The largest ever study of ostrich eggshell beads has identified a 50,000-year-old long-distance social network connecting human populations in eastern and southern Africa, that vanished with the onset of major shifts in the global climate.
Ostrich eggshell beads represent the earliest evidence of modern humans reworking the natural shape and size of resources for use as decorative ornaments. As different prehistoric groups produced their own styles of beads, researchers can trace population movement and cultural interactions depending on where the beads are discovered.
According to a study published today in Nature, Dr Jennifer Miller and Dr Yiming Wang from the Max Planck Institute for the Science of Human History collected data from more than 1500 ostrich eggshell beads recovered from 31 sites throughout southern and eastern Africa.
It took 10 years to assemble the data, which spans the last 50,000 years and has resulted in the creation of the largest ever database of ostrich eggshell beads.
Comparing their characteristics, such as their diameter and thickness, Miller and Wang found that between 50,000 and 33,000 years ago, populations in eastern and southern Africa (3,000km apart) were using virtually identical ostrich eggshell beads.
This indicates that a social network – the oldest yet discovered – existed between these two regions.
‘The result is surprising, but the pattern is clear,’ said Dr Wang. ‘Throughout the 50,000 years we examined, this is the only time period that the bead characteristics are the same.’
Additionally, the researchers realised that the disappearance of the network coincides with a major global climatic change in which the tropical rain belt shifted southward, increasing precipitation over the expanse connecting eastern and southern Africa. This would have flooded riverbanks, and perhaps created a barrier separating this cultural network.
‘Through this combination of paleoenvironmental proxies, climate models, and archaeological data, we can see the connection between climate change and cultural behavior,’ said Dr Wang. This is possibly the first direct evidence of such a link.
Dr Miller added: ‘We encourage other researchers to build upon this database, and continue exploring evidence for cultural connection in new regions.’