The environmental context of the Middle-to-Late Stone Age Transition in eastern Africa: seasonality as a key factor
This article has been Reviewed by the following groups
Discuss this preprint
Start a discussion What are Sciety discussions?Listed in
- Evaluated articles (Peer Community in Archaeology)
Abstract
In the transition between the Middle Stone Age (MSA) and the Late Stone Age (LSA) in eastern Africa, the archaeological record shows a gradual and asynchronous decline in MSA features and an increase in LSA characteristics. A link between this pattern and climatic variations has not yet been tested in the region using lithic attribute analysis.
To investigate that, we integrated technological data of blades and bladelets from eastern African contexts (Marine Isotope Stages 5–1) with large-scale paleoclimatic reconstructions. A principal component analysis (PCA) finds the first component (reflecting artifacts’ dimensions) significantly correlating with time. This highlights a progressive reduction in size over time, a trend that has already been suggested for the MSA-LSA transition. The second principal component reflects artifact shape and shows a significant correlation with the marked aridity of the dry season (a common proxy for seasonality in tropical regions), with higher specialization observed in more humid areas.
Based on this, we propose a new model where more variable blades reflect greater versatility in foraging strategies as adaptation to environments that become more challenging during part of the year. On the other hand, when it rains more during the dry season and differences through the year are milder, a more specialized toolkit with thinner, longer elements would emerge from refining and adapting to uniform and predictable situations and challenges.
Article activity feed
-
I am happy that the authors have sufficiently addressed all of my prior concerns and comments. I recommend the pre-print be published.
-
The reasons underlying technical and cultural transitions are often multiple and complex. Our understanding of these processes is inevitably constrained by the availability and quality of the data. The paper by Fusco et al. (2026) addresses one of the possible drivers of this transition: climate. The study successfully argues that the increased production of blades and bladelets characterizing the Late Stone Age (LSA) reflects a gradual process. It further proposes that more slender and thinner blades and bladelets were favoured in relatively homogeneous environments with predictable resource availability throughout the year, whereas more seasonally variable environments may have favoured shorter and thicker forms due to their greater versatility.
To support this argument, the authors integrate lithic technological attributes with …The reasons underlying technical and cultural transitions are often multiple and complex. Our understanding of these processes is inevitably constrained by the availability and quality of the data. The paper by Fusco et al. (2026) addresses one of the possible drivers of this transition: climate. The study successfully argues that the increased production of blades and bladelets characterizing the Late Stone Age (LSA) reflects a gradual process. It further proposes that more slender and thinner blades and bladelets were favoured in relatively homogeneous environments with predictable resource availability throughout the year, whereas more seasonally variable environments may have favoured shorter and thicker forms due to their greater versatility.
To support this argument, the authors integrate lithic technological attributes with paleoclimatic data. They examine several variables - maximum length, maximum width, maximum thickness, elongation index, and flattening index - measured on blade and bladelet assemblages from five Eastern African sites spanning the Middle Stone Age (MSA) and LSA. They first employ PCA to assess differences between MSA and LSA assemblages, identifying clear trends: a progressive reduction in size and marked morphological variability, with MSA assemblages characterized by shorter and thicker blanks and LSA assemblages by thinner and more elongated forms.
After identifying these trends, the authors explore several potential explanatory factors, including raw material selection and paleoclimate. Their analysis indicates no meaningful relationship between raw material variability and the observed technological patterns, whereas paleoclimatic variables show stronger correlations.
To test the relationship between morphological reduction and climatic conditions, the authors extract paleoclimatic data from the pastclim package (Beyer et al. 2020; Krapp et al. 2021; Leonardi et al. 2023). This package enables the download and manipulation of paleoclimatic datasets, including one covering the last 120,000 years (Beyer et al. 2020) and another extending back 800,000 years (Krapp et al. 2021). These datasets include 17 annual bioclimatic variables; 4 and 6 monthly bioclimatic variables, respectively; annual net primary productivity (NPP); leaf area index; land masks; ice sheet reconstructions; and biome reconstructions representing natural vegetation types (Leonardi et al. 2023, Box 1). All variables are bias-corrected and downscaled to a spatial resolution of 0.5° × 0.5°.
From this range of variables, the authors select mean annual temperature (bio01), total annual precipitation (bio12), net primary productivity (NPP), and precipitation of the driest season (bio17). These variables are integrated with the archaeological dataset while explicitly addressing methodological challenges, including chronological uncertainty, differences in excavation and documentation protocols among sites, sample size variability, and other potential limitations arising from the aggregation of legacy datasets.
All these aspects were carefully considered, and the manuscript, following substantial revision, now provides a more detailed and explicit account of the methodological framework and adopts a cautious and balanced approach in its interpretation of behavioural implications. In its current form, the paper has strong potential to serve as a key reference for future research on the interactions between climate variability and technological dynamics in prehistoric Africa. To further demonstrate a clear commitment to data transparency, the authors have uploaded the data and code required to reproduce the analyses.References
Beyer, R.M., Krapp, M. & Manica, A., 2020. High-resolution terrestrial climate, bioclimate and vegetation for the last 120,000 years. Sci Data 7, 236. https://doi.org/10.1038/s41597-020-0552-1
Krapp, M., Beyer, R. M., Edmundson, S. L., Valdes, P. J. & Manica, A., 2021. A statistics-based reconstruction of high-resolution global terrestrial climate for the last 800,000 years. Sci. Data 8, 228. https://doi.org/10.1038/s41597-021-01009-3
Leonardi, M., Hallett, E. Y., Beyer, R., Krapp, M. & Manica, A., 2023. pastclim 1.2: an R package to easily access and use paleoclimatic reconstructions. Ecography 2023. https://doi.org/10.1111/ecog.06481Marianna Fusco, Behailu Habte, Alice Leplongeon, Clément Ménard, Andrea Manica, Enza E. Spinapolice & Michela Leonardi (2024) The environmental context of the Middle-to-Late Stone Age Transition in eastern Africa: seasonality as a key factor. bioRxiv, ver.2 peer-reviewed and recommended by PCI Archaeology https://doi.org/10.1101/2024.12.09.627606
-
