Reconstructing Asian faunal introductions to eastern Africa from multi-proxy biomolecular and archaeological datasets

Abstract

Human-mediated biological exchange has had global social and ecological impacts. In sub-Saharan Africa, several domestic and commensal animals were introduced from Asia in the pre-modern period; however, the timing and nature of these introductions remain contentious. One model supports introduction to the eastern African coast after the mid-first millennium CE, while another posits introduction dating back to 3000 BCE. These distinct scenarios have implications for understanding the emergence of long-distance maritime connectivity, and the ecological and economic impacts of introduced species. Resolution of this longstanding debate requires new efforts, given the lack of well-dated fauna from high-precision excavations, and ambiguous osteomorphological identifications. We analysed faunal remains from 22 eastern African sites spanning a wide geographic and chronological range, and applied biomolecular techniques to confirm identifications of two Asian taxa: domestic chicken (Gallus gallus) and black rat (Rattus rattus). Our approach included ancient DNA (aDNA) analysis aided by BLAST-based bioinformatics, Zooarchaeology by Mass Spectrometry (ZooMS) collagen fingerprinting, and direct AMS (accelerator mass spectrometry) radiocarbon dating. Our results support a late, mid-first millennium CE introduction of these species. We discuss the implications of our findings for models of biological exchange, and emphasize the applicability of our approach to tropical areas with poor bone preservation.

Dental Shape Variation and Phylogenetic Signal in the Rattini Tribe Species of Mainland Southeast Asia

“…Identification of rodents to species levels informs research about the species composition of local rodent communities and how these have changed through time, particularly in the case of changes due to human activity (Weissbrod et al 2017), but also in environmental changes (Cuenca-Bescós et al 2009;Stoetzel et al 2011). Identification to species level is also central to the understanding of the rate and route of species translocations and invasions (Prendergast et al 2017). However, this is often hindered by poor DNA preservation conditions of hot and humid environments, particularly in regions such as Southeast Asia.…”

What Makes a Dog? Stable Isotope Analysis and Human-canid Relationships at Arroyo Hondo Pueblo

“…"Taxon (ZA)" indicates our identification, which was based on morphological characteristics alone. *After Kemp et al (2017).…”

Commensal Rats and Humans: Integrating Rodent Phylogeography and Zooarchaeology to Highlight Connections between Human Societies

“…[ 38,46 ] Recent development of low‐cost, minimally destructive collagen fingerprinting (“ZooMS”; Figure 2 ) mitigates this problem, allowing distinction between R. rattus, R. norvegicus , and R. exulans , at least. [ 17,47 ] Confident dating can be problematic due to bioturbation and to the burrowing behaviors of rats, potentially allowing recent remains to penetrate earlier deposits. Direct radiocarbon dating is thus invaluable, and is now possible on very small samples, [ 48 ] although its utility is limited by the shape of the calibration curve—notably for the eighteenth to early twentieth centuries ( Figure 3 )—and by carbon reservoir effects where rats consumed food from aquatic ecosystems.…”

“…[ 15,16 ] The earliest sub‐Saharan African zooarchaeological finds, from seventh to eighth century AD Zanzibar and Pemba islands, coincide with the emergence of long‐range trade networks around the Indian Ocean. [ 17 ] This may have led to the high frequency mitochondrial haplotypes found along the eastern African coast and Madagascar, which contrast with west African haplotypes more closely associated with the Arabian peninsula. [ 13,18 ]…”

“…[ 37 ] The dispersal of black rat from India to the Mediterranean and Africa, meanwhile, probably owes more to trade networks than to human population movements. [ 17,38 ] Combining these geographically separate events for expansion of commensals builds an underlying picture of which human societies were connecting with each other and when; and different species identify unique connections based on their natal ranges.…”