Historical records are often used to learn about ancestry but a new approach, using genetics, is currently being applied. In a recent study, published in PLOS Genetics, scientists from the Stanford University School of Medicine and the University of Miami Miller School of Medicine compared patterns of genetic variation found in populations in and around the Caribbean. They were able to discern an influx of European genes into the native population that occurred within a generation of Columbus' arrival, as well as two geographically distinct pulses of African immigration that correspond to the beginning and height of the trans-Atlantic slave trade.
The results demonstrate how deciphering genetic echoes from the distant past can illuminate human history. They also emphasize why some populations, such as Latinos, who may be presumed to share largely common ancestry by medical researchers, can display marked differences among populations in susceptibility to diseases or responses to therapeutic drugs.
The group led by Carlos Bustamante and Eden Martin documented genetic variants found among 251 people of Caribbean descent living in South Florida and 79 native Venezuelans representing three native South American tribes. They then compared them with genetic variants 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. This approach allowed them 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 the sub-continental level (think not 'Africa', but 'coastal West Africa', for example).
Co-author Andres Moreno-Estrada comments "All this affects what we call a genetic-mapping strategy to identify disease variants specific to population subgroups, for example; those individuals with more European influence may be at increased risk for certain diseases because that genetic contribution was made by only a few individuals. Or, perhaps Caribbeans with more African ancestry may share an increased risk of diseases with others from West Africa. We're not yet at the point where we are able to say which populations are most likely to have specific diseases, but now we can begin to figure out the important components." 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.