Intra-African conflicts led to the enslavement of hundreds of thousands of Africans during the 19th century, but questions surrounding where those people originated have remained an unsolved mystery.

Historians have known for decades where the enslaved Africans departed Africa, but due to a very limited amount of documents — most from the perspectives of European slave traders — little is known about where the enslaved came from before boarding slave ships.

Researchers at the University of Colorado Boulder believe they are one step closer to answering this question as a team created an interactive map that estimates where people may have been captured and enslaved.

“Just because you fly out of Denver, doesn’t mean you live in Denver,” said lead author Eric Vance, the director and founder of the university’s Laboratory for Interdisciplinary Statistical Analysis (LISA). “So if an enslaved person boarded a ship in Lagos, Nigeria, it doesn’t mean that they’re necessarily from Lagos.”

The research team was led by Vance and Henry Lovejoy, a history professor at the university who runs the Digital Slavery Research Lab. Their findings were on Thursday by the Royal Statistical Society.

The map is a first-of-its-kind as researchers used a mathematical model that estimated conditional probabilities of African origins during the 19th century transatlantic slave trade, according to the university.

Between 1817 and 1833 conflicts during the collapse of the Kingdom of Oyo — located in present day southwest Nigeria — led to the enslavement of an estimated 121,000 people, according to the research article.

To determine where the enslaved people originated, Lovejoy used several databases to acquire detailed shipping records that revealed when and where people people boarded slave trips along the African coast.

He then utilized primary and secondary sources to determine where conflicts took place and how it affected inland migration.

“We’ve only really been able to know where the slave ships departed, but no one has connected it inland until now,” Lovejoy said.

However, due to the scarcity and validity of the data — which mainly came from the perspective of European slavers — required Lovejoy to make some assumptions regarding the data.

“I can’t emphasize enough the amount of uncertain data I’m using,” he said. “I’m trying to be as honest as possible while developing a solid methodology of data collection,” Lovejoy said.

Lovejoy and his lab recognize the implications of mapping Africa in the past as most historical materials during the precolonial period assigned numbers to enslaved person. Additionally, many of the primary sources available “reflect skewed, racially biased perspectives,” according to the university.

“Maps have the potential to be very authoritative, and that’s not what we’re trying to do here,” Lovejoy said. “We want to regenerate identities in a respectful and ethical framework—to do that, we need African involvement.”

Vance has already helped build 35 new statistical collaboration laboratories in developing countries. 15 of those are in Nigeria where the project study is occurring, according to the university. He will also present the maps’ findings at the LISA 2020 Sustainability Symposium in May in Ghana.

Lovejoy hopes to organize more conferences in Africa and partner with local universities to bring students to CU to improve the map by incorporating oral histories and ethnolinguistic data.

“There’s an inherent difference between a foreigner working on a geography versus someone local — especially in context that’s involving a very terrible history of humanity,” Lovejoy said.