A decade-long study of more than 1,500 beads made from ostrich eggshells and found across Africa has revealed a 50,000-year-old social network, archaeologists say.
The donut-shaped beads are among the earliest kinds of personal adornment found in the archaeological record — and some traditional, hunter-gatherer groups in southern Africa still make and use the beads today.
“People made them to communicate symbolic messages, the way that today we might wear a wedding ring, to indicate something about social status, wealth or position in society,” said Jennifer Miller, a postdoctoral researcher in the department of archaeology at the Max Planck Institute for the Science of Human History, in Jena, Germany.
They studied 1,516 beads (1,238 of which were described for the first time) that originated from 31 different sites across southern and eastern Africa and spanned the last 50,000 years.
Comparing the different characteristics of the beads — the diameter and thickness — they found that between 33,000 and 50,000 years ago, people at sites across southern and eastern Africa — spanning a distance of more than 3,000 kilometers (1,864 miles) — were using almost identical beads.
“It’s kind of mind-boggling that these people, who lived 40,000 to 50,000 years ago, would have had some kind of social network that spread over such a long distance.”
The oldest beads come from East Africa, the study found, and likely spread south across the continent from there. The authors described it as the oldest social network ever identified and the furthest Stone Age “stylistic connection” ever documented.
While it’s possible the beads could have been directly exchanged in some way, Miller thought more likely it was the knowledge of how to make them that was exchanged.
“Based on what we’re seeing, it looks like a single origin that spread out from that one region, sharing the same style,” she said. “Possibly people would have seen this new thing that people were were wearing or making and thought, ‘Oh, that’s so cool.’ And then mimicked it,” Miller said.
“And so in that way, rather than obtaining these beads directly, it might have been more of a copying the cool new thing.”
However, this network — as represented by the similar style of beads — appeared to have broken down by 33,000 years ago.
After this point in time, bead use appeared to disappear in southern Africa, while continuing in East Africa. Starting about 19,000 years ago, beads re-emerged in southern Africa and in much larger numbers and in a different style.
The two populations, once seemingly intertwined, remained isolated until livestock herding was introduced into southern Africa approximately 2,000 years ago, the study said.
So what changed? The authors believe it was the climate. Around 33,000 years ago, a meteorological phenomenon known as the Intertropical Convergence Zone moved southward, which caused flooding of the Zambezi River catchment. This area connects eastern and southern Africa, and the flooding could have acted as a barrier to human interaction, according to study co-author Yiming Wang. Wang is a post-doctoral researcher in the department of archaeology at the Max Planck Institute.
In southern Africa, it’s possible that populations then dispersed into smaller groups that had less need to make beads, Miller said. Or it could be that not enough people knew about the tradition, or the skills behind it, for it to continue for some time.
“Because beads of this type are so labor intensive, they’re really only beneficial if you have a large enough social network to need symbolic communication. Living in smaller groups (for example with immediate/extended family), symbolic communication can be more costly than beneficial — these convey messages that they would already know through other means,” Miller explained.
The paper makes a “strong case” for the climate theory, but more research — such identifying the source of the ostrich eggs using geochemistry and tracking their movement across the continent — would test the researchers’ findings, said Benjamin Collins, an anthropologist at the University of Manitoba, and Amy Hatton, a researcher at the Max Planck Institute for Chemical Ecology, in a commentary published alongside the paper. They were not involved in the study.