Genetics
The strongest clues to their origins are mostly derived from genetic analysis, both of nuclear DNA and mitochondrial DNA.
The analysis of nuclear DNA confirms the uniqueness of the Andamanese people. First, they show a very small genetic variation, which is indicative of populations that have experienced a population bottleneck and then developed in isolation for a long period. Second, an allele has been discovered among the Jarawas which is found nowhere else in the world. Third, they present no specific affinity to any other population in the world. This is in contrast to the neighboring Nicobarese, who are believed to mostly descend from more recent immigrants from mainland Asia.
A 2009 genetic study of Indian populations that traced most South Asian ethnicities to genomic contributions from two original founding populations also found that, of all modern-day Indians, only the Andamanese possess Ancestral South Indian lineage without admixture of any Ancestral North Indian genetic heritage.
Read more about this topic: Andamanese People