Bosutswe Site Sourced Copper from Across Southern Africa

A new chemical analysis of 30 metal artifacts shows the Iron Age settlement of Bosutswe in Botswana was a major trade hub that sourced copper from mines scattered across southern Africa. The study, led by archaeologist Jay Stephens of New York University and published in Azania: Archaeological Research in Africa, traced materials to locations over 950 kilometers away, challenging previous views of the region as a peripheral backwater.

A Trade Hub on the Kalahari's Edge

The sites of Bosutswe, Khubu la Dintša, and Lose are Iron Age settlements located near river headwaters draining toward the Indian Ocean. This position made them ideal crossroads for trade. Bosutswe began as a cattle post in the 7th century before evolving into a significant center. It imported glass beads from Asia, cowrie shells from the coast, and possessed a gold spiral. Stephens states these were complex societies with far-reaching connections. "They also constructed impressive architectural features which still exist today," he added, noting many modern southern Africans are their descendants.

Tracing Copper's Geological Fingerprint

Researchers have detailed knowledge of imports from the Swahili coast but little about internal regional trade, especially in metals. Tracing gold and iron is nearly impossible due to abundance and reuse. Copper and tin, however, are scarcer and carry unique lead isotope signatures that act as geological fingerprints. Over two decades, the team sampled artifacts from the three sites to match these fingerprints to known mines.

The results were surprising. While other regional centers like Mapungubwe sourced copper mainly from Phalaborwa, Bosutswe's copper came from a wide array of distant sources.

Curiously, only two local Botswana copper mines, Selebi Phikwe and Dukwe, appear in the artifacts. "It's a really fascinating puzzle," Stephens said. "These massive distances seem to fit an exciting trend that we are only starting to understand." He describes this as evidence of trade networks maintained across vast distances for centuries. The specific mechanisms of trade remain unclear. "Bosutswe presents a more complicated case study, as we have no smoking gun to point towards one mechanism over another," Stephens explained.

A Single Source for All Tin

In contrast to the diverse copper sources, every analyzed bronze object pointed to a single origin for its tin: the Rooiberg valley in South Africa, located 360 kilometers away. This is the only known pre-colonial tin field in the region. The finding suggests bronze was not imported as a finished product but was manufactured locally at Bosutswe by mixing imported tin with whatever copper was available.

The tin content in these bronzes varied widely, creating a spectrum of colors from red to salmon pink and golden yellow. According to the researchers, this was not failed attempts to imitate gold but a deliberate expansion of the color palette for elite jewelry. "These are often put in contrast together when worn as bangles or other items of jewelry, sometimes even in the same object," Stephens noted.

Bronze first appeared at Bosutswe around the 13th century, contemporaneous with its appearance at Mapungubwe. However, while the Mapungubwe kingdom lasted only about a century, Bosutswe endured until its abandonment in the 17th century. Stephens concludes, "The degree of interconnection at Bosutswe is astonishing." The study's findings are based on isotopic and chemical evidence detailed in the 2026 journal article.