Strontium isotope analysis tracks prehistoric ostrich eggshell bead exchange in southern Africa

A recent study by archaeologist Prof. Peter Mitchell and his colleagues published in Azania: Archaeological Research in Africa examines how ostrich eggshell (OES) beads moved across southeast southern African landscapes during the Pleistocene and Holocene.

Their research found that hunter-gatherers living in the Lesotho highlands maintained exchange networks, which enabled them to acquire OES beads from hundreds of kilometers away. This challenges previous assumptions that OES beads were introduced to southern Africa and their exchange networks were only maintained from East Africa until their disruption and virtual ‘disappearance’ from the archaeological record between ~33–19kya.

OES beads are among the most common forms of jewelry found in pre-colonial southern Africa, having been found in contexts up to >50,000 years ago. The raw material from which they are made is abundant, durable, and cost-effective, especially compared to other raw materials such as estuarine or marine mollusks.

To the hunter-gatherer communities who made OES beads, ostriches played an important spiritual and social role in the hunter-gatherer communities who made them. In some hunter-gatherer groups, for example, it was believed that the ostrich created all humans, provided them with the knowledge of fire (and metaphorically sex), and once ruled over all the animals.

It possessed powers of healing and resurrection, two particularly important concepts in many hunter-gatherer groups who believed in order to enter trance (an altered state of mind) to heal those in their community, they needed to metaphorically ‘die’ to enter the spirit world.

Similarly, it was believed objects made from ostriches or OES would be imbued with the same attributes as the living animal. As such, arrow points made from ostrich bone would have the bird’s strength, speed, and stamina. Additionally, OES beads had healing powers and thus would play an important part in healing/trance dances, where they were worn by shamans and served to show the spirits the inherent humanness and beauty of the shaman.

However, OES beads were also thought to contain supernatural potency (power), which could prove dangerous, and thus, OES beads would be removed during first-time childbirth or when a child fell ill.

Given the deep spiritual significance of OES beads, they were central to the hxaro exchange system among the Ju/hoãnsi (!Kung) people—a delayed gift exchange network where individuals maintained 10 to 16 exchange partners, facilitating resource sharing and marriage arrangements across 100km distances or more, with ‘hxaro’ itself translating to ‘ostrich eggshell beadwork.’

Previous research into OES bead exchange networks claimed that the varying sizes of OES beads indicated that OES-making was introduced to southern Africa from East Africa. This exchange network was maintained until the flooding of the Zambezi and various droughts in Eastern Africa disrupted exchange networks, resulting in a virtual disappearance of OES beads in southern African sites between ~33-19kya.

However, Prof. Mitchell and his team point out flaws with this research, providing evidence and pointing out that not only is OES size more dependent on the intended use of the bead than its link to distinct communities, but that the previous research failed to account for critical factors like excavation mesh sizes and pH effects on bead preservation, while also overlooking several sites with documented OES beads and preforms (unfinished beads) during the supposed period of disappearance.

According to Prof. Mitchell, his interest in OES bead networks was sparked by the recovery of OES beads in an area in Lesotho where the bird does not naturally occur, “The interest arose from discovering OES beads in highland Lesotho, an ostrich-free area with no on-site evidence of bead-making, specifically at Sehonghong in 1992.”

Prof. Mitchell and his colleagues argue that bead measurements alone cannot prove exchange networks and that researchers need multiple lines of evidence to make such claims.

Thus, his research and that of his colleagues focused on various lines of evidence to determine the origin of OES beads from two archaeological sites in the Lesotho highlands, namely Melikane (<3300BP) and Sehonghong (~32kya to <1300BP), including ethnographic and historical accounts, archaeological evidence, and isotope analysis.

Both sites are found within the wider area of the Maloti-Drakensberg Mountains, which includes Lesotho, KwaZulu-Natal Province, and Eastern Cape Province (South Africa), as well as the eastern half of the Eastern Cape and much of KwaZulu-Natal.

This large area was neither historically nor archaeologically home to ostriches, with neither ostrich bone nor unmodified eggshells recovered from these regions. Additionally, the rock art in the area does not depict a single ostrich. These factors all indicate that OES beads would have had to have been imported.

The researchers used 27 OES beads, 16 from Sehonghong and 11 from Melikane. Using strontium isotopes, which can geolocate fauna, flora, and shells, they were able to determine the beads’ origin.

The results indicated that all beads originated from non-local sources, manufactured between 109 and 164km away, with three OES beads traveling up to 325km. The research demonstrates that OES beads circulated through regional networks spanning hundreds of kilometers within Southern Africa, contrasting with previous studies that used bead size alone to suggest extensive 2,700km trade routes between East and Southern Africa.

The researchers hope to extend future work to a much larger sample, including samples from a wider region and broader timeframe.

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