Humans of the Kalahari Desert Region Formed Social Networks

Ostrich eggshell beads were exchanged between ancient hunter-gatherers living in distant, ecologically diverse regions of southern Africa, including deserts and high mountains. (Image courtesy of Brian A. Stewart, Yuchao Zhao, and the University of Michigan Museum of Anthropological Archaeology/John Klausmeyer) via Smithssonian.com

By Megan Gannon. First published at Smithsonianmag.com.

Foragers today who live in southern Africa's Kalahari Desert know that a drought or war can threaten their community's survival. To mitigate these risks, they enter into partnerships with kin in other territories, both near and far, so that if they have a bad year, they can head to another area to gather water and food.

"It's a really good adaptation to a desert environment like the Kalahari, which has huge spatial and temporal variability in resource distribution," says Brian Stewart, an archaeologist at the University of Michigan. "It can be very rainy in one season and in the next absolutely dry, or it can be very rainy in your area and then 10 kilometers away, it's just nothing." According to new archaeological research led by Stewart, this kind of partnership—which acts as a kind of insurance against one side of the partnership having a down year—has been happening for at least 30,000 years old.

In the study, which was published today in the journal Proceedings of the National Academy of Sciences, Stewart and his colleagues examined ostrich eggshell beads found during archaeological excavations at two high elevation rock-shelters in Lesotho, a country enclaved within South Africa. Since the 1970s and 1980s, archaeologists have been finding finished beads made from ostrich eggshells at prehistoric campsites in the area, Stewart says, even though ostriches are notably absent from the region. Based on this fact, and on anthropologists' comparisons with the systems used by modern hunter-gatherers, scientists assumed the ostrich beads to be part of the foragers’ long-distance insurance partnerships. That is, people from many miles away brought the beads and traded them to cement the social ties needed to ensure cooperation when one group of people endured tough times.

"Because of how effective this system is at shoring up risk, it's been used by a lot of archaeologists as a blanket explanation for why people exchange stuff," Stewart says. But, he adds, this idea hadn't really been tested for the archaeological record.

To figure out where the beads from Lesotho were created, Stewart and his colleagues examined their strontium isotope levels. Earth’s crust is abundant with a slightly radioactive isotope of rubidium that, over time, decays into strontium. As a result, different rock formations have different strontium signatures, and local animals can acquire those unique signatures via food and water. In this way, researchers can figure out where a 30,000-year-old ostrich came from.

"Now with globalization and our food moving all over the place—we can eat avocados in December in Boston, for instance—our strontium signatures are all messed up," Stewart says. "In the past, they would have been more pure to where we're actually from."

The study showed that the majority of the beads from the Lesotho rock shelters were carved from the eggshells of ostriches that lived at least 60 miles (100 km) away. A few even came from about 190 miles (300 km) away, including the oldest bead, which was about 33,000 years old. "The really surprising thing was just how far they were coming in from, and how long that long distance behavior was going on," Stewart says.

Archaeologists have documented, in the Kalahari and elsewhere, the deep history of long-distance movements of utilitarian items such as stone tools and ochre pigment, which can be used as a sunscreen or a way to preserve hides. In East Africa, researchers have recorded instances of obsidian tools being carried more than 100 miles (160 km) as early as 200,000 years ago.

"When you have stone or ochre, you don't really know that this exchange is representing social ties," says Polly Wiessner, the anthropologist who first documented the exchange partnerships among the Ju/’hoãnsi people in the Kalahari Desert in the 1970s. "However, these beads are symbolic. This is one of our only sources for such early times to understand social relations."

Wiessner suspects that the closer-range ties—the ones around 60 miles—that Stewart and his colleagues found indeed represent people who pooled risk and shared resources. However, she says, it’s possible that the few examples of beads that came from further away could have been acquired through trade networks.

"Often at the edge of risk-sharing systems, feeder routes extend to bring in goods from other areas by trade or barter and so the recipient does not know people at the source," says Wiessner, who wasn't involved in Stewart’s study but reviewed it for the journal. "It doesn't mean people had face-to-face contact from that far away."

Wiessner points out that people living 30,000 years ago were anatomically modern humans, so she would expect them to have large social networks. Similarly, Lyn Wadley, an archaeologist with the University of the Witwatersrand in South Africa, says, "I think that gift exchange is likely to have a much earlier origin." Wadley, who has studied the social organization of Stone Age hunter-gatherers but wasn't involved in the new study, also found the results convincing.

The new study suggests that the exchange network would have spanned at least eight bioregions, from arid scrubland to subtropical coastal forests. Stewart and his colleagues speculate that the system may have arisen during a period of climate instability, when access to a diversity of resources would have been crucial.

"This is just another piece in the puzzle of the incredible flexibility of our species," Stewart says. "We are able to innovate technologies that just make us so good at adapting very quickly to different environmental scenarios."

Africa's Past Revealed in Journeys of Ostrich Eggshell Beads

First published at The Conversation by Elizabeth Sawchuk Postdoctoral Fellow and Research Assistant Professor of Anthropology, Stony Brook University (The State University of New York) and Jennifer Midori Miller, Postdoctoral Researcher, Max Planck Institute for the Science of Human History.

You can tell a lot about a person by the things they wear, and this has likely been true throughout human history. The earliest kind of decoration was probably ochre, which we know humans have used for at least 200,000 years.

By 75,000 years ago, people begin wearing beads. Since that time, ornaments and other symbols have been central to the way we express our identities and signal our relationships. In fact, this is probably one of the things that makes us human.

Ornament production really took off about 50,000 years ago, when we see the earliest standardised jewellery in the form of small disc beads made from ostrich eggshells. In Africa, ostrich eggshell beads are one of the most common type of archaeological artifacts, particularly from sites dated to the last 10,000 years. They are also found in smaller numbers throughout Asia where 12,000-year-old ostrich eggshell beads have been discovered in China.

Since ostrich eggshell bead jewellery is still produced today, this is one of the longest running cultural traditions in the world.

Photo by Tom Podmore on Unsplash. Modern-Day ostrich strolling along cape point, cape peninsula, cape town, south africa.

But what can these beads tell us about the ancient peoples who made and wore them?

In a recently published paper, we analysed 1,200 ostrich eggshell beads from 22 sites in southern Africa and eight sites in eastern Africa. Although beads are found at many African archaeological sites, they tend to be overlooked in research. Many of the bead measurements for this study were taken from decades-old, unstudied collections and are being reported for the first time. We believe that this research demonstrates the importance of studying existing museum collections and approaching old questions in new ways.

Our aim was to see how ostrich eggshell bead size has changed over the past 10,000 years. Bead size has become an informal way to estimate the age of archaeological sites in southern Africa. Yet beads overall have received relatively little attention compared to other types of artefacts and there is much we still don’t know. Our study increases the number of published bead measurements from less than 100 to over 1000, allowing us to study patterns on a larger scale and gain new perspectives on the African past.

Our findings provide important insights into how ancient peoples responded to change. Topics like migration and the economy dominate today’s new cycle. Yet ancient peoples also faced issues like climate change, cultural contact, and economic shifts. The things that people made and used, like ostrich eggshell beads, can help us understand the impacts of these changes on their lives.

Photo by Team Mfina on Unsplash https://unsplash.com/photos/n_MZ5snB8qk

Herders versus hunter-gatherers

Three decades ago, the archaeologist Leon Jacobson noticed a pattern in ostrich eggshell beads from Namibia. Those associated with hunter-gatherer sites tended to be smaller than those associated with herder sites. Since we know that herding entered southern Africa around 2000 years ago, Jacobson suggested that sites with beads larger than about 7.5mm might be younger than that.

Other studies confirmed the same pattern within the western part of southern Africa. Some researchers also argued that bead size might help distinguish which sites were used by herders versus hunter-gatherers. But this remains contested.

Until now, the idea that ostrich eggshell beads changed with the introduction of herding had only been tested in the southern part of Africa, and with a limited number of sites. We therefore decided to test this with a much larger dataset, and in other places like eastern Africa where herding also spread some 3000 years earlier.

Regional variations

At the southern African sites, we also found that larger beads appeared after 2,000 years ago. However, contrary to previous studies, our data show that these larger beads did not replace long-standing bead traditions. In fact, the vast majority of ostrich eggshell beads continued to be quite small. On the other hand, beads from the eastern African sites were highly variable in size and showed no change when herding entered that region around 5,000 years ago.

Ostrich eggshell beads in eastern and southern Africa seem to tell a different story about herding’s spread. Cattle, sheep and goats are not native to either of these regions and must have been introduced by contact with peoples living farther north.

In both places, groups also made ostrich eggshell beads before and after herding spread.

In eastern Africa, the lack of change in bead size could suggest that local hunter-gatherers adopted livestock, or that incoming herders possessed similar traditions and/or quickly adopted local styles.

In southern Africa, the appearance of larger beads around 2000 years ago suggests the introduction of livestock stimulated a change in bead traditions, or that new styles were introduced at the same time as sheep.

Yet in both places, local bead traditions remained dominant. Curiously, the larger beads in southern Africa fall within the range of eastern African beads, hinting at contact between these regions as suggested by other archaeological evidence and ancient DNA.

Our research findings suggest that the spread of herding into new areas did not lead to the replacement of local peoples and practices. Rather, people responded in more nuanced ways and maintained certain cultural traditions.

This research not only helps us understand the African past, but is important for considering how we as humans use culture to cope with the changes in our world.

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