The Indo-Aryan migrations theory explains the common features shared by Sanskrit and other Indo-European languages by proposing that the original speakers of what became Sanskrit arrived in South Asia from a region of common origin, somewhere north-west of the Indus region, during the early 2nd millennium BCE. Evidence for such a theory includes the close relationship between the Indo-Iranian tongues and the Baltic and Slavic languages, vocabulary exchange with the non-Indo-European Uralic languages, and the nature of the attested Indo-European words for flora and fauna.