The term Negrito refers to several ethnic groups in isolated parts of Southeast Asia. Their current populations include the Aeta, Agta, Ayta, Ati, Dumagat and at least 25 other tribes of the Philippines, the Semang of the Malay peninsula, the Mani of Thailand and 12 Andamanese tribes of the Andaman Islands of India.
Negritos share some common physical features with African pygmy populations, including short stature and dark skin; however, their origin and the route of their migration to Asia is still a matter of great speculation. They are genetically distant from Africans and shown to have separated early from Asians, suggesting that they are either surviving descendants of settlers from an early migration out of Africa, or that they are descendants of one of the founder populations of modern humans.
Sometimes the term "Negroid" will be used when referring to these groups, especially to their superficial physical features, such as their hair and skin color.
According to James J.Y. Liu, a professor of comparative literature, the Chinese term Kun-lun means Negrito.
Being among the least-known of all living human groups, the origins of the Negrito people is a much debated topic. The Malay term for them is orang asli, or original people. They are likely descendants of the indigenous populations of the Sunda landmass and New Guinea, predating the Mongoloid peoples who later entered Southeast Asia. Alternatively, some scientists claim they are merely a group of Australo-Melanesians who have undergone island dwarfing over thousands of years, reducing their food intake in order to cope with limited resources and adapt to a tropical rainforest environment. Anthropologist Jared Diamond in his bestselling book, Guns, Germs, and Steel suggests that the Negritos are possible ancestors of the Aboriginal Australians and Papuans of New Guinea.
A number of features would seem to suggest a common origin for the Negritos and African pygmies, especially in the Andamanese Islanders who have been isolated from incoming waves of Asiatic and Indo-Aryan peoples. (No other living human population has experienced such long-lasting isolation from contact with other groups .) These features include short stature, very dark skin, woolly hair, scant body hair and occasional steatopygia. The claim that Andamanese pygmoids more closely resemble Africans than Asians in their cranial morphology in a 1973 study added some weight to this theory before genetic studies pointed to a closer relationship with Asians. Other more recent studies have shown closer craniometric affinities to Egyptians and Europeans than to Sub Saharan populations such as that of African Pygmies. Walter Neves' study of the Lagoa Santa people had the incidental correlation of showing Andamanese as classifying closer to Egyptians and Europeans than any Sub Saharan population. Multiple studies also show that Negritos from Southeast Asia to New Guinea share a closer cranial affinity with Australo-Melanesians. Further evidence for Asian ancestry is in craniometric markers such as sundadonty, shared by Asian and Negrito populations.
It has been suggested that the craniometric similarities to Asians could merely indicate a level of interbreeding between Negritos and later waves of people arriving from the Asian mainland. This hypothesis is not supported by genetic evidence that has shown the level of isolation populations such as the Andamanese have had. Some studies have suggested that each group should be considered separately however as the genetic evidence refutes the notion of a specific shared ancestry between the "Negrito" groups of the Andaman Islands, Malay Peninsula, and Philippines.
While earlier studies such as that of WW Howell allied Andamanese craniometrically with Africans they did not have recourse to genetic studies. Later genetic and craniometric (mentioned earlier) studies have found more genetic affinities with Asians and Polynesians. A study on blood groups and proteins in the 1950s suggested that the Andamanese were more closely related to Oceanic peoples than Africans. Genetic studies on Philippine Negritos, based on polymorphic blood enzymes and antigens, showed they were similar to surrounding Asian populations.
Genetic testing places all the Onge and all but two of the Great Andamanese in the mtDNA Haplogroup M, found in East Africa, East Asia, and South Asia, suggesting that the Negritos are at least partly descended from a migration originating in eastern Africa as much as 60,000 years ago. This migration is hypothesized to have followed a coastal route through India and into Southeast Asia. Analysis of mtDNA coding sites indicated that these Andamanese fall into a subgroup of M not previously identified in human populations in Africa and Asia; these findings suggest an early split from these populations.