What is Back?
The Negrito are several ethnic groups who inhabit isolated parts of Southeast Asia. Their current populations include Andamanese peoples of the Andaman Islands, Semang peoples of Malaysia, the Mani of Thailand, and the Aeta, Agta, Ati, and 30 other groups of the Philippines.
The Negrito peoples show strong physical similarities with some African populations, but are genetically closer to south-east Asian populations. They may be descended from ancient Australoid-Melanesian settlers of Southeast Asia, or represent an early split from the southern coast migrants from Africa.
The appropriateness of using the label ‘Negrito’ to bundle together peoples of different ethnicity based on similarities in stature and complexion has been challenged.
Some studies have suggested that each group should be considered separately, as the genetic evidence refutes the notion of a specific shared ancestry between the “Negrito” groups of the Andaman Islands, the Malay Peninsula, and the Philippines
We have, however, recently investigated the position in the global mtDNA phylogeny of complete genome sequences of eight haplogroups found primarily in the Malay Peninsula, showing that most of them branch directly from the Eurasian mtDNA ancestor lineages ~60,000 years ago and are indigenous and unique to the Peninsula (Macaulay et al. 2005)
Current genetic evidence is beginning to highlight more recent relationships between negrito populations and other, non-negrito populations in the same region, while maintaining some evidence for deeper genetic roots of these populations (Barik et al. 2008; Chaubey and Endicott this issue). These deep lineages may not reflect a common ancestry concurrent with the dispersal out of Africa, as predicted by the negrito hypothesis, but a degree of long-term genetic isolation from neighboring populations. The first study to integrate genotype and phenotype data of a negrito population (Migliano et al. this issue) suggests that, based on genetic variation, the Aeta, Batak, and Agta cluster with other South Asian populations and that their small body size evolved independently of other pygmy populations in Africa or Papua New Guinea.
Four Y chromosome haplogroups C, D, O and N, accounted for more than 90% of the East Asian Y chromosomes, are suggested to have Southeast Asian origins, carried by three waves of migrations