Genetic Chaos

Friday, February 25, 2005

MtDNA from extinct Tainos and the peopling of the Caribbean

Tainos and Caribs were the inhabitants of the Caribbean when Columbus reached the Americas; both human groups became extinct soon after contact, decimated by the Spaniards and the diseases they brought. Samples belonging to pre-Columbian Taino Indians from the La Caleta site (Dominican Republic) have been analyzed, in order to ascertain the genetic affinities of these groups in relation to present-day Amerinds, and to reconstruct the genetic and demographic events that took place during the peopling of the Caribbean.

Twenty-seven bone samples were extracted and analyzed for mtDNA variation. The four major Amerindian mtDNA lineages were screened through amplification of the specific marker regions and restriction enzymatic digestion, when needed. The HVRI of the control region was amplified with four sets of overlapping primers and sequenced in 19 of the samples. Both restriction enzyme and sequencing results suggest that only two (C and D) of the major mtDNA lineages were present in the sample: 18 individuals (75%) belonged to the C haplogroup, and 6 (25%) to the D haplogroup. Sequences display specific substitutions that are known to correlate with each haplogroup, a fact that helped to reject the possibility of European DNA contamination. A low rate of Taq misincorporations due to template damage was estimated from the cloning and sequencing of different PCR products of one of the samples. High frequencies of C and D haplogroups are more common in South American populations, a fact that points to that sub-continent as the homeland of the Taino ancestors, as previously suggested by linguistic and archaeological evidence. Sequence and haplogroup data show that the Tainos had a substantially reduced mtDNA diversity, which is indicative of an important founder effect during the colonization of the Caribbean Islands, assumed to have been a linear migratory movement from mainland South America following the chain configuration of the Antilles.

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