Shipwrecked ivory sheds new light on African forest elephants

The remains of the oldest known shipwreck in southern Africa, including ivory from more than 100 elephant tusks, have been analyzed in a new study from Cell Press. The researchers used advanced testing methods to trace the tusks back to many distinct herds that once roamed West Africa.

In 2008, a vessel known as the Bom Jesus was found in Namibia. The Portuguese trading vessel had gone missing in 1533 on a journey to India while transporting the elephant tusks, forty tons of gold and silver coins, and other cargo. 

An international team of experts in Namibia, South Africa, the United Kingdom, and the United States combined paleogenomic, isotopic, archeological, and historical analyses to determine the origin of the shipwrecked cargo. The findings are shedding new light on African elephants in both the past and present.

The researchers set out to identify the source of the elephant ivory, which was widely circulated in early Indian and Atlantic trading systems.

“Elephants live in female-led family groups, and they tend to stay in the same geographic area throughout their lives,” said study co-author Alida de Flamingh. “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 geo-referenced African elephants.” 

Study co-author Ashley Coutu explained that comparing the shipwreck ivory DNA to that of elephants with known origins across Africa made it possible to pinpoint the geographic region and species of elephant that matched the shipwreck ivory.

“In order to fully explore where these elephant tusks originated, we needed multiple lines of evidence. 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. Our conclusions were only possible with all of the pieces of our interdisciplinary puzzle fitting together,” said Coutu.

The experts conducted isotope analyses of 97 tusks, which revealed that the ivory had come from African forest elephants. Their mitochondrial DNA traced them to 17 or more herds from West Africa, as opposed to Central Africa.

This was a surprise, said study co-author Shadreck Chirikure, because the Portuguese had established trade with the Kongo Kingdom and communities along the Congo River by the 16th century. “The expectation was that the elephants would be from different regions, especially West and Central Africa.”

Four of the mitochondrial haplotypes represented by the tusks are still found today in modern elephants. The others may have been lost due to overhunting or habitat destruction, explained the study authors. The results of the genetic tests also indicate that the elephants lived in mixed forest habitat instead of residing deep in the rainforest.

“There had been some thinking that African forest elephants moved out into savanna habitats in the early 20th century, after almost all savanna elephants were eliminated in West Africa,” said co-author Alfred L. Roca. 

“Our study showed that this was not the case, because the African forest elephant lived in savanna habitats in the early 16th century, long before the decimation of savanna elephants by the ivory trade occurred.”

The new data can now be used to assist in tracing the source of confiscated illegal ivory, noted De Flamingh, and these findings are just the beginning in terms of what can be learned about elephants from studies of ivory.

“There is tremendous potential to analyze historic ivory from other shipwrecks, as well as from archaeological contexts and museum collections to understand the life histories of elephant populations, the skills and lifeways of the people who hunted and traded the ivory, as well as the many journeys of African ivory across the world,” said Coutu. “The revelation of these connections tell important global histories.”

The study is published in the journal Current Biology.

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By Chrissy Sexton, Earth.com Staff Writer