African origins and the genetic legacies of the Caribbean Taino, an “extinct population” ??

The Caribbean was one of the last parts of the Americas to be settled by humans, but how and when the islands were first occupied remains a matter of debate. Authors (see 2o17 article attached) comprehensively compared the mitochondrial DNA (mtDNA) compositions of inhabitants of present-day Cuba, Dominican Republic, Haiti, Jamaica and Puerto Rico. Such mtDNA-typing is often by forensics scientists to match DNA from an unknown sample to that collected at a crime scene; mtDNA-typing is also ideal when the DNA is degraded, or the sample does not contain enough genomic nuclear DNA (gDNA) for analysis. Also, mtDNA is single-stranded. Because mtDNA is maternally inherited, the DNA from siblings and all maternal relatives should be identical (in the absence of spontaneous mutations). In addition, generally there is a lack of recombination, an event that occurs frequently during gDNA cell division, in which the two stands of DNA cross over and exchange information, thereby creating greater sequence diversity. Hence, even matriarchal relatives separated by several generations can serve as reference samples.

The TAINO maternal DNA was found to be prominent in the ex-Spanish colonies (22-61%), whereas it is basically non-existent in the ex-French and ex-English colonies of Haiti (0.0%) and Jamaica (0.5%). The most abundant Native-American mtDNA haplogroups (segments of contiguous DNA showing a single line of descent, usually dating back thousands of years, most commonly studied in Y-chromosome (Y-DNA) haplogroups and in mtDNA) are almost fixed in Haiti and Jamaica, while the frequencies of specific African haplogroups varied considerably among the five island nations. The strong persistence of Taino mtDNA in the ex-Spanish colonies, and its absence in the French and English ex-colonies, is likely the result of different social norms regarding mixed marriages with Taino women during the early years after the first contact with Europeans.

Authors (see 2o18 article attached) report the genome sequence of a 1,000-year-old Lucayan Taino woman recovered from a site in the Bahamas. They sequenced her genome and found that she is genetically most closely related to present-day Arawakan speakers from northern South America –– suggesting that ancestors of the Lucayans originated there. Furthermore, authors found (in this ancient genome) no evidence for recent inbreeding or isolation, suggesting that the Lucayans had a relatively large effective population-size. Lastly, authors show that the Native-American components in some present-day Caribbean genomes are closely related to the ancient Taino, demonstrating an element of continuity between pre-contact populations and present-day Latino populations in the Caribbean.

Gene Dec 2o17; 637: 33–40 & Proc Natl Acad Sci USA 6 Mar 2018; 115: 2341–2346

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