Response to Comment on "Reconstructing the Origin of Andaman Islanders"

doi:10.1126/science.1120670

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Response to Comment on "Reconstructing the Origin of Andaman Islanders"

Kumarasamy Thangaraj,¹^* Gyaneshwer Chaubey,¹^,2 Toomas Kivisild,² Alla G. Reddy,¹ Vijay Kumar Singh,¹ Avinash A. Rasalkar,¹ Lalji Singh¹^*

The mitochondrial DNA coding region substitutions shared bythe Andamanese and two Rajbanshi individuals suggests the earlysplit of M31 from some continental Indian mitochondrial DNAlineages at the time depth 11/14 of the age of haplogroup M.This is still consistent with the ancient isolation of thesegene pools, albeit not as early as the initial phase of humanmigration out of Africa.

¹ Centre for Cellular and Molecular Biology, Hyderabad-500 007, India.
² Estonian Biocenter, Riia 23, Tartu-51010, Estonia.

^* To whom correspondence should be addressed. E-mail: thangs{at}ccmb.res.in (K.T.); lalji{at}ccmb.res.in (L.S.)

Our recent study on Andaman and Nicobar islanders identifiedtwo more mitochondrial DNA (mtDNA) lineage groups, M31 and M32,present in Andaman islanders and absent in 6500 samples fromthe Indian subcontinent (1). The Andamanese sequences of thesetwo haplogroups shared their most recent common ancestor (MRCA)within these haplogroups at time depths 3000 years [confidenceinterval (CI) 2] and 12,000 years (CI 4), respectively, whilesharing the MRCA with continental Indian mtDNA lineages nestedwithin haplogroup M at a time depth of 65,000 years (CI 7).Given these data, the settlement of the Andaman islanders bya population carrying M31 and M32 founders could have happenedany time after the out-of-Africa migration of modern humans.The lack of related lineages in the Indian subcontinent, aswell as elsewhere in the world, led us to suggest that the initialsettlement of the Andaman islanders could have taken place atthe time of coastal migration.

Further screening of Indian populations by Palanichamy et al.(2) has revealed two individuals of the Rajbanshi populationfrom West Bengal sharing 3 out of 14 mtDNA coding region substitutionsspecific for the Andamanese haplogroup M31 (Fig. 1). With verybroad error limits, this finding suggests that the AndamaneseM31 lineages share a common ancestor with some continental IndianmtDNA lineages at the time depth 11/14 of the age of haplogroupM (approximately 50,000 years, assuming 65,000 years for theage of M), which is still consistent with an ancient isolationof these gene pools but not as early as the initial phase ofthe out-of-Africa migration.

Fig. 1. Maximum parsimonious tree of Great Andamanese, Onge, and Rajbanshi reconstructed on the basis of complete mtDNA sequences from the M31 lineage. The Rajbanshi sequence was taken from Palanichamy et al. (2). [View Larger Version of this Image (30K GIF file)]

Taken together, the finding of M31-related lineages in continentalIndia (2) clearly demonstrates that the absence of evidencefor a clade is not the evidence of absence of that clade, evenwhen the sample size exceeds 6000 for a population with thegenetic structure of India. We note as well that our sampleof 107 Rajbanshi (3) did not include any M31-related samples.

References and Notes

1. K. Thangaraj et al., Science 308, 996 (2005).[Abstract/Free Full Text]
2. M. G. Palanichamy et al., Science 311, 470 (2005); www.sciencemag.org/cgi/content/full/311/5760/470a.
3. K. Thangaraj et al., unpublished data.

Received for publication 20 October 2005. Accepted for publication 28 December 2005.

The editors suggest the following Related Resources on Science sites:

In Science Magazine

BREVIA Reconstructing the Origin of Andaman Islanders: Kumarasamy Thangaraj, Gyaneshwer Chaubey, Toomas Kivisild, Alla G. Reddy, Vijay Kumar Singh, Avinash A. Rasalkar, and Lalji Singh (13 May 2005)
Science 308 (5724), 996. [DOI: 10.1126/science.1109987]
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