Hunter-gatherers strung a social safety net across much of southern Africa starting at least 33,000 years ago, a new study suggests. And it was held together with ostrich eggshell beads.
Some of these carefully crafted beads — excavated at two high-altitude rock-shelters in the African nation of Lesotho — were found to have originated more than 100 kilometers away, while others came from more than 300 kilometers away, say anthropological archaeologist Brian Stewart of the University of Michigan in Ann Arbor and his colleagues. Ages of the beads span nearly the last 33,000 years, the scientists report March 9 in the Proceedings of the National Academy of Sciences.
Hunter-gatherers inhabiting inland desert or grassland regions probably started a regional exchange network toward the end of the Stone Age, somewhat akin to how many modern hunter-gatherer groups give gifts back and forth to foster cooperation, Stewart says. Ostriches lived in those dry, flat grasslands, but not at the rock-shelter sites. Inland residents could have made the beads from collected ostrich eggshells. The beads were probably then passed from one group of people to another over long distances, Stewart says. The findings indicate that this activity went on for tens of thousands of years longer than anyone previously has demonstrated for a system of cooperation-currying gift exchanges.
It’s “highly plausible” that ostrich eggshell beads were transported over long distances in ancient Africa, says archaeologist Nick Barton of the University of Oxford, who was not part of the new study. More work is needed to tell if inland hunter-gatherers perhaps obtained ostrich eggshells near southern Africa’s east coast, where seashells were also collected for bead making during the Stone Age. If so, bead distribution may have started near the east coast, Barton says.
Periodic food and water scarcity in the deserts and grasslands may have stimulated the founding of a bead exchange network, Stewart’s team proposes. Geological studies have indicated that sharp climate fluctuations between around 58,000 and 24,000 years ago caused ecological havoc in inland Africa, he says.
Beads may have been given as gifts to create a sense of indebtedness and unity across groups, thus damping down cultural differences between disparate hunter-gatherer populations. Or the exchange might have created goodwill or helped in recruiting culturally distinct groups into a kind of mutual aid society, Stewart suspects. Groups in resource-rich areas, such as highland Lesotho near the coast, could have sent food and other types of assistance through the network to inland people in need. But the beads’ exact function is unknown. Gifts given in exchange for ostrich eggshell beads were probably items that didn’t preserve over the millennia.
Ostrich eggshell beads date to as early as around 50,000 years ago in eastern and southern Africa. But well before that, perhaps 200,000 years ago or more, hunter-gatherers likely found other ways to form exchange networks in which groups came to each other’s aid, Stewart suspects. “What changed is that people got better at forming and maintaining these networks, hence the development of ostrich eggshell beads,” he says.
Stewart’s findings fit with a broader idea, supported by ancient DNA evidence, that different hunter-gatherer groups consisting mainly of in-laws and unrelated individuals have long maintained regional contacts that have benefits for all, says anthropologist Kim Hill of Arizona State University in Tempe, who did not participate in the new study (SN: 10/5/17). Organized trading and gift exchanges across groups foster widespread cooperation, a valuable outcome regardless of whether the climate is stable or volatile, Hill contends.
For that reason, he says, Stewart’s speculation about the ancient roots of exchange networks makes sense. “I suspect these practices began long before 33,000 years ago, and not just in southern Africa.”
Stewart’s team analyzed forms of the element strontium in 27 ostrich eggshell beads excavated at the two Lesotho rock-shelters, Sehonghong and Melikane. Signature ratios of different forms, or isotopes, of strontium reflect strontium concentrations in local soils and water. To track the origins of the rock-shelter beads, the scientists measured strontium values for plants, soil and small-mammal teeth in different parts of southern Africa.
Further chemical analyses are planned for the Lesotho rock-shelter beads as well as for ostrich eggshell beads previously excavated elsewhere in southern Africa.
The researchers can’t say whether Stone Age bead exchanges worked like the gift exchange system known as hxaro, practiced by some San hunter-gatherers today in southern Africa’s Kalahari Desert. In hxaro, two members of the same or different groups, some located 50 kilometers or more apart, exchange gifts to create a network in which people provide each other various forms of assistance. These groups, or bands, can range in size from an extended family to around 100 individuals. Ostrich eggshell beads are often included in hxaro gifts between bands, especially to assist in arranging marriages or to set up the expectation of receiving shelter during tough times.