Almost 500 years ago, in 1533, a Portuguese trading ship carrying 40 tonnes of gold and silver coins, along with other precious cargo, disappeared on a voyage to India.
Known as the Bom Jesus, the archaeological remains of this ship, including much of its cargo, were rediscovered in 2008 off of the African nation of Namibia, close to its infamous Skeleton Coast.
The Bom Jesus is the oldest known shipwreck in southern Africa, but it is its cargo that has set the world’s scientific community abuzz.
Stashed in the hold of the Bom Jesus were more than 100 elephant tusks, ivory that is now being used to give new insights into the herds of elephants that once roamed the bushlands of West Africa.
In a groundbreaking study published this month in the scientific journal Current Biology, a team of international researchers has used this trove of ivory to conduct the first-ever investigation into the origin, ecology, and genetic significance of shipwrecked ivory.
That’s important because ivory was a central driver of the trans-continental commercial trading system connecting Europe, Africa, and Asia using sea routes.
But even more importantly, the study has significant implications for understanding how the elephant population of West Africa has changed during the past 500 years.
“When the ship sank, the copper and lead ingots [stored above the tusks] kind of pushed the ivory down into the seabed,” protecting the tusks from scattering and erosion. A frigid ocean current also runs through this region of the Atlantic. That really cold current probably helped preserve the DNA that was in the tusks,” says researcher Alida de Flamingh from the University of Illinois in the United States.
“We determined where these tusks came from by examining a DNA marker that is passed only from mother-to-calf and comparing the sequences to those of geographically referenced African elephants. By comparing the shipwreck ivory DNA to DNA from elephants with known origins across Africa, we were able to pinpoint the geographic region and species of elephant with DNA characteristics that matched the shipwreck ivory.”
Alida and her colleagues were able to extract DNA samples from 44 available tusks which showed that the ivory had come from African forest elephants. Their mitochondrial DNA, passed down from mother to calf, traced them to 17 or more herds specifically from West Africa.
“In order to fully explore where these elephant tusks originated, we needed multiple lines of evidence,” says Ashley Coutu, from the University of Oxford. “Thus, we used a combination of methods and expertise to explore the origin of this ivory cargo through genetic and isotopic data gathered from sampling the tusks.”
That the ivory should all come from West African origins is a surprise, the team said, because the Portuguese had established trade with the Kongo Kingdom and communities along the Congo River by the 16th century. Their expectation was that the elephants would be from diverse regions across Western and Central Africa.
That the tusks originated from many different herds within the same region suggests that numerous West Africa communities worked to supply the ivory. Yet it remains unclear as to whether Portuguese traders gathered this diverse ivory from several locally sourced ports along the coast, or from a single port linked to extensive trading networks within the continent.
Alida De Flamingh says the new data can now aid in tracing the source of confiscated illegal ivory. And the new findings are just the tip of the iceberg in terms of what might result from studies of ivory about elephants and the people who hunted them, both in the past and today.
Only continued investigations will help solve that mystery.
Feature image: African forest elephant (Loxodonta cyclotis) via Nicholas Georgiadis