Assertion (A): The mtDNA haplogroups M31 and M32 observed in the Onge and Great Andamanese populations represent ancient maternal lineages that have undergone in situ evolution on the Andaman Islands, isolated since the initial Out-of-Africa coastal migration about 50,000–70,000 years ago.
Reason (R): Complete mtDNA sequencing revealed that the coding-region mutations defining M31 and M32 do not overlap with those of known Indian, East Asian or Oceanian haplogroups M, N or R, and surveys of over 6,500 mainland Indian mtDNA sequences confirmed the absence of these specific mutations, indicating phylogenetic independence driven by genetic drift in small, isolated populations.
- A(A) is false, but (R) is true
- BBoth (A) and (R) are true, but (R) is not the correct explanation of (A)
- CBoth (A) and (R) are true, and (R) is the correct explanation of (A)
- D(A) is true, but (R) is false
Show answer and explanation
Correct answer: (c) Both (A) and (R) are true, and (R) is the correct explanation of (A)
Explanation
Both statements are true, and (R) explains (A).
The Onge and Great Andamanese people of the Andaman Islands carry the mitochondrial DNA (mtDNA) lineages M31 and M32. Complete mtDNA sequencing (Thangaraj and colleagues, 2005) found that the mutations defining these lineages are not shared with Indian, East Asian or Oceanian groups and are absent from thousands of mainland Indian samples.
This shows that the lineages have evolved in isolation on the islands since the early coastal migration of modern humans out of Africa, about 50,000–70,000 years ago, with genetic drift acting in small, isolated populations. mtDNA passes only from mother to child, so it traces the maternal line.