The AncestryDNA science team presented the results of their latest research today at the Smithsonian Institute’s symposium on The African Diaspora in Washington D.C. Using unique proprietary DNA samples and a variety of statistical approaches, our science team has been able to separate West Africa into six separate population groups based on genetic data. This advancement will provide a finer-resolution genetic ethnicity estimate for individuals with West African ancestry.
AncestryDNA’s six new ethnicity regions of West Africa include Senegal, Mali, Ivory Coast/Ghana, Benin/Togo, Nigeria, and Cameroon/Congo, each of which has a distinct set of tribal affiliations. The division of West Africa into these groups marks the first time that West African genetic ethnicity estimates can achieve this level of detail, bringing AncestryDNA’s total number of reported genetic ethnicity regions in Africa to ten.
The announcement of the new genetic ethnicity regions were presented at The African Diaspora event earlier today by Dr. Jake Byrnes, population genomics senior analyst on the AncestryDNA science team. Although these new ethnicity updates will not be made available to all AncestryDNA users for a few more months, we wanted to give the inside scoop on Jake’s Smithsonian presentation detailing the West African ethnicity update as well as additional research findings on the genetics of African Americans.
It can be extremely difficult to research one’s African ancestry using historical records alone, as most African American individuals in the U.S. are unable to find detailed records of their ancestors before the 1870s. Our AncestryDNA test can help family historians use genetics to pick up where the paper trail ends.
AncestryDNA leverages a unique proprietary collection of DNA samples from individuals with well-documented family trees to conduct innovative research in population genetics, human evolution, and migration. The science behind AncestryDNA is continually evolving and improving. During this ongoing process, the science team demonstrated that genetic data reliably shows population structure in Western Africa. What this means is that the DNA of individuals from Western Africa clusters into a number of distinct groups. As a result, AncestryDNA can now more finely define genetic ethnicity regions in Western Africa. (See the visual representations below.)
Caption: The graph on the left depicts the distinct genetic clusters of individuals from West Africa. Each point is an individual with deep ancestry in West Africa from our proprietary sample database. The color of each point corresponds to the country (shown in the map on the right) where a majority of that individual’s ancestors lived. The x and y axes indicate two primary axes of genetic differentiation (called principal components, or PCs) as inferred from sample DNA. Points closer together on the plot are more similar genetically. Comparison of the graph on the left and the map on the right reveals the similarity of the genetic and geographic structure.
Population structure such as this is not new, and even exists in the U.S today. Here’s an example from the 2010 census data. Each point is an individual, colored by their self-reported ethnicity.
You’ll notice that people of similar backgrounds tend to stay and live in the same general geographic areas. Imagine now if we could roll this map back in time to see where an individual’s ancestors immigrated to the U.S.!
The AncestryDNA science team is looking toward a future where we could reveal, in the absence of a family tree, the most probable locations where one’s ancestors lived – both in the U.S. and abroad. To do this, the science team hopes to harness the power of collectively analyzing family trees of individuals with similar genetic profiles.
Though this project is still in its infancy, the science team has made some progress. First, we looked at the birth locations of individuals in the trees of all African Americans. Then, we looked for locations where, relative to all African Americans, there appeared to be an over-representation of birth locations in trees of individuals with a particular West African ancestry. For individuals with Senegalese genetic ethnicity, we found what seems to be an over-representation of birth locations in South Carolina and Georgia in the 1700’s and 1800’s.
This might be an example where the genetics matches up with history. In the 18th century, plantation owners in South Carolina and Georgia knew little about rice cultivation and preferred to import slaves from Sierra Leone, Gambia, and Senegal (the Windward Coast), where rice is a commonly grown crop. It is thought by some scholars that the Gullah people, who today live in coastal Georgia and South Carolina, descend from slaves imported from the Windward Coast to work specifically on rice plantations.
Providing more detailed ethnicity estimates for West African populations is crucial for American family historians. Approximately 85-90% of today’s African Americans are descendants of enslaved Africans brought to America between 150 and 450 years ago – leaving many African Americans without a known family history prior to this time. AncestryDNA’s new West African ethnicity update will help to link African American individuals to specific locations in West Africa. In the future, more detailed analyses of genetic data and family trees have the potential to reveal important historical stories.
Thanks to the science team’s findings of genetic structure in West Africa, the new African ethnicity regions will be a breakthrough for many African Americans and may even reunite the origins of disrupted families. But more is to come, as we are only scratching the surface of what is possible.
