A trove of elephant tusks found in the cargo hold of an old Portuguese shipwreck is yielding new insights into the 16th-century ivory trade and lost African elephants.
In 2008, workers with a diamond mining company, while bulldozing a beach in Namibia, accidentally discovered the Bom Jesus, a Portuguese merchant vessel that disappeared in 1533. The ship, filled with gold, silver, tin, ivory, and 44,000 pounds of copper ingots, sank while en route to India.
For centuries, those heavy copper ingots pushed the ship downward and into the soft seafloor, creating ideal conditions for preservation. The cold waters along the coast of southwest Africa did the same. This resulted in the exquisite preservation of over 100 elephant tusks pulled from the ship’s cargo hold, in what is the largest archaeological discovery of African ivory ever found.
New research published today in Current Biology provides a detailed analysis of these tusks, revealing the elephant species and family groups targeted for this ivory, along with the elephants’ geographic location and preferred habitats. A key finding of the new study is that many distinct herds roamed West Africa at the time, the majority of which are now gone. The new paper also adds to our understanding of the early 16th-century transcontinental ivory trade.
This study, co-authored by geneticist Alida de Flamingh from the University of Illinois at Urbana-Champaign, is quite groundbreaking, requiring archaeologists, historians, paleogeneticists, and isotope specialists to make sense of this extraordinary find.
The new study “provides a framework for examining the vast collections of historic and archeological ivories in museums across the world,” de Flamingh explained in an email. As an example, the methods used in the new study can now “be used to investigate ivory cargo reported from the Mediterranean Sea and the Atlantic, Pacific, and Indian Oceans,” she said. What’s more, the historic and archaeological study of ivory “affords a window into human-animal relationships across thousands of years,” and it can reveal the “patterns of interaction and exchange between people who lived oceans apart.”
The team, which included researchers from the University of Oxford and University of Cape Town, managed to conduct a DNA analysis on 44 tusks pulled from the Bom Jesus and an isotopic analysis on 97 tusks. The genetic work (which included a comparative analysis with DNA taken from living elephants) allowed them to identify species and haplogroups (family groups with distinct genetic signatures), while the isotopic work allowed them to pinpoint where these elephants lived in Africa.
Results showed that ivory onboard the Bom Jesus was exclusively sourced from African forest elephants. Mitochondrial DNA (DNA passed down from mother to child), linked the ivory to at least 17 genetically distinct groups living in western Africa, as opposed to central Africa, which makes sense.
“These ancient forest elephants were killed for their ivory in West Africa and not in Central Africa, a finding consistent with the establishment of Portuguese trading centers along the West African coast during this period of history,” said de Flamingh.
Of the 17 mitochondrial haplotypes identified, only four can still be found today in living elephants. The missing lineages are likely the result of excessive hunting and loss of habitat, according to the researchers.
These elephants lived in a mixed forest environment, switching from forested areas to savannas depending on the season or availability of water. This was an unexpected result, as de Flamingh explained.
“Isotope characteristics of the shipwreck ivory produced a surprising result: even though these are African forest elephants, they did not live in the deep moist tropical forest that were present along much of the West African coast in the 16th century,” she said. “They lived in mixed habitats, which is the type of habitat near which major West African trading posts were located.”
Prior to this analysis, the distribution of forest elephants in western Africa outside of tropical forest habitats was “attributed to the decimation of savanna elephants in West Africa in the 19th and 20th centuries,” said de Flamingh. The combination of DNA and isotopic evidence suggest that use of “savanna habitats by forest elephants in West Africa preceded the decimation of savanna elephants, and dates back to at least the 16th century,” she added.
Interestingly, the new research could be used to trace the source of illegal elephant ivory. The team will be adding the newly acquired DNA data to an open-access tool, called Loxodonta Localizer, developed at the University of Urbana-Champaign. This will allow officials to compare DNA extracted from poached elephant tusks with those kept in the online database, which stores DNA taken from elephants across Africa.
“The new data that we report in this study add substantially to the small body of information for West African elephants, and can aid in the sourcing of confiscated illegal ivory,” said de Flamingh. “Improving the ability to trace poached ivory can help guide optimal allocation of scarce law enforcement resources.”
It’s pretty amazing what this team managed to do with a batch of ivory tusks hidden beneath a beach in Namibia for nearly 500 years, but that’s the power of multidisciplinary research.