanni has come to be applied to an Indo-Iranian element in the population, which was aristocratic and probably responsible for introduction of horse and chariot into Near East. The language is not related to any known linguistic group, but close to Urartu (Armenian). It is an agglutinative language, with a series of suffixes being added to nouns and verbs to expression grammatical inflections.