Andaman Islanders trace Asian origins. Great Andamanese show substructuring from merged tribes plus admixture with mainland Indians and Nicobarese. Great Andamanese and Nicobarese share distant separation but R22 mitochondrial lineage also found in Shompen and Southeast Asians. Nicobarese carry M74b haplogroup from Southeast and East Asia. Onge and Jarawa cluster closely genetically matching linguistic ties. Jarawa recently diverged from Onge via M31 and M32 mtDNA plus autosomal and Y-chromosome differences. Andaman Islanders endured heavy genetic drift from prolonged isolation and inbreeding. Negrito Great Andamanese admixed substantially with non-Negrito Nicobarese per autosomal and mtDNA data.