Dravidian is the name given to a linguistically related group of people in India. They are said to be the first original settlers of ancient India. Dravidian culture is very diverse, with some groups maintaining more traditional customs such as totemism and matralinealism, while others have developed the lifestyles of a modern technological society. Dravidian language has remained relatively intact despite a considerable amount of contact and intermarriage with other people in the Indian subcontinent. Today with more than one hundred seventy million speakers, the Dravidians make up the fourth largest linguistic group in the world. It is often presumed that Dravidians were the creators of the Indus River Valley Civilization and that they were occupying all of the Indian subcontinent when the Indo-Aryans invaded from Afghanistan (ca2000 BCE). The Dravidians were probably subjected by the Indo-Aryans and are the dasus of Vedic scriptures. Other Dravidians remained in a tribal state in central and southern India. Dravidians in general were gradually Hinduized, but retained their languages. The Tamil language is the first of the Dravidian languages to reflect the influence of Hinduism.