Although this is a discussion I enter into with great hesitancy, I highly recommend Asko Parpola's recent work, The Roots of Hinduism, for those wishing to delve deeply into these issues. Parpola's remarkable synthesis of the archaeological record with millennia of cultural evidence anticipates Reich's DNA work -- as cited in the BBC article. However, Parpola's analysis focuses not on divisiveness (between Indus and Vedic, etc.) in Indian culture ... but rather on the fact that India today still reflects a cultural patrimony of great variety (likely drawn from genetic and cultural connections stretching from India to the steppes and to western Asia). This trend to see cultural continuity is not unknown in recent scholarship (Biardeau; Hiltebeitel, etc.); Parpola's work, however, carries it very far forward.
(By way of full disclosure; I recently reviewed Parpola's book.)
Herman Tull
Lafayette College