Massive trove of shipwrecked ivory offers clues to elusive elephants' history

December 16, 2020
Raw elephant tusks from the 16th century Bom Jesus shipwreck. (National Museum of Namibia)

Raw elephant tusks from the 16th century Bom Jesus shipwreck. (National Museum of Namibia)

Researchers learned important new information about the historical behavior of African forest elephants in a first-of-its-kind study of a trove of ivory discovered in a 16th-century Portuguese shipwreck, expanding data available about the species in ways that could aid conservation efforts.

In a study published online Thursday and appearing in the Feb. 8, 2021, issue of Current Biology, an international team of interdisciplinary researchers used DNA analysis and other techniques to trace the origins of 44 tusks found on the ship, which contained the largest archaeological cargo of African ivory ever found.

Contemporary African forest elephants are known to sometimes utilize habitats outside the deep forests where they’re typically found. That was thought to be a more recent development due to the large-scale decimation of the animals, which are classified as vulnerable by the International Union for the Conservation of Nature, in the 19th century. 

“What we’re actually showing is this is not a new thing at all,” said Alida de Flamingh, a postdoctoral research associate at the University of Illinois at Urbana-Champaign and first author of the study. “We used DNA and isotopes to determine where the elephants from which these tusks were harvested lived before they were killed.”

The isotope data, which vary based on what plants the elephants ate and the amount of rainfall in their environments, revealed how forest elephant populations were living in mixed-vegetation habitats around the time of the shipwreck. Those areas are characterized by the presence of both forest-like trees and savanna-like grass. The finding squared with the fact that Portuguese trading ports along the West African coast were surrounded by this type of vegetation.

Just four of the 17 elephant lineages tied to tusks analyzed in the study, all of which were determined to come from West Africa, are still known to exist on the continent. More than 95% of West African elephants have disappeared since the wreck because of hunting and habitat destruction.

“One of the main things we found is that it seems like the populations that lived in West Africa in the 1530s, they had a much higher genetic diversity,” de Flamingh said. “It’s concerning … It just recapitulates that conservation efforts definitely need to focus on preserving the remaining genetic diversity that we have in West African elephants.”

In these animals’ unique, matriarchal social structure, offspring live with their mothers within herds, staying in the same geographic area for a very long time. By extracting a genetic marker in the form of mitochondrial DNA from the tusks, which an animal can only get from its mother, and comparing it to a dataset spanning the continent, the researchers were able to trace the tusks to West Africa.

Now, the team is adding the DNA sequences to the Loxodonta Localizer, an open-access tool that was developed at the university with help from de Flamingh and her colleagues and uses the same principle to let any researcher search for the closest matches across Africa.

In this way, officials examining vast shipments of illegal ivory can also zero in on where it came from to inform anti-poaching efforts.

The wreck of the Bom Jesus was discovered in 2008 when a company mining the west coast of Africa along Angola, Namibia and into South Africa reported spotting the rich collection of artifacts, which also included rosaries, gold and metal coins and even a hippopotamus tooth, among other things. The ship is officially recorded as having sunk in 1533, based on its contents.

Having a team of archaeologists and isotope, ancient DNA and elephant genetic experts from Namibia, South Africa, the U.K. and U.S. made it possible to answer questions that they otherwise wouldn’t have been able to address, much less answer, de Flamingh said.

“It’s quite a rare thing to have such complementary skill sets in researchers,” she added. “I think what makes it unique, this study, is that the interdisciplinary fields really complement each other. They answer questions that the other fields pose.”

The study “Sourcing Elephant Ivory from a Sixteenth-Century Portuguese Shipwreck,” published online Dec. 17 and in the Feb. 8, 2021, issue of Current Biology, was authored by Alida de Flamingh, University of Illinois at Urbana-Champaign; Ashley Coutu, University of Cape Town, University of Oxford and University of York; Judith Sealy, University of Cape Town; Shadreck Chirikure, University of Cape Town and University of Oxford; Armanda D.S. Bastos, University of Pretoria; Nzila M. Libanda-Mubusisi; Ripan S. Malhi, University of Illinois at Urbana-Champaign; and Alfred L. Roca, University of Illinois at Urbana-Champaign.

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