Prehistoric southern Africans were trading beads made of ostrich egg far and wide for tens of thousands of years, according to a new study published Monday in the U.S. Proceedings of the National Academy of Sciences.
Isotope analysis by scientists at the University of Michigan has demonstrated that eggshell beads made in the Karoo desert region of southern Africa “traveled” hundreds of kilometers from their site of origin, including to what is now Lesotho.
Some of the beads found in Lesotho could not have come from closer than 325 kilometers (200 miles), writes the team of archaeologist Brian Stewart and colleagues. Some may have been made as far as 1,000 kilometers away.
The team also suggests that the beads traveled during a time of climactic upheaval, about 59,000 to 25,000 years ago.
Ostriches aren’t fussy eaters, to say the least. These biggest of extant birds like to eat roots, leaves and seeds, but a hungry ostrich will eat anything including reptiles and rodents, if they can catch them. The isotopes the bird ingests in its meals become incorporated into its eggs, if it is female. And thus, isotopic analysis can help us know where the egg-layer lived.
It turns out that the egg-laying ostriches lived very far from where the eggshell beads were found some 33,000 years after their manufacture. The eggshell beads were found in Lesotho, but the ostrich who produced the egg that was turned into trinkets lived in the Karoo (in what is now South Africa).
Why might the beads have traveled such a long way? It’s hard to know. For one thing, we clearly know that prehistoric peoples, and their hominin predecessors, had mad wanderlust. There is even a theory that Homo sapiens prevailed over other early human species because of its sheer derring-do: it would boldly go where no hominin had gone before.
Stewart and his team postulate that the beads were manufactured at a time of climatic upheaval in Africa. In other words, possibly the prehistoric people would be boldly going to more survivable areas with more water, and possibly taking not only armaments with them but also beads as presents.
Outlandishly social animals
North Africa periodically underwent pluvial periods, when the Sahara would turn lush and verdant, and hippos and crocodiles would frisk in its bountiful waters and lakes. Some paleontologists even suspect the reason anatomically modern humans exited North Africa for Eurasia had to do with the Mousterian Pluvial period ending, turning the Sahara into the beautiful but barren wasteland we know and love today.
Others may have traveled from the aridifying North African lands to southern Africa, where precipitation also fluctuated with climatic changes. The beads under study were discovered in an area featuring mountain ranges and rivers.
Lesotho has the highest average elevation on the continent and would likely have been a formidable place for hunter-gatherers to live, Stewart says. But it is rich in water, which may have provided some relief from the ravages of aridification further north.
To this day, Africans make necklaces and adornments out of ostrich eggshells, so finding those in the archaeological record was not entirely surprising. Finding them in Lesotho was, though, because ostriches don’t typically live there. Mountain-climbers and river-forgers, they are not. Nor was any evidence found that the beads were made locally in Lesotho – and isotope analysis confirmed as much. Ergo, they were imported, and the team suspects they were brought as gifts.
The team calls the eggshell beads a “social currency.” And while they may not be forever like diamonds, eggshell beads do travel well.
“Humans are just outlandishly social animals, and that goes back to these deep forces that selected for maximizing information – information that would have been useful for living in a hunter-gatherer society 30,000 years ago and earlier,” says Stewart, assistant professor of anthropology and assistant curator of the University of Michigan Museum of Anthropological Archaeology.
Stone Age Facebook ‘likes’?
Stewart even postulates that the bead exchange basically acted like “Stone Age versions of Facebook or Twitter ‘likes,’ simultaneously affirming connections to exchange partners while alerting others to the status of those relationships.”
How did isotope analysis confirm that the beads were made far, far away? The team explains: When the radioactive element rubidium-87 decays, it produces strontium-87. So older rocks such as granite and gneiss have more strontium than younger rocks such as volcanic basalt. When animals forage from a landscape, these strontium isotopes are incorporated into their tissues.
Lesotho is in the middle of a bullseye-shaped geological formation called the Karoo Supergroup, which formed from fairly recent volcanic eruptions, the team says. Those eruptions built up the Lesotho highlands – but around that structure are much older sedimentary rocks.
The outermost ring of the formation ranges between 325 and 1,000 kilometers away from the Lesotho sites, and there you have the closest point at which the ostriches were grazing or hunting whatever they ate.
The baseline of strontium isotope ratios in each location was tested in samples of plants, soil and dead rodent teeth collected from across Lesotho and surrounding areas.
Lesotho is small. The upshot is that nearly 80 percent of the beads the researchers found in Lesotho could not have originated from ostriches living in highland Lesotho.
“These ornaments were consistently coming from very long distances,” Stewart said. “The oldest bead in our sample had the third highest strontium isotope value, so it is also one of the most exotic.”
Hunter-gatherers may have used beads to “buy” access to others’ resources when a region’s weather turned bad, the team suggests. Or maybe to buy marriage partners. Or maybe they were not exchanged per se, but simply handed down from wearer to next-generation wearer as they moved along. It’s hard to know 33,000 years after the event.
Modern people still make beads out of the hapless bird’s eggs, making this one of the longest-lived ornamental traditions in the world (if we leave wearing bones, teeth and claws as pendants out of it). Even Neanderthals would deck themselves out in beads, though they aren’t known to have ever lived in Africa, and their earliest beads – from about 115,000 years ago in Spain – were made of shells.
One argument has been whether ostrich bead sizes changed over the millennia, and in southern Africa particularly, with the development of herding as opposed to just hunting-gathering. Some feel that the advent of herding in Namibia around 2,000 years ago, for instance, led to the manufacture of bigger ostrich eggshell beads.
Larger beads did begin to appear about 2,000 years ago, but not uniformly: small beads remained the rule – and in any case, the jury’s still out.
Stewart’s co-authors include University of Michigan graduate student Yuchao Zhao, Peter Mitchell of the University of Oxford, Genevieve Dewar of the University of Toronto Scarborough, and UM's James Gleason and Joel Blum.
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