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

Human-mediated biological exchange has had global social and ecological impacts. In subS-aharan 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

New Evidence on the Development of Millet and Rice Economies in the Niger River Basin: Archaeobotanical Results from Benin

The Niger River is second only to the Nile in length in Africa, and is host to dense populations of agriculturalists that supported in historical times states such as the kingdoms of Songhay and Mali. This is also the region to which the origin of the Niger-Congo language family, including its Bantu offshoot is attributed. Despite this, archaeobotanical evidence for the development of agricultural systems based on both ancient West African crops, like Pennisetum glaucum (L.) R. Br., Vigna unguiculata (L.) Walp. and Oryza glaberrima Steud., and crops introduced to the Niger Basin, such as Sorghum bicolor (L.) Moench. and Gossypium L. sp. has remained limited. In particular the role of multiple crop systems, that included both the wet (rice) and the dry (millets), has not been directly documented archaeobotanically. The present paper presents new archaeobotanical results from 12 sites in Benin that suggest that the rise of larger populations and population centers, like the urban site of Birnin Lafiya, developed only once agriculture diversified beyond pearl millet cultivation to include multiple cereals, as wet rice. The 12 sites are split in four time periods. Flotation results indicate that sites of the first phase (first millennium BC) were dominated by pearl millet, but included sorghum and cowpea. However by the second period (300–900 AD), rice dominated samples, correlated with increasing urbanism, a pattern congruent with existing evidence from Mali. In addition, we report evidence that probable fonio (Digitaria cf. exilis (Kippist) Staph.) also appeared first in this era of diversification, calling into question previous inferences about the antiquity of these West African millets. The third phase, 900–1400 AD, is characterized by an increase of pearl millet and a decrease of African rice. During the last time period, 1400–1950 BC, we notice a disappearance of rice and a diminution of pearl millet and sorghum. Also, the utilizations of tree fruit such as baobab ( Adansonia digitata L.), oil palm (Elaeis guineensis Jacq.), and African olive (Canarium schweinfurthii Engl.) are in constant evolution since the second period. We conclude that agricultural diversification helped to promote urbanization and state formation in the Niger River basin, and that diversification included both use of wetter environments for rice and more marginal dry environments for millet and sorghum