Michael Witzel suggests an underlying, prefixing language that is similar to Austroasiatic, notably Khasi; he argues that the Rigveda shows signs of this hypothetical Harappan influence in the earliest historic level, and Dravidian only in later levels, suggesting that speakers of Austroasiatic were the original inhabitants of Punjab and that the Indo-Aryans encountered speakers of Dravidian only in later times.