Using Genetic Testing to Better Understand the Trans-Atlantic Slave Trade

Generic image
YouTube screenshot
Generic image
YouTube screenshot

The recent opening of the Smithsonian’s National Museum of African American History and Culture is part of a long and slow national reckoning on race, but some chapters on race are still missing from our nation’s history.

Documenting that history may be aided by a project recently launched by the direct-to-consumer genetics-testing company 23andMe. Our team of scientists at 23andMe will use genetic data of Africans living in the United States to better understand the personal, historical and cultural impact of the trans-Atlantic slave trade, one of the largest forced migrations in human history.

Many details of the history of the slave trade have been painstakingly gleaned from shipping records and myriad other written documents. David Eltis, David Richardson and many others teamed up to create both the Atlas of the Trans-Atlantic Slave Trade and the web-based Trans-Atlantic Slave Trade Database, which summarize numerous documents and paint a vivid picture of the forced movements of African peoples across the Atlantic to various points in the Americas.


And yet the written documents cannot answer all the questions about the slave trade and its impact on the populations in the Americas. For instance:

  • Do all African Americans living in the United States today descend similarly from peoples of all the major source regions in Africa, or are there differences among African Americans in terms of from where in Africa their ancestors came?
  • Although most of the slaves brought from ports in Angola disembarked in Brazil, did descendants of those Angolans end up elsewhere in the Americas?

"Information on the sources of African captives entering the Atlantic slave trade is limited,” said Eltis, an emeritus professor of history at Emory University.

 DNA has the potential to fill in some of that missing information and address many of the questions historians have. Geneticists have begun to investigate some of those questions.


The 23andMe Research Team is home to several geneticists, including myself, Kasia Bryc and Adam Auton. Together the team has decades of experience investigating the genetics of Africans and African Americans. Along with many 23andMe customers looking for their own roots in Africa, we are interested in finding answers to many of these questions. Using data from our customers, combined with publicly available and 23andMe genetic data from African populations, this research could help fill in gaps in our knowledge regarding the forced migrations from Africa.

To move this work along, on Oct. 12, we launched the 23andMe African Genetics Project. The project aims to recruit hundreds of people from several sub-Saharan African regions known to have been involved in the trans-Atlantic slave trade. In addition, the project will recruit people from African countries from which many individuals have emigrated in very recent generations—such as Ethiopia, Somalia and Sudan. Through such recruitment, 23andMe will add to its reference database, thereby enabling our researchers to address questions such as those above.


"Genotyping people of recent African descent is one of the most exciting challenges facing the contemporary science of genetics," commented Henry Louis Gates Jr., Alphonse Fletcher University Professor and founding director of the Hutchins Center for African and African American Research at Harvard University. He is also chairman of The Root.

Of course it’s hard to say what the data will reveal, but by using this new set of genetic data and comparing it to 23andMe’s massive set of data from people across the Americas, researchers may be able to see genetic signals of population movements. In other words, 23andMe researchers hope to identify direct connections between locations in Africa and the Americas. This could allow 23andMe researchers to make those connections on a much larger scale than has been possible previously, one that looks not only across Africa but also across the Americas, possibly adding important details to the historical record.


The project will not only support research into the history of the trans-Atlantic slave trade but also enhance what 23andMe can report to customers about their roots in Africa. That could be powerful information for many people searching for their connections to Africa.

At 23andMe we have seen how valuable DNA, in combination with written records, can be in shedding light on both human history and personal stories. The 23andMe African Genetics Project will look beyond the written record to find genetic links between ethnic groups from specific regions in Africa and peoples living in the Americas. If we find any patterns or signals in the data, those signals may help us better understand history at both the personal and population levels.


The Root aims to foster and advance conversations about issues relevant to the black Diaspora by presenting a variety of opinions from all perspectives, whether or not those opinions are shared by our editorial staff.

Joanna Mountain, Ph.D., senior director of research at 23andMe, oversees research projects, ensures the protection of research participants and works with the team that develops ancestry product offerings at the company. Prior to joining 23andMe, Mountain served on the faculties of the anthropological-sciences and genetics departments at Stanford University. She has been awarded multiple grants from the National Science Foundation and the National Institutes of Health and has co-authored over 50 papers in the field of human genetics. Mountain spent two years in Kenya as a Peace Corps volunteer and continues to be particularly interested in the genetic diversity of Africans and African Americans.

Share This Story

Get our newsletter