Transition From Wild to Domesticated Pearl Millet (Pennisetum glaucum) Revealed in Ceramic Temper at Three Middle Holocene Sites in Northern Mali

Dorian Q Fuller,Louis Champion,Dominique Commelin,Christian Dupuy,Tim Denham,Michel Raimbault,Aleese Barron

doi:10.1007/s10437-021-09428-8

Abstract

Imprints of domesticated pearl millet (Pennisetum glaucum (L.) R. Br.) spikelets, observed as temper in ceramics dating to the third millennium BC, provide the earliest evidence for the cultivation and domestication process of this crop in northern Mali. Additional sherds from the same region dating to the fifth and fourth millennium BC were examined and found to have pearl millet chaff with wild morphologies. In addition to studying sherds by stereomicroscopy and subjecting surface casts to scanning electron microscopy (SEM), we also deployed X-ray microcomputed tomography (microCT) on eleven sherds. This significantly augmented the total dataset of archaeological pearl millet chaff remains from which to document the use of the wild pearl millet as ceramic temper and the evolution of its morphology over time. Grain sizes were also estimated from spikelets preserved in the ceramics. Altogether, we are now able to chart the evolution of domesticated pearl millet in western Africa using three characteristics: the evolution of nonshattering stalked involucres; the appearance of multiple spikelet involucres, usually paired spikelets; and the increase in grain size. By the fourth millennium BC, average grain breadth had increased by 28%, although spikelet features otherwise resemble the wild type. In the third millennium BC, the average width of seeds is 38% greater than that of wild seeds, while other qualitative features of domestication are indicated by the presence of paired spikelets and the appearance of nondehiscent, stalked involucres. Nonshattering spikelets had probably become fixed by around 2000 BC, while increases in average grain size continued into the second millennium BC. These data now provide a robust sequence for the morphological evolution of domesticated pearl millet, the first indigenous crop domesticated in western Africa.

Highlights

In the fifth millennium BC in northern Mali, represented by AZ22, the overall plant assemblage suggests that Pennisetum dominated other small grasses that were incorporated into some sherds
The AZ22 assemblage provided a point in time and space when the collection of wild Pennisetum was an important part of the food economy, and its processing produced abundant chaff that was utilized as ceramic temper
The research on pearl millet impressions and inclusions in ceramics highlights the great potential of studying ceramic assemblages in regions like Northern Mali for chaff-tempering remains

Summary

Introduction

Cenchrus americanus (L.) Morrone]), is one of the most consumed staple crops of sub-Saharan Africa and tropical India (Brunken et al 1977; Stevens and Fuller 2018). Pearl millet was integrated within the pastoral subsistence system, providing a potent economic package ready for dispersal. The oldest evidence for this situation is documented in the Lower Tilemsi valley (Mali), where pastoralism and pearl millet cultivation were integrated alongside fishing, hunting, and collecting from 2500 BC (Fig. 1; Manning and Fuller 2014; Manning et al 2011). A subsequent rapid spread eastward across the Sahara has been postulated based on evidence for domesticated forms reaching eastern Sudan by approximately 1850 BC (Beldados et al 2018; Winchell et al 2018) and India, via maritime links, by ca. A subsequent rapid spread eastward across the Sahara has been postulated based on evidence for domesticated forms reaching eastern Sudan by approximately 1850 BC (Beldados et al 2018; Winchell et al 2018) and India, via maritime links, by ca. 1700 BC (Boivin and Fuller 2009; Pokharia et al 2014)

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Conclusion