Ostrich eggshell bead diameter in the Holocene: Regional variation with the spread of herding in eastern and southern Africa
Bibliographic record
Abstract
Despite their ubiquity in Holocene African archaeological assemblages, ostrich eggshell (OES) beads are rarely studied in detail. An exception is in southern Africa, where there is a proposed relationship between OES bead diameter and the arrival of herding ~2000 years before present. In 1987, Leon Jacobson first observed that beads from forager sites in Namibia tended to be smaller than those associated with herder sites. Studies examining bead size around the Western Cape have generally confirmed Jacobson's findings, though the driving forces of the diameter change remain unknown. Since this time, diameter has become an informal way of distinguishing forager and herder assemblages in southern Africa, but no large-scale studies of OES bead variation have been undertaken. Here we present an expanded analysis of Holocene OES bead diameters from southern, and for the first time, eastern Africa. Results reveal distinct patterns in OES bead size over time, reflecting different local dynamics associated with the spread of herding. In southern Africa, OES diameters display low variability and smaller absolute size through time. While larger beads begin to appear <2000 years ago, most beads in our study remained smaller. In contrast, eastern African OES bead diameters are consistently larger over the last 10,000 years and show no appreciable size change with the introduction of herding. Notably, larger beads thought to be associated with herders in southern Africa fall within the range of eastern African beads, indicating a potential connection between these regions in the Late Holocene consistent with genetic findings. Regional differences in bead size are subtle, on the order of millimeters, yet offer a potentially important line of evidence for investigating the spread of herding in sub-Saharan Africa. In order to understand the meaning of these changes, we encourage additional studies of OES bead assemblages and urge researchers to report individual bead diameters, rather than averages by level.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".