Archaeological evidence for persistent occupation of marginal environments in southeastern Ethiopia during the Early Holocene

Abstract

The sparseness of securely dated archaeological sequences sampling the earliest Holocene in the Horn of Africa obfuscates human adaptive responses to the period's predominantly wet conditions and intermittent arid episodes. New radiocarbon dates and archaeological material from Dibé rockshelter show that the poorly drained, semi-arid southeastern Ethiopian lowlands were persistently occupied from 11.2 to at least 10.2 cal ka BP. The absence of a hiatus or abrupt sedimentary changes suggests generally stable environmental conditions during the period represented. Artefact accumulation rate increased, and retouched tools and volumetric cores appeared in the sequence after 10.4 cal ka BP. Locally available cryptocrystalline silicates dominate the excavated as well as surface assemblages while exotic raw material and pigment use is limited to a single excavated layer, suggesting nuanced mobility and/or exchange networks after 10.4 cal ka BP. We infer that peak hydroclimatic conditions during the period facilitated human habitation of marginal environments, with flexible adaptive responses enabling persistent occupation away from the more stable and ecotonal hotspots in the broader region. The sensitivity of such environments to subsequent pronounced hydroclimate changes likely led to the site's abandonment ∼9.8 ka BP, as estimated based on an age-depth model. Our results reinforce previous inferences about the geographical and temporal variability of Holocene climate fluctuations and attendant adaptive responses.