Collagen fingerprinting traces the introduction of caprines to island Eastern Africa.

Courtney Culley,Jillian Swift,Mary E Prendergast,Mark C Horton,Henry T Wright,Jesse Wolfhagen,Ceri Shipton,Samantha Brown,Nicole Boivin,Tabibou A Tabibou,Bourhane Abderemane,Othman Haji,Abdallah K Ali,Alison Crowther,Anneke Janzen

doi:10.1098/rsos.202341

Abstract

The human colonization of eastern Africa's near- and offshore islands was accompanied by the translocation of several domestic, wild and commensal fauna, many of which had long-term impacts on local environments. To better understand the timing and nature of the introduction of domesticated caprines (sheep and goat) to these islands, this study applied collagen peptide fingerprinting (Zooarchaeology by Mass Spectrometry or ZooMS) to archaeological remains from eight Iron Age sites, dating between ca 300 and 1000 CE, in the Zanzibar, Mafia and Comoros archipelagos. Where previous zooarchaeological analyses had identified caprine remains at four of these sites, this study identified goat at seven sites and sheep at three, demonstrating that caprines were more widespread than previously known. The ZooMS results support an introduction of goats to island eastern Africa from at least the seventh century CE, while sheep in our sample arrived one–two centuries later. Goats may have been preferred because, as browsers, they were better adapted to the islands' environments. The results allow for a more accurate understanding of early caprine husbandry in the study region and provide a critical archaeological baseline for examining the potential long-term impacts of translocated fauna on island ecologies.

Highlights

Situated at the nexus of ancient exchange and migration routes that connected mainland Africa with the Indian Ocean world, island eastern Africa is a key region for understanding past human impacts on insular ecologies (e.g. [1,2,3,4,5,6,7])
Reconstructing caprine dispersals in coastal eastern Africa is complicated by the high rate of bone fragmentation in archaeological sites [1,2,33,34] and the close morphological similarity between sheep and goat bones [35,36,37,38]
This paper uses the biomolecular method of collagen fingerprinting to identify caprines to species level at eight archaeological sites across island eastern Africa

Summary

Introduction

Situated at the nexus of ancient exchange and migration routes that connected mainland Africa with the Indian Ocean world, island eastern Africa is a key region for understanding past human impacts on insular ecologies (e.g. [1,2,3,4,5,6,7]). Reconstructing caprine dispersals in coastal eastern Africa is complicated by the high rate of bone fragmentation in archaeological sites [1,2,33,34] and the close morphological similarity between sheep and goat bones [35,36,37,38] These issues often render their bones indistinguishable from one another, and from other similar-sized wild bovids Some islands such as Unguja, Mafia and Kilwa are relatively low-lying, dominated by sparse shrubland thickets that overly thin soils and coral rag Others, such as Pemba and Ndzuani, have more variable topography, higher levels of rainfall and/or natural water sources, deeper soils and more substantial forests. Pemba, which has been separated from the African mainland for approximately 5 million years by a deep marine channel [41], and Comoros, which are oceanic volcanic islands that have never been connected to the mainland, are relatively depauperate in terrestrial mammals compared to Unguja and the near shore islands in the Lamu, Mafia and Kilwa archipelagos [21]

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