Brahui and Oraon: Tracing the Northern Dravidian genetic link back to Balochistan

The genetic origin of ethnic groups present in South Asia is complex. Widespread factors such as complex societal caste structure, language shifts, the coexistence of tribal alongside caste populations, and a varied and vast geography augment this complexity. In the face of this complexity, a holistic approach is required for the study of population histories. The isolated Dravidian population, Brahui in Pakistan, represents a remnant of complex ethnolinguistic population history. Genetic studies conducted to date have not demonstrated a close genetic link between the Brahui and other Dravidian populations of the Indian subcontinent. However, none of these studies included the Kurukh-Malto populations, which are linguistically closest to the Brahui. In this study, we included the Kurukh speaking Oraon population and their neighbours in high-resolution genetic analyses to investigate their allele and haplotype sharing with the Brahui population of Pakistan. Our intrapopulation analyses on Oraon collected from Bangladesh and India suggested a common South Asian source for the Oraon that is genetically distinct from the extent of Indian Mundari (Austroasiatic) populations. The interpopulation comparison of Oraon showed a closer genetic affinity with the geographically more distant Mawasi (North Munda) and Gond (South Dravidian) populations, rather than their immediate neighbours. Moreover, our extensive statistical analyses found no signal of an Oraon-related ancestry in Brahui. One possible explanation to this finding is that the genetic signature related to the Dravidian populations might have been entirely lost in Brahui due to extensive admixture with neighboring populations.