Project collaborators collect samples from termite mounds in Ivory Coast. Strontium ratios are like a unique “geological fingerprint” that is reflected in the environment and organisms of a particular region. This map models these values based on data from 11 predictor variables and over 2,000 samples. Credit: Vicki Else
A team of researchers led by the University of California, Santa Cruz recently published a sophisticated new map that reveals for the first time the unique “geological fingerprint” of much of the African continent.
This map helps archaeologists, conservation scientists, and forensic experts match artifacts and plant, animal, and human remains found in locations around the world to their most likely place of origin within Africa. , provides new insights on a variety of issues from Atlantic history. From the transatlantic slave trade to modern wildlife trafficking and human migration patterns.
A demonstration of the research team's method and some of the map's capabilities has been published in the journal Nature Communications. The map is available to the public through open access. This is the first bioavailable strontium isotope map showing predicted strontium isotope ratios across sub-Saharan Africa.
Strontium is an element found in rock and soil and exists in several different chemical forms called isotopes. The ratio of these isotopes to each other indicates the age and chemical composition of the rock in a particular region of the Earth. Organisms incorporate strontium from the environment into their tissues at rates that reflect the local conditions where they developed. This could be due to researchers performing isotope analysis on samples of unknown origin and using the new isotope map to determine which region of sub-Saharan Africa produced the specific ratios observed in the samples. This means you can see which is the highest.
To develop the map, researchers used computer modeling techniques that incorporated 11 predictor variables and strontium isotope data from more than 2,000 samples collected across the African continent. The project took more than 10 years to complete and required international coordination by more than 100 scientists.
There has been a great need for strontium isotope mapping in sub-Saharan Africa for many years, said Vicki Elze, a professor of anthropology at the University of California, Santa Cruz, who conceived the project and is senior author of the new paper. Isotope analysis can greatly enhance our understanding of global human and wildlife movement. This is particularly important for a region that was a center of human exploitation and trafficking during the Atlantic Slave Trade era and is now home to numerous endangered species and trafficked wildlife.
But Else said the region has long been suffering from a lack of scientific equipment to conduct on-site analyses, as well as a lack of overall samples due to logistical issues and, in some cases, security risks from armed conflict. He said that they were facing “marginalization.”
“When we started this project, there were only two data points in all of West Central Africa, and both were in Nigeria,” she explained. “Essentially, at the time, we were not able to use this type of analysis to investigate the big issues across West and Central Africa because there was no baseline information available. This has long been an inequity. It was also a missed opportunity, because the geology of west-central Africa is very diverse, making it a perfect landscape to use this technique.”
To develop the new map, Else and her team used previously available strontium isotope data for parts of southern and eastern Africa, as well as data from Angola that the core team published in 2023, and data from western and eastern Africa. They combined new data from 778 samples collected in 24 countries in the Midwest. Africa. The team's research provided the first known strontium isotope data for 16 of these countries.
The new samples used in this project include wild plants, soil, bones, teeth, and snail shells, primarily made by postdoctoral researcher Xueye Wang and graduate students in the UC Santa Cruz lab. and processed and analyzed by undergraduate students. Samples were provided through a partnership with the Pan African Program, which was collecting environmental samples for chimpanzee research projects, and through sample recruitment to the Society of Africanist Archaeologists.
The new data now allows the team to build powerful predictive models for the map. To explore its historical applications, researchers collected the remains of first-generation enslaved people buried at the Anson Street African Cemetery in South Carolina and the Pretos Novos Cemetery in Rio de Janeiro, Brazil. The samples were analyzed for strontium isotope ratio. By combining historical, genetic and other lines of evidence with new strontium isotope maps, the researchers were able to predict the likely region of origin for each person with far greater specificity than previously possible. I was able to.
“One of the main questions descendants of enslaved people still have today is wanting to know more about where their ancestors came from, and our research provides some of those answers. “It helps provide that,” Else said. “Sub-Saharan Africa is a big place with very diverse cultures, so it's really important to be able to identify, for example, whether someone is probably coming from the Angola plateau or from the southern coast of Ghana. It tells us something about a person's life history that helps us better understand these ancestors and how their legacy contributes to people living today. ”
Xue Wang, a postdoctoral researcher at the University of California, Santa Cruz, who previously studied with Else and is the lead author of the current paper, said the team's efforts helped victims of human trafficking who were systematically dehumanized by the transatlantic slave trade. He said he hopes it will help restore his identity.
“Through this research, we aimed to go beyond academic research to reclaim the voices of those silenced by history and give them a rightful sense of belonging,” she said. “These results encourage more researchers to use strontium isotopes and other methodologies to help restore the identities, cultures, and livelihoods of individuals and communities who were deprived of their rights and livelihoods during the colonial era. I look forward to it.”
The map not only sheds new light on history, but also serves important modern-day applications, such as combating wildlife trafficking. Animal parts seized in the illegal wildlife trade can be analyzed for strontium isotope ratios and compared to maps, allowing conservationists and law enforcement to better understand the geographic locations of poaching and smuggling networks they are trying to shut down. It helps identify potential locations.
Researchers also hope the map can be used in forensic analysis of the bodies of the thousands of people who tragically drown in the Mediterranean each year while trying to migrate to Europe. If their origins can be traced, their bodies could be repatriated for a proper burial in their homeland.
Oelze expects the maps to become even more useful over time as more data becomes available for each of these applications.
“We remain very interested in obtaining more samples from the remaining data-poor areas of the African continent, such as the Sahel, Sudan and Mozambique,” she said. “We will continue working closely with local archaeologists to fill data gaps. In the meantime, we hope this project will have a positive impact.”
Reprinted courtesy of the University of California, Santa Cruz.
