Coastal caprines: using ZooMS to trace the spread of domesticates in coastal eastern Africa

Abstract

Domestic caprines (sheep, Ovis aries and goat, Capra hircus) were among the most important livestock introduced to Africa by past humans and have remained a valuable part of present-day subsistence and economic systems. Eastern Africa’s Swahili coast is a key region for studying sheep and goat dispersals owing to its role as a major nexus for regional and long-distance trade, exchange, and migration. Emerging archaeological datasets are revealing regional variation in the timing and tempo of the spread of domesticates in sub-Saharan Africa, and the degree to which they were incorporated into economies alongside hunting and foraging. Despite these advances, however, poor bone preservation and morphological overlap between domesticates and wild taxa have been a major hinderance to the development of more sophisticated models for farming transitions in this region.To address these issues, this project employed Zooarchaeology by Mass Spectrometry (ZooMS) to identify archaeological sheep and goat remains at Swahili sites dating to the Early and Middle Iron Ages (c. 300–1000 CE). The main aim was to provide a more robust empirical baseline for caprine presence in order to examine their relative importance in early food economies, as well as the role of domesticates in forager-farmer interactions and island colonisation. A sample of 511 archaeological specimens were analysed from 11 sites across the coastal hinterland and offshore islands, representing the largest ZooMS-based study in Africa to date, in both size and scale. It thereby provides an unparalleled opportunity to assess the timing and importance of caprine introductions to a wide range of archaeological and cultural settings including hunter-gatherer-occupied rockshelters, food-producer villages, and pre-urban trading ports.This thesis is divided into three research papers. The first (Chapter 3) examines the role of introduced domesticates in hunter-forager economies at Panga ya Saidi in southeastern Kenya. Using ZooMS, all three major livestock species (sheep, goat and cattle, Bos taurus) were identified at the site for the first time, albeit in low numbers relative to wild bovids. These findings contribute to broader interpretations of the interaction between foragers and agro-pastoralists during the Iron Age, and the role livestock played in facilitating these relationships. It also supports other archaeological and archaeogenetic datasets showing the long-term persistence of hunter-forager peoples and lifeways during this transition.The second paper (Chapter 4) focuses on the introduction of caprines to the Swahili islands. ZooMS analysis of faunal remains from eight sites in the Zanzibar, Mafia and Comoros archipelagos demonstrated that sheep and goat were present at a wider range of sites and at much higher frequencies than previously detected, suggesting their economic importance relative to hunting had been underestimated. The dominance of goat relative to sheep and cattle suggests that early farmers preferred browsing livestock, which were better suited to island environments. This study has also provided a more robust archaeological baseline for future research on the potential ecological impacts of human-mediated faunal translocations to eastern Africa’s islands.The third paper (Chapter 5) brings together the full ZooMS dataset to compare morphological and biomolecular approaches to faunal identification and assess the applicability of ZooMS at tropical latitudes. Findings indicate that ZooMS significantly increased species-specific identifications overall, and that specimens that are morphologically more identifiable in terms of both element and taxonomic category have better collagen preservation and are thus better ZooMS candidates compared to non-morphologically identifiable specimens. This study provides a methodological basis for future application of ZooMS in this region and demonstrates the importance of applying biomolecular and morphological approaches in tandem. Together, these studies have not only expanded our empirical baseline of secure caprine identifications at early Swahili sites but have contributed to our understanding of how sheep and goat, two behaviourally distinct domesticates, were integrated into coastal Iron Age economies and the sociocultural choices involved in this process. This research has also demonstrated the huge potential for ZooMS in coastal eastern Africa, showing that high success rates of collagen extraction are possible from archaeological material dating to within the last ~2000 years, despite the harsh tropical environment. The methodological advances presented in this thesis are crucial for future archaeological work, and with the implementation of ZooMS into more African contexts alongside direct dating of securely identified remains, can overcome challenges that have encumbered farming dispersal debates.