Stone point variability reveals spatial, chronological and environmental structuring of eastern African Middle Stone Age populations

ABSTRACT

Stone points are one of the key features used to define the African Middle Stone Age (MSA). Regional patterns in their shape and size through time have been thought to reflect inter-group interactions and networks of populations and are used to define cultural phases within the MSA. However, eastern Africa does not have distinctive and widely applied chrono-stratigraphic point variants that divide its MSA record, which is often described as being highly variable. This paper presents a metric and geometric morphometric analysis of eastern African MSA points and evaluates potential drivers of variation in them in relation to null models of isolation by distance, time and environment. Approximately half of the shape variance in our sample can be explained by spatial, temporal and environmental differences, as well as by size, indicating a degree of demographic continuity through sustained cultural transmission. A portion of the remaining variance likely represents stylistic differences between assemblages, which are often the subject of interest in archaeological studies. The highly variable nature of the eastern African MSA may reflect the region’s refugial positioning within the continent, with point technology a flexible adaptive system that was dynamically employed across Africa during the MSA depending on varying social and ecological contexts, resulting in the appearance of both ‘generic’ and ‘specific’ tool forms at particular times and places.

RÉSUMÉ

Les pointes de pierre sont l’une des caractéristiques-clé utilisées pour définir l’Âge de Pierre Moyen africain (Middle Stone Age, MSA). Il a été proposé que les distributions régionales dans les forme et les grandeurs au cours du temps reflètent les interactions entre groupes et les réseaux de populations, et ces distributions sont utilisées pour définir les phases culturelles au sein du MSA. Cependant, l’Afrique de l’Est ne possède pas de variantes chrono-stratigraphiques dans les pointes qui soient distinctives et largement appliquées et qui segmentent les données du MSA. Du reste ce registre du MSA est souvent décrit comme étant très variable. Cet article présente une analyse morphométrique métrique et géométrique des pointes MSA d’Afrique de l’Est, et évalue les facteurs potentiels de leur variation par rapport aux modèles nuls d’isolement en fonction de la distance, du temps et de l’environnement. À peu près la moitié de la variance de forme dans notre échantillon peut s’expliquer par des différences spatiales, temporelles et environnementales, ainsi que par la grandeur, indiquant un degré de continuité démographique à travers une transmission culturelle soutenue. Une partie de la variance restante représente probablement des différences stylistiques entre assemblages, qui sont souvent un objet d’intérêt pour les études archéologiques. La nature très variable du MSA est-africain peut refléter un positionnement de la région en tant que refuge au sein du continent. La technologie des pointes représenterait un système adaptif flexible qui fut utilisé de manière dynamique à travers l’Afrique pendant le MSA en fonction de divers contextes sociaux et écologiques, entraînant l’apparition de formes d’outils ‘génériques’ et ‘spécifiques’ à des moments et des lieux particuliers.

KEYWORDS:

• Middle Stone Age
• eastern Africa
• stone tool technology
• geometric morphometrics
• early Homo sapiens

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Correction

Acknowledgements

We should first like to thank our collaborators on this project: Sharon Manura and Simon Mboya of the National Museums of Kenya and Sahleselasie Melaku of the National Museum of Ethiopia. We should also like to acknowledge the site permit holders who allowed us access to the archaeological material and provided additional contextual information and references about the sites studied: Dr David Pleurdeau and Dr Zelalem Assefa (Porc-Epic and Goda Buticha), Dr John Shea (Omo Kibish), Prof. Stanley Ambrose and Prof. Charles Nelson (Prospect Farm) and Dr Nick Blegen and Prof. Christian Tryon (Kaputhurin Formation). Additionally, we thank Prof. Larry Barham, Dr Eleanor Scerri and Dr Manuel Will, as well as two anonymous reviewers, for their helpful comments. This project was supported by funding awarded to LT by the Arts and Humanities Research Council (North-West Consortium Doctoral Training Partnership; AH/R012792/1), the Leakey Foundation (Movement, interaction, and structure: modelling population networks and cultural diversity in the African Middle Stone Age), the Wenner Gren Foundation (Gr. 10157) and the Lithic Studies Society (Jacobi Bursary, 2020).

Correction Statement

This article was originally published with errors, which have now been corrected in the online version. Please see Correction (https://doi.org/10.1080/0067270X.2024.2316535)

Additional information

Notes on contributors

Lucy Timbrell

Lucy Timbrell is a Postdoctoral Research Fellow at the Max Planck Institute of Geoanthropology, Germany, and the Department of Archaeology, Classics and Egyptology, University of Liverpool, United Kingdom. She completed her PhD at the University of Liverpool in 2023 exploring population dynamics among Middle Stone Age populations in eastern Africa. She uses geometric morphometrics, eco-cultural niche modelling and GIS, among other quantitative approaches, to investigate the articulation of material culture and palaeoenvironments in both Africa and Europe.

Behailu Habte

Behailu Habte is a Curator of Prehistoric Collections and Archaeologist at the National Museum of Ethiopia in Addis Ababa, Ethiopia. He completed his PhD at the University of Toulouse-Jean Jaures, France on the lithic technology of the Later Stone Age in the Horn of Africa. He is a lithic technology specialist, with interests in early human technical behaviour, subsistence economy and land use patterns in eastern Africa.

Yosef Tefera

Yosef Tefera is a Curator of Prehistoric Collections and Archaeologist at the National Museum of Ethiopia in Addis Ababa, Ethiopia. He completed his studies at Addis Ababa University and has interests in lithic technological behaviour during the Middle and Later Stone Ages in eastern Africa.

Christine Maroma

Christine Maroma is a Research Technologist in the Department of Archaeology in the National Museums of Kenya in Nairobi, Kenya. She is an expert on lithic technology and the archaeology of eastern Africa.

Emmanuel Ndiema

Emmanuel Ndiema is the Head of Archaeology at the National Museums of Kenya in Nairobi, Kenya. He is also a Research Associate in the Department of Archaeology at the Max Planck Institute of Geoanthropology in Germany. He completed his PhD at Rutgers University in New Jersey in the United States of America in 2011 exploring mobility and subsistence patterns among Mid-Holocene pastoralists in northern Kenya. His research investigates cultural responses to climatic variability, and he has been involved with many projects focused on the archaeology of eastern Africa, ranging from the Middle Pleistocene to the Holocene.

Kimberly Plomp

Kimberly Plomp is a bioarchaeologist and Faculty Member in the School of Archaeology at the University of the Philippines Diliman, Philippines. She completed her PhD at Durham University in the United Kingdom in 2013 quantifying palaeopathology using geometric morphometrics. She uses geometric morphometrics to investigate skeletal variation of both human and non-human primates.

James Blinkhorn

James Blinkhorn is a Senior Researcher in the Human Palaeosystems Group at the Max Planck Institute of Geoanthropology, Germany. He is also an Affiliated Scientist in the Department of Geography, Royal Holloway, University of London, United Kingdom. His research focuses on human-environment interactions and stone tool analyses, using spatial and computational methods to examine relationships between behavioural innovation, biological evolution, and environmental change.

Matt Grove

Matt Grove is a Professor in Evolutionary Anthropology in the Department of Archaeology, Classics and Egyptology at the University of Liverpool. His research interests in the Middle Stone Age of Eastern Africa, the effects of palaeoclimatic change and variability on hominin evolution and dispersal and developing new quantitative and computational methods for studying the archaeological record.