Insights into the Trans-Atlantic Slave Trade

The following post is an interesting study that has recently come to my attention and continues a theme from my last post on the Archaeology of the Irish Diaspora. Increasingly, genetic studies are becoming an important source of potential information about the human past.

As noted in my last post, a diaspora is a specific type of mass relocation of people, defined by Brighton and Orser (2006: 64) as "the forced dispersal or scattering of people from a homeland as the result of famine, war, enslavement, ethnic cleansing, conquest, and political repression." Such movements are permanent and multi-generational.

To give one prominent example, between about 1500 and 1850 AD, more than 12 million enslaved Africans were shipped to the Americas as part of the trans-Atlantic slave trade. Certainly there can be little doubt of the impact that this event has had on modern demographics.

Captives being brought on board a slave ship on the West Coast of Africa (Slave Coast). Wood engraving c. 1880. Image sourced here.

Despite extensive historical knowledge about the African slave trade, details about the ethnic and geographical origins of those forced into slavery remain elusive. Historical records - merchant ledgers, shipping records etc. - tend to refer to coastal shipping points rather than the slaves' actual ethnic or geographic origins.

Attempting to use genetics to try and fill some of these gaps in our knowledge, scientists from the University of Copenhagen and Stanford University School of Medicine successfully extracted DNA from the tooth roots of three enslaved Africans who had been buried on the Caribbean island of Saint Martin over 300 years ago. The remains of these three individuals had been unearthed during a construction project in 2010.

A problem with studying the DNA of human remains from tropical environments is that the hot and humid conditions tend to accelerate the deterioration of the genetic material. Initial DNA sequencing efforts in this study rendered short stretches of highly deteriorated DNA.

To get around this problem, the researchers turned to a technique called Whole-Genome Capture to fish out snippets of intact DNA from the mixture.

As explained in the article on the Stanford School of Medicine website (linked above): "The [Whole-Genome Capture] approach exposes the DNA sample to a genome-wide panel of human-specific RNA molecules to which the degraded DNA in the sample can bind. The effect is somewhat like stirring a pile of iron-rich dirt with a powerful magnet to isolate the metal from the soil, and it allowed the researchers to concentrate the ancient DNA for more efficient sequencing."

They then compared the recovered DNA sequences with a reference panel of 11 West African populations to identify the distinct ethnic groups from which each individual likely originated.

The results of the study revealed that one of the skeletons belonged to a man who had likely belonged to a Bantu-speaking group in northern Cameroon. The samples from the other two individuals shared similarities with non-Bantu-speaking groups in present-day Nigeria and Ghana.

Also from the linked article on the Stanford webpage: "We were able to determine that, despite the fact that the three individuals were found at the same site, and may even have arrived on the same ship, they had genetic affinities to different populations within Africa,” said [Maria] Avila-Arcos [one of the study's lead authors]. “They may have spoken different languages, making communication difficult. This makes us reflect on two things: the dynamics of the trans-Atlantic slave trade within Africa, and how this dramatic, ethnic mingling may have influenced communities and identities in the Americas.”

The study has been published in the Proceedings of the National Academy of Sciences.

Thanks for Reading,

Nick.

Reference

Brighton, S. A., & Orser, Jr, C. E. 2006. “Irish Images on English Goods in the American Market: The Materialization of a Modern Irish Heritage.” In I. Russell (ed.), Images, Representations and Heritage: Moving Beyond Modern Approaches to Archaeology, pp. 61-88. New York: Springer.