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New Insights into the Transatlantic Slave Trade Through Strontium Research

A fascinating intersection of chemistry and history is emerging as researchers utilize strontium to trace the origins of individuals ensnared in the transatlantic slave trade. This unusual approach involves mapping strontium, a naturally occurring element, throughout sub-Saharan Africa. By comparing findings with strontium levels found in human remains, researchers aim to better determine the geographic origins of enslaved individuals, as detailed in a study published on December 30 in Nature Communications.

The transatlantic slave trade, spanning from the 15th to the 19th centuries, forcibly displaced over 12 million Africans, many of whom departed from major port cities like Lagos in Nigeria and Luanda in Angola. While genetic evidence can trace ancestry, it often fails to pinpoint an individual’s specific upbringing or locality. This limitation has obscured the true origins of many people sold into slavery.

Strontium’s role in this research is critical due to its unique geological properties; the isotope ratios of strontium vary depending on the local geology. Researchers can analyze these variations (known as strontium isotopes) within plant and animal remains, offering insights into the environmental conditions where an organism developed. “It’s in everything and everyone,” states Vicky Oelze, a biological anthropologist at the University of California, Santa Cruz.

The endeavor, led by Oelze alongside fellow researchers, required extensive sampling and analysis over more than a decade, resulting in nearly 900 environmental samples from 24 countries across Africa. Xueye Wang, an archaeologist from Sichuan University in China, highlighted that this significant effort involved over 100 collaborators from various disciplines, including ecology and archaeology.

The project zeroed in on sub-Saharan Africa, a region pivotal not only to archaeological studies but also to conservation efforts, with the added aim of illuminating aspects of the historical slave trade. By applying their comprehensive strontium map, the researchers sought to uncover new information about the origins of those enslaved.

To validate their map’s effectiveness, they analyzed strontium isotope ratios from the dental remains of ten enslaved people interred in Charleston, South Carolina, and Rio de Janeiro. This comparison revealed particulars about individuals previously known only through genetic data. For example, two adult men, Daba and Ganda, who were believed to have West African ancestry, were traced back to more specific regions—southwestern Ivory Coast, southern Ghana, or eastern Guinea—through strontium analysis.

Identifying a person’s geographic roots plays a crucial role in reconstructing their identity and understanding their cultural affiliations. Toubga notes that such determinations facilitate an understanding of the broader cultural and political groups to which these individuals belonged.

While the current study marks a significant achievement, Murilo Bastos, a bioarchaeologist from Brazil’s National Museum, emphasizes that expanding the number of environmental samples could further enhance the map’s spatial resolution. Nevertheless, he recognizes the impressive nature of this research, underscoring its contribution to the field.

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