Habitat fragmentation and the sporadic spread of pastoralism in the mid-Holocene Sahara

The transition from hunting and gathering to food production in the Central Sahara is complex and variable. The paucity of direct radiocarbon dates and poor preservation of organic remains makes it difficult to track the origins, spread and intensity of food production in this part of the world. Nevertheless, the prevailing narrative in North African prehistory is that cattle pastoralism was the defining characteristic of mid-Holocene African economies, against a backdrop of widespread aridification. Here we present the first ever trans-Saharan analysis of mid Holocene subsistence behaviour using a novel comparative analysis of zooarchaeological remains, organic residue analysis from pottery and palaeohydrological mapping. In some areas, domestic animal resources appear to have played only a marginal role in economic practices, which were typically diverse and potentially even specialised as a response to local environmental conditions. We utilise organic residue analysis (ORA) from 478 potsherds in conjunction with zooarchaeological data to examine animal resource exploitation strategies and environmental change. We demonstrate a significant increase in the d13C value of the C16:0 fatty acid through time, reflecting a substantial increase in C4 vegetation associated with increased aridity. However, despite the changing environmental conditions, North Africa offered a unique context for Neolithic developments. Lakes that persisted during the onset of Saharan aridification provided highly productive and sustainable ecological niches that supported the resilience of hunter-gatherer fisherfolk. Analysis of site distance to water and faunal exploitation strategies reveals a significant correlation between aquatic resource strategies and proximity to water. As such, we propose that rather than being a wave of expansion, as has often been suggested, cattle pastoralism in the Sahara happened as a sporadic expansion, with mid-Holocene populations adapting and specialising in the context of habitat fragmentation and increasing environmental diversity.