A study of 30 metal objects from Iron Age sites in eastern-central Botswana has found evidence of long-distance copper exchange across southern Africa, while the tin used to make bronze came from a single known source in South Africa.
The research examined material from Bosutswe, Khubu la Dintša and Lose, settlements associated with elite Lose-style pottery. The sites stood near river headwaters that drain toward the Limpopo and Indian Ocean, locations the researchers describe as important crossroads for east-west movement.
Bosutswe provided the clearest evidence of widely distributed copper. Lead-isotope and chemical analysis linked its copper to several mining areas, including the Copperbelt on the Congo-Zambia border, Copper Queen in Zimbabwe, and Musina, Phalaborwa and Rooiberg in South Africa. The objects also included copper associated with Botswana’s Selebi Phikwe and Dukwe deposits. Dukwe is just over 140 kilometers from Bosutswe, while some of the other sources were hundreds of kilometers away and, in one case, more than 950 kilometers distant.
This pattern differs from the evidence at some other regional sites. Mapungubwe, for example, obtained most of its copper from Phalaborwa, according to the study. At Bosutswe, the variety of sources indicates a more complex supply network, although the researchers said the available evidence does not identify how the metal was transported or exchanged.
Tin showed a much more consistent pattern. Every bronze object analyzed was compatible with tin from the Rooiberg valley in South Africa, about 360 kilometers from Bosutswe. Rooiberg is described as the only tin field in the region with evidence of pre-colonial mining.
Because the bronze objects combined Rooiberg tin with copper from different sources, the researchers argue that bronze was probably made at Bosutswe rather than traded there as finished material. The objects contained varying amounts of tin, producing colors ranging from red and salmon pink to golden yellow. The study interprets this variation as an expanded color range for elite ornaments, rather than evidence of attempts to imitate gold.
Bosutswe began as a cattle post in the seventh century, developed into a trade center, and was abandoned in the 17th century. Bronze appeared there around the 13th century. The findings, published in Azania: Archaeological Research in Africa, add metal production and exchange to evidence of the settlement’s connections with distant regions.
