between South Asians and the native Andamanese (who are sometimes classified as Australo-Melanesians), stating that "The distinctiveness of Andamanese and southern Indian crania need not challenge the finding by Reich et al. for an "Ancestral South Indian" ancestry shared by southern Indians and Andamanese", and that the differences may be in part due to the greater craniometric specialization of South Asians compared to Andamanese. Genetics Groups ancestral to the modern Veddas were probably the earliest inhabitants of Sri Lanka. Their arrival is dated tentatively to about 40,000–35,000 years ago. They show a relationship with other South Asian and Sri Lankan populations, but are genetically distinguishable from the other peoples of Sri Lanka, and show a high degree of intra-group diversity. This is consistent with a long history of existing as small subgroups undergoing significant genetic drift. In one study on maternal (mitochondrial DNA) haplogroups in Sri Lankan populations (the Vedda, Sri Lankan Tamil, and Sinhalese), the Vedda were found to carry predominantly haplogroups U and R and to carry maternal haplogroup M at about 17%, unlike the Tamil people and many mainland Indian tribal groups, among which haplogroup M is predominant. The Vedda people and Low-country Sinhalese showed frequencies of haplogroup R at 45.33 and 25%, respectively. The Vedda were found to be distinct but closer to Sinhalese than to other South Asian groups . It was determined in the study to be likely that the branches of haplogroups R and U "found to be particularly prevalent in the Vedda, were derived from ancestors on the Indian subcontinent." Another study on maternal haplogroups in Sri Lankan groups (also the Vedda, Sri Lankan Tamil, and Sinhalese) found similar results, with the Vedda belonging predominantly to the mitochondrial haplogroup N (which "exists in almost all European, Oceanian, and many Asian and Amerindian populations.") and its subgroups U and R (with those comprising about two thirds of their maternal lineages), differing from other South Asian groups (such as the Sri Lankan Tamil, Sinhalese, and several Indian Tribal groups) among whom haplogroup M is predominant. The study also found that "South Asian (Indian) haplogroups were predominant" in the three Sri Lankan groups (including the Vedda) but that the Sinhalese, Sri Lankan Tamil, and Vedda populations also "had a considerable presence of West Eurasian haplogroups." One phylogenetic study on mitochondrial DNA hypervariable segments HVI and part of HVII showed the Vedda to be "genetically distinct