Modern hunter-gatherer societies, like those in southern Africa's Kalahari Desert, use ostrich eggshell beads to begin and maintain a relationship with other groups. The process is called hxaro, "kindling and cementing bonds within and between communities," according to a new study. The word hxaro has become synonymous with "beadwork" and "gifts."
So it stands to reason that the network exchanging them has a time-honored foundation. The researchers wanted to get to the heart of this social currency, finding out the time period and distances associated with them.
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The researchers established a range of strontium isotopes by piecing together how much was available in a given area based on strontium1 content in soil and vegetation samples. They also used museum specimens, like rodent tooth enamel.
Their analysis revealed that 80% of the beads could not have originated from the Lesotho highlands. The study published Monday in the journal Proceedings of the National Academy of Science.
"These ornaments were consistently coming from very long distances," said Brian Stewart, study author and University of Michigan paleolithic archaeologist."The oldest bead in our sample had the third highest strontium isotope value, so it is also one of the most exotic."
His analysis showed that they could not have come from closer than 202 miles away, and may have first been made by hunter-gatherers as far as 621 miles away.
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- 1. Old rock formations including granite are found to have more strontium than younger rocks like basalt. And when animals eat grass from around these rocks, the strontium becomes part of their tissues.
Brian A. Stewart, Yuchao Zhao, Peter J. Mitchell, Genevieve Dewar, James D. Gleason, Joel D. Blum, Ostrich eggshell bead strontium isotopes reveal persistent macroscale social networking across late Quaternary southern Africa. Proceedings of the National Academy of Sciences Mar 2020: 201921037.
Abstract: Hunter-gatherer exchange networks dampen subsistence and reproductive risks by building relationships of mutual support outside local groups that are underwritten by symbolic gift exchange. Hxaro, the system of delayed reciprocity between Ju/’hoãn individuals in southern Africa’s Kalahari Desert, is the best-known such example and the basis for most analogies and models of hunter-gatherer exchange in prehistory. However, its antiquity, drivers, and development remain unclear, as they do for long-distance exchanges among African foragers more broadly. Here we show through strontium isotope analyses of ostrich eggshell beads from highland Lesotho, and associated strontium isoscape development, that such practices stretch back into the late Middle Stone Age. We argue that these exchange items originated beyond the macroband from groups occupying the more water-stressed subcontinental interior. Tracking the emergence and persistence of macroscale, transbiome social networks helps illuminate the evolution of social strategies needed to thrive in stochastic environments, strategies that in our case study show persistence over more than 33,000 y.
Significance: Hunter-gatherers like the Ju/’hoãnsi (!Kung) San use exchange networks to dampen subsistence and reproductive risks, but almost nothing is known of how, when, and why such practices emerged. Strontium isotope analysis of one preferred San exchange item, ostrich eggshell beads, from highland Lesotho shows that since the late Middle Stone Age ∼33 ka, such networks connected ecologically complementary regions over minimal distances of several hundred kilometers. Rapidly changing environmental conditions during Marine Isotope Stage 3 (∼59 to 25 ka) likely placed a premium on developing effective means of mitigating subsistence and demographic risks, with ostrich eggshell beads providing a uniform medium of personal decoration and exchange highly suitable for binding together extended open social networks.
Keywords: ostrich eggshell beads, strontium isotope analysis, social networks, late Quaternary, and Southern Africa