Ostrich eggshell beads reveal 50,000-year-old social network across Africa


Digital microscope images of archaeological ostrich eggshell beads. Credit: Jennifer Miller

Humans are social creatures, but little is known about when, how, and why different populations connected in the past. Answering these questions is crucial in interpreting the biological and cultural diversity that we see in human populations today. DNA is a powerful tool for studying genetic interactions between populations, but it does not allow us to tackle cultural exchanges within these ancient encounters. Today, scientists at the Max Planck Institute for the Science of Human History turned to an unexpected source of information, ostrich eggshell beads, to shed light on ancient networks. social. In a new study published in Nature, researchers Drs. Jennifer Miller and Yiming Wang report 50,000 years of population connection and isolation, driven by changing precipitation, in southern and eastern Africa.

Ostrich eggshell beads: a window to the past

Ostrich Eggshell Beads (OES) are ideal artifacts for understanding ancient social relationships. They are the oldest fully manufactured ornaments in the world, which means that instead of relying on the size or natural shape of an item, humans have completely transformed seashells to produce pearls. This extensive formatting creates plenty of possibilities for styling variations. Because different cultures produced beads of different styles, prehistoric props offer researchers a way to trace cultural connections.

“It’s like following a breadcrumb trail,” says Miller, lead author of the study. “Pearls are clues, scattered across time and space, just waiting to be noticed.”

To look for signs of connectivity between populations, Miller and Wang assembled the largest database ever on ostrich eggshell pearls. It includes data from more than 1,500 individual beads discovered at 31 sites across southern and eastern Africa, spanning the past 50,000 years. Collecting this data was an extremely slow process that took over a decade.

Ostrich eggshell beads reveal 50,000-year-old social network across Africa

A string of modern East African ostrich eggshell beads. Credit: Hans Sell

Climate change and social media in the Stone Age

By comparing characteristics of OES beads, such as overall diameter, opening diameter, and shell thickness, Miller and Wang found that between 50,000 and 33,000 years ago, populations of East and Southern Africa used almost identical OES beads. The finding suggests a long-distance social network spanning more than 3,000 km once people connect in the two regions.

“The result is surprising, but the pattern is clear,” says Wang, co-author of the study. “In the 50,000 years that we have looked at, this is the only period where the characteristics of the logs are the same.”

This east-south connection, 50 to 33,000 years ago, is the oldest social network ever to be identified and coincides with a particularly humid period in East Africa. However, signs of the regional network disappeared 33,000 years ago, possibly triggered by a major change in global climates. Around the same time as the social network collapsed, East Africa experienced a dramatic reduction in rainfall as the tropical rain belt moved south. This increased rains in the vast area connecting East and Southern Africa (the Zambezi River watershed), periodically inundating the riverbanks and possibly creating a geographic barrier that disrupted regional social networks.

“Through this combination of paleoenvironmental proxies, climate models and archaeological data, we can see the link between climate change and cultural behavior,” says Wang.

Ostrich eggshell beads reveal 50,000-year-old social network across Africa

Oldupai Gorge in Tanzania, an important site in studies of human evolution, experiences drying out and shorter, more erratic rains. Credit: Yiming Wang

Weaving a story with pearls

Together, the results of this work document a 50,000-year history of human relationships and the dramatic climate changes that have separated people. The data even provide new insight into varying social strategies between East and Southern Africa by documenting different trajectories of log use over time. These regional responses highlight the flexibility of human behavior and show that there are several paths to success for our species.

“These tiny pearls have the power to reveal great stories about our past,” says Miller. “We encourage other researchers to build on this database and continue to explore evidence of a cultural connection in new regions.”


Ostrich eggshell beads reveal 10,000 years of cultural interaction across Africa


More information:
Jennifer Miller, Ostrich Eggshell Beads Reveal 50,000-Year-Old Social Network in Africa, Nature (2021). DOI: 10.1038 / s41586-021-04227-2. www.nature.com/articles/s41586-021-04227-2

Provided by the company Max Planck

Quote: Ostrich Eggshell Beads Reveal 50,000-Year-Old Social Network Across Africa (2021, December 20) Retrieved December 20, 2021 from https://phys.org/news/2021-12 -ostrich-eggshell-beads-reveal-year-old .html

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