Reference Stanford researchers finding caribbean roots using genetics

Discussion in 'Genetics' started by parvathy, Nov 15, 2013.

  1. parvathy

    parvathy Member

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    Those of us who want to learn about our ancestors - who they were, where they came from and how they mingled (or didn't) with others around them - often turn to historical records or elderly family members for answers. But a new study by researchers at the Stanford University School of Medicine and the University of Miami Miller School of Medicine indicates that the answers can also be found within our own genes.

    The researchers compared patterns of genetic variation found in populations in and around the Caribbean, which has had a particularly tumultuous past since Christopher Columbus stumbled into the Bahamas in 1492. Not only did they identify an influx of European genes into the native population that occurred within a generation of Columbus' arrival, but they also discovered two geographically distinct pulses of African immigration that correspond to the beginning and height of the transatlantic slave trade.

    The study demonstrates how deciphering genetic echoes from the distant past can illuminate human history. But it also helps explain why some populations, like Latinos, who may be classified by medical researchers as a single group, display marked differences among populations in susceptibility to diseases or responses to therapeutic drugs.

    Moreno-Estrada is the lead author of the study, published Nov. 14 in PLOS Genetics. Carlos Bustamante, PhD, professor of genetics at Stanford, shares senior authorship with Eden Martin, PhD, of the University of Miami.

    The group, led by Bustamante and Martin, documented genetic variants found in 251 people of Caribbean descent - representing Cuba, Puerto Rico, Haiti, the Dominican Republic, Honduras and Colombia - living in South Florida, and 79 Venezuelans representing three native South American tribes. They then compared the genetic variants with those found in more than 3,000 Native Americans, Europeans and Africans.

    To conduct the research, the team devised a new way of analyzing DNA to infer genetic ancestry at a fine geographic scale. Using this approach, they were able to estimate not just what proportion of each individual's genome was derived from each continent, but also to determine the closest ancestral group at a more-regional level.

    The approach allowed the researchers to categorize regions of DNA as not just European, for example, but Iberian. Or not just African, but West African. They could also estimate when each mixing event occurred by assuming longer segments had been incorporated more recently than shorter segments. That's because, over time, our chromosomes randomly swap regions during cell division, breaking apart and mixing up formerly long, contiguous stretches of DNA. The more time that passes, the greater the likelihood that any one piece will be disrupted by this recombination process.

    The research confirmed much of what is known about the history of the Caribbean islands. But it also answered some long-standing questions about the ancestry of native Caribbean people, the impact of European colonization, and the timing and geographic origins of forced African immigration.

    The researchers found, for example, that the Caribbean was first populated by people from inland South America about 2,500 years ago. Their DNA mirrors that of Amazonian tribes in the interior of the continent, and this flow of genes matches what is known about how language spread across the region during that time.

    The European component, which was introduced 16 to 17 generations ago (or about 500 years ago - roughly when Columbus reached the islands) matches, but does not exactly mirror, the range of genetic diversity in modern-day Iberia. This finding most likely indicates that a small number of Europeans settled in the Caribbean and contributed their DNA to future islanders. It also confirms that, after the initial colonization of the Caribbean islands, future waves of immigration from Europe primarily came to the mainland.

    Finally, African genetic diversity was first introduced to the Caribbean population about 15 generations ago (about 1550), when the first enslaved Africans were brought to the islands. The second pulse occurred five to seven generations ago, during the late 18th century, at the height of the transatlantic slave trade. The origin of the first pulse arose from the north coast of West Africa, whereas the second originated from central coast of West Africa.

    As exciting as it is to use genetics to answer age-old historical mysteries, it's the potential contribution of this knowledge to medicine that has captured the researchers' interest.

    Other Stanford co-authors include former postdoctoral scholar Simon Gravel, PhD; former graduate student Fouad Zakharia, PhD; postdoctoral scholars Jake Byrnes, PhD, and Karla Sandoval, PhD; graduate student Patricia Ortiz-Tello; senior research scientist Paul Norman, PhD; and Peter Parham, PhD, professor of structural biology and of microbiology and immunology.

    Reference : Reconstructing the Population Genetic History of the Caribbean DOI: 10.1371/journal.pgen.1003925
    Arul Prakash likes this.
  2. Arul Prakash

    Arul Prakash Sharing Knowledge Staff Member Full Member

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    I know National Geographic did similar research. Finding roots does have its scientific value as much as it's being overshadowed by the emotional side.

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