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

Abstract

Humans evolved in a patchwork of semi-connected populations across Africa1,2; understanding when and how these groups connected is critical to interpreting our present-day biological and cultural diversity. Genetic analyses reveal that eastern and southern African lineages diverged sometime in the Pleistocene epoch, approximately 350–70 thousand years ago (ka)3,4; however, little is known about the exact timing of these interactions, the cultural context of these exchanges or the mechanisms that drove their separation. Here we compare ostrich eggshell bead variations between eastern and southern Africa to explore population dynamics over the past 50,000 years. We found that ostrich eggshell bead technology probably originated in eastern Africa and spread southward approximately 50–33 ka via a regional network. This connection breaks down approximately 33 ka, with populations remaining isolated until herders entered southern Africa after 2 ka. The timing of this disconnection broadly corresponds with the southward shift of the Intertropical Convergence Zone, which caused periodic flooding of the Zambezi River catchment (an area that connects eastern and southern Africa). This suggests that climate exerted some influence in shaping human social contact. Our study implies a later regional divergence than predicted by genetic analyses, identifies an approximately 3,000-kilometre stylistic connection and offers important new insights into the social dimension of ancient interactions.

Ostrich eggshell beads from Ga-Mohana Hill North Rockshelter, southern Kalahari, and the implications for understanding social networks during Marine Isotope Stage 2

“…Many sites we discuss in this review lack much of these data restricting our understanding of the role of OES and OES beads in the past. In this respect, we concur with Miller and Wang [ 14 ], Miller [ 10 ], Miller and Sawchuk [ 13 ], Collins et al [ 30 ], and Collins [ 9 ] in arguing for greater attention to OES and OES bead assemblages, and specifically for providing crucial (and fundamental) technological data for these assemblages. We now know the practice of culturing bodies with OES beads was widespread geographically across southern and eastern Africa and China during the Late Pleistocene.…”

“…Jacobson was the first to note differences in the sizes of OES beads between the archaeological assemblages of forager and pastoralists groups, where foragers generally manufactured smaller beads [ 12 ]. In recent years there has been more research interest in OES beads, with further studies examining the variation in bead size during the Holocene [ 13 ] and Late Pleistocene [ 14 ] across both eastern and southern Africa. Isotopic analyses of OES beads in Lesotho and the Maloti Drakensberg, showing that OES beads were traded across large distances (>300km) as far back as 33,000 years ago (ka) [ 5 ], while stylistic comparisons suggest social networks spanning eastern and southern Africa as far back as 55,000 years ago [ 14 ].…”

“…Research of OES beads in archaeological contexts generally focuses on identifying variation in bead style, specifically changes or differences in OES bead technological properties, such as shape and diameter, and using these differences as proxies for inferring stylistic differences between cultural groups [ 12 – 14 , 18 ]. More recently, isotopic analyses have also been used to track the movement of OES beads across the landscape [ 5 , 24 ], with the results informing our understanding of the nature and extent of past exchange networks.…”

Microstructural and crystallographic evolution of palaeognath (Aves) eggshells

“…Zooarchaeology (or anthrozoology) is an additional serendipitous field that can be benefited by thorough understandings of palaeognath eggshells. Palaeognath eggs were not only important food resource for hunter-gatherers (Oskam et al, 2011; Collins and Steele, 2017; Diehl et al, 2022) but were also used for cultural purposes such as ornaments or storage containers (Texier et al, 2010; Langley, 2018; Wilkins et al, 2021; Miller and Wang, 2022), thereby, they are common in archaeological sites. Because chronological and palaeoenvironmental information inscribed in palaeognath eggshells in archaeological sites are available through isotopic analyses (Sharp et al, 2019; Niespolo et al, 2020, 2021), detailed microstructural information for those eggshells may provide more colourful implications (e.g.…”

Phylogeography of Sub-Saharan Mitochondrial Lineages Outside Africa Highlights the Roles of the Holocene Climate Changes and the Atlantic Slave Trade

“…This may have been fuelled by the moister conditions following a major drought [ 15 , 16 ] and the possible arrival of novel uses of symbolic activities and technology associated with aspects of “modern” behaviour that took hold in southern African refugia ~130–75 ka [ 17 ]. This is suggested by major dispersals of L0 lineages from Southern to Eastern Africa occurring at this time [ 6 ] and may have led to the establishment of long-term networks between South and East Africa [ 18 ]. As a result of these expansions centred on Eastern Africa, L3 is today well represented across Africa, including in deep clades in Central and West Africa, and also encompasses all non-African mtDNA variation, following dispersals out of Eastern Africa into Eurasia that took place as part of the same process [ 16 , 19 ].…”