Summary of the Ancient DNA Research on the Anson Street Ancestors
Over the past five years, anthropological geneticists Drs. Raquel Fleskes and Theodore Schurr have been working to analyze the DNA extracted from the Anson Street Ancestors. We are very happy to report that the second phase of the research is now complete and has been summarized in an article now appearing in the Proceedings of the National Academy of the Sciences entitled, “Community Engaged Ancient DNA Project Reveals Diverse Origins of 18th Century African descendants in Charleston, South Carolina.”
If you click on the accompanying link, you will be able to access and read the article.
On behalf of the Anson Street African Burial Ground Research Team, we want to sincerely thank everyone who participated in this project and supported the work at Anson Street. This was a community effort and we are pleased to contribute new knowledge about persons buried at this burial site. We hope that the PNAS study helps to inform the important history and legacy of African descended persons in Charleston and the United States more broadly.
What did we know before?
The Anson Street African Burial Ground was accidently uncovered during construction of the Gaillard Auditorium in downtown Charleston. A total of 37 burials were identified, with 36 containing the remains of once living humans. The burials were spaced into roughly four rows, and each contained a burial of one individual. Archaeological evidence of coffin nails, burial shrouds, and jewelry all suggest that they were buried with care.
These burials were approximately dated to between 1760 and 1790 CE based on burial artifacts and archival records. We know that the land on which the burial ground was discovered was historically the property of a white landowning individual in the northern-most boundary of Charleston. All burial grounds for Free People of Color during this period were located in a different area of the city, suggesting that these individuals were likely enslaved.
Analysis of their bones (osteology) showed that men, women, and children were buried at the site. These bones also indicated that the individuals were likely of African descent. There is no evidence in the bones that reveals how they might have died. The analysis of the teeth of the Ancestors showed that they did not have the best dental health since many of them had cavities and tooth loss, most likely due to poor dental care. Some of the individuals had tooth modifications for ritual purpose (tooth filing for Ganda) or due to wear.
We were also able to determine if the Ancestors were born in Africa or instead outside of Africa based on the strontium isotopes signature in their bones and teeth. Strontium isotopes reflect a unique geographic signature based on the ground water and food that they were eating. The isotope data showed that six Ancestors were born in Africa, while the rest were likely born in Charleston or outside of Africa. Most of the Ancestors lived a majority of their lives outside of Africa, as well (i.e., Charleston). The only individual who likely passed away shortly after arriving in Charleston was Ganda.
Initial DNA analysis of the Ancestors focused on the mitochondrial DNA. The mitochondrial DNA (mtDNA) is a small piece of DNA that is directly passed from mothers to daughters in each generation, thereby allowing us to learn about the maternal history of the person. We found that a majority of the individuals had mtDNAs that are found in contemporary African populations today. However, one individual (Coosaw) contained a mtDNA that commonly appears in Native American populations. This finding suggests that she had Native American maternal ancestry.
In addition, two individuals shared the same mtDNA type. This was an adult female (Isi) and a child (Welela), who were buried right next to each other. This fact may suggest that they shared a mother-child relationship. All of the other individuals had different mtDNAs, suggesting that they were not maternally related.
More information about these findings have been published in the American Journal of Physical (Biological) Anthropology, which can be found here.
What did we do for this study?
For this study, we built upon our previous research on the burial ground and combined it with more detailed genomic analyses of the Ancestors. We were able to obtain whole genomic sequence information for 18 out of the 36 Ancestors. These results allowed us to explore the bi-parental (total) genetic ancestry of and biological relatedness of these 18 Ancestors.
What did we find?
History of Charleston in the Trans-Atlantic Slave Trade
To better understand the origins of African descended people in Charleston who were abducted and brought to Charleston, we analyzed the records in the Slave Voyages Database (https://www.slavevoyages.org/). This publicly available database contains slave ship registers for a majority of voyages coming to North America. Thus, we were able to analyze how many individuals were forcible taken and from what areas of Africa they were taken. We found that people from all over the western coast of Africa were brought into Charleston. A map showing the different places and the numbers of people are shown below.
Diverse African Ancestry of the Anson Street Ancestors
We observed that the Anson Street Ancestors were very diverse and reflected genetic ancestry from all over the western coast of Africa. Some Ancestors were more similar to populations in the Gambia, such as Lisa, and others were more closely related to population in the Upper Gold Coast, such as Daba and Nana. We conducted a principal component analysis, which plots DNA data to determine how similar individuals are to each other. In the graphic below, you can see the black dots representing the Ancestors fall with different colored dots representing different populations in Africa. This finding is important as it indicates that the Anson Street Ancestors came from many places in Africa, and not just one location.
Native American Ancestry in one individual
As noted earlier, we determined that one individual, Coosaw, had Native American ancestry. This finding is congruent with the previous mtDNA evidence, which showed that she had a mtDNA haplogroup (maternal lineage) that appears in Native American populations today. Her genomic information indicated that approximately one third of her ancestry was affiliated with Native American populations, with rest being African in ancestry. All together, these findings mean that a few generations ago one of her maternal grandparents was of Native American descent.
Mostly Men were found at the Anson Street African Burial Ground
Given that genetic males have a Y chromosome, and genetic females do not, we tested for the presence of Y chromosomal DNA in the Anson Street Ancestors to determine what their genetic sex was. We found that 21 of 36 individuals were genetically male.
No evidence of genomic relatedness between the individuals
We did not find any evidence of relatedness between any of the 18 Anson Street Ancestors tested in this analysis. Previously, we inferred that Isi and Welela were likely maternally related given that they shared a mtDNA haplogroup (maternal lineage), Unfortunately, we did not have enough genomic data from Welela to verify this connection. Nevertheless, our results suggest that the Anson Street Ancestors were interred over time and not with genetic kin. However, the DNA findings do not negate other relationships or friendships that they may have had – as we know, the Ancestors were interred with love and care based on burial artifacts.
Why is this study important?
This study is important in that it helps us understand the genetic ancestry and origins of the Anson Street Ancestors, and provides critical insight into the histories of African descended persons in colonial North America.