Studies based on Mitochondrial DNA (mtDNA) variations have reported genetic unity across various South Asian sub–populations, showing that most of the ancestral nodes of the phylogenetic tree of all the mtDNA types originated in South Asia. Conclusions of studies based on Y Chromosome variation and Autosomal DNA variation have been varied. Recent genome studies appear to show that most South Asians are descendants of two major ancestral components, one restricted to South Asia ("Ancestral South Indian", derived from West-EurasianIVC-people and a distinctive native South Asian population, which was distantly related to the Andamanese and East Asians), and the other component ("Ancestral North Indian," derived from West-Eurasian IVC-people and Pontic Steppe-pastoralists, making them closely related to those in Central Asia, West Asia and Europe. Basu et al. (2016) identified two more ancestral components in mainland India, denoted as "AAA" and "ATB", that are major for the Austro-Asiatic-speaking tribals and the Tibeto-Burman speakers respectively. The study also infers that the populations of the Andaman Islands archipelago form a distinct ancestry, which "was found to be coancestral to Oceanic populations" and distant from contemporary South Asians. Yelmen et al. 2019 concluded that the AASI (Ancient Ancestral South Indians) form their own ancestral clade, best represented by the indigenous tribes, such as the Irula people and Paniya people. The East Asian ancestry component detected in India is mainly restricted to specific populations in the Himalayan foothills and Northeast India.