Shipwreck Discovery Reveals Treasure Trove of Elephant History
In the sixteenth century, the world was very different from the world we know today. Portugal was busy building its world trade and colonial empire, and ivory played an important role in commercial trading. When a sea route to India around Africa was found in 1498, Portuguese trade grew rapidly, with larger fleets being sent each year on faster routes. The Bom Jesus (“Good Jesus”) was one such ship, owned by one of Europe’s wealthiest merchants. In the year 1533, the Bom Jesus left Lisbon burdened with goods to trade but never arrived, disappearing somewhere off the African coast. The ship’s fate was unknown until more than 400 years later, when a diamond mining operation in Oranjemund, Namibia discovered its wreck in 2008. The shipwreck’s remarkably well-preserved, forty-ton cargo included more than 100 tusks from African forest elephants (Loxodonta cyclotis), providing researchers with a treasure trove of information about their historical range, diversity, and habitat.
As an international team of researchers found, DNA analysis was the key to unlocking the important history contained within the tusks. After using nuclear DNA to identify the tusks as belonging to forest elephants rather than savannah elephants, the researchers used mitochondrial DNA to trace the tusks back to 17 family lineages in West Africa. Mitochondrial DNA is passed down from mother to offspring; since elephants live in matriarchal groups that are relatively restricted to certain regions, the tusks’ mitochondrial DNA was used to pinpoint the origins of the tusks to distinct herds. Only four of these 17 lineages can still be found in Africa; the researchers attributed this significant decline in genetic diversity to habitat destruction and the ivory trade, which have reduced the historic elephant range in West Africa by at least 93 percent.
The ratios of stable carbon and nitrogen isotopes in the tusks were also an important clue as to their geographic origins. Carbon isotope ratios are influenced by an elephant’s diet, while nitrogen isotope ratios are indicators of soil moisture content. An analysis of both indicates that these forest elephants lived in mixed habitats, moving from woodland to savannah based on the season. The current distribution of forest elephants outside of rainforests has been previously attributed to the decrease in savannah elephant populations in the nineteenth and twentieth centuries, with the idea that forest elephants moved into their territories. However, these results suggest that L. cyclotis has been calling the savannah home for far longer — even as long ago as the sixteenth century. This study may provide further support for the existence of forest and savannah elephants as separate species; L. cyclotis was only officially recognized by the IUCN as a separate species this year (March 2021), although most scientists have made this distinction since 2013.
The greater insight into the historic ecology of forest elephants provided by this archaeological discovery can help inform the future of conservation research and planning. The decline in genetic diversity among forest elephants shown by this study is especially troubling because it makes the species more vulnerable to extinction. Now, researchers hope to use the data collected to build a more comprehensive timeline of forest elephant decline and the impact of the global ivory trade across generations. The ivory DNA sequences produced for this study are a valuable addition to the limited body of data on West African elephant genetics, and can be used to help verify the origins of poached ivory today. In addition, the researchers hope that their study’s pioneering interdisciplinary approach and combination of DNA and isotope analysis can be used to help reveal the histories hidden in museum ivory collections around the globe. This shipwreck has already revealed so much about forest elephant history, and we may have only scratched the surface of the treasure trove it holds.
References:
De Flamingh, A., Coutu, A., Sealy, J., Shadreck, C., Bastos, A.D.S., Libanda-Mubusisi, N.M., Malhi, R.S., & Roca, A.L. (2020) Sourcing Elephant Ivory from a Sixteenth-Century Portuguese Shipwreck. Current Biology, 31(3). Retrieved from https://www.cell.com/current-biology/fulltext/S0960-9822(20)31663-8
Gill, V. (2020, December 17). Ivory: Elephant decline revealed by shipwreck cargo. Retrieved from https://www.bbc.com/news/science-environment-55340975
Hart, J., Gobush, K., Maisels, F., Wasser, S., Okita-Ouma, B., & Slotow, R. (2021). African forest and savannah elephants treated as separate species. Oryx, 55(2), 170–171. doi:10.1017/S0030605320001386. Retrieved from https://www.cambridge.org/core/journals/oryx/article/african-forest-and-savannah-elephants-treated-as-separate-species/82D0F321A09B7F72D042B5B881D71484.
Werz, B. E. J. S. (2010). Sub-Saharan Africa’s Oldest Shipwreck: Historical-Archaeological Research of an Early Modern-Era Portuguese Merchantman on the Namibian Coast. The Mariner’s Mirror, 96(4), 430–442. Retrieved from https://www.tandfonline.com/doi/abs/10.1080/00253359.2010.10657159
Yates, D. (2021, January 13). Study tracks elephant tusks from 16th Century shipwreck. Retrieved from https://las.illinois.edu/news/2021-01-13/study-tracks-elephant-tusks-16th-century-shipwreck
