Andamanese represent world's most ancient isolated human population after Khoisan. Negritos diverged early post-Toba eruption 73,000 years ago. Haplogroup M dominates Andamanese, absent or rare outside southern Asia. M2 coalesces at 63,000 years ago, M4 at 32,000 years ago. Andaman M2 variants unique, absent in modern Indians, indicating in situ evolution. Phenotypic resemblance to African pygmies convergent, not genetic. Genetic data refutes independent convergence of Negrito traits across Asia. Negritos form ancient pan-Asian layer pushed to margins by later migrants. Closest relatives: Aeta, Semang, Vedda, Shompen via shared haplogroups and metrics. Genetic distances rank Aeta closest to Andamanese Negritos. High blood group A in Andamanese Onge links to Melanesians and ancient SE Asian elements. Short stature standardized from long isolation: Andamanese males average 148cm. mtDNA supports two founding events or extreme substructure in Andamans. Negritos possibly first sapiens to encounter Homo erectus in Asia. Haplogroup M cline in India traces early southern route matching Negrito distribution. Andamanese isolation preserved basal M lineages lost on mainland.