Pearl millet (Pennisetum glaucum) is today an enormously important staple cereal of both sub-saharan Africa and parts of India; and an important forage crop in the Americas. Archaeological evidence suggests that pearl millet was first domesticated in the grasslands and park lands at the edge of the savanna-sahel desert of west Africa ca 2500 BC, and spread rapidly out from there. Researchers believe that the development and spread of millet farming was spurred by the increasing desiccation of the Sahara Desert after 3000 BC.

Millet domestication followed the domestication of cattle in Africa by at least 1500 years, and it is hypothesized that that is because mobile pastoralism was better suited to the region prior to the onset of the dessication.

By the second millennium BC, pearl millet was the primary food plant in Mali, Mauritania, Ghana, Burkina Faso and Cameroon. Pearl millet appears in south Asia no later than 2300 BC, with early evidence at Gujarat, Koethe, Babor Kot, and Surkotada in India.

Evidence for the domesticated variety of pearl millet is first indicated by a non-shattering rachis. A rachis is the stem on which the millet grains cling, and in wild forms of millet, the rachis shatters when the seed is ripe, allowing it to disperse naturally. Domesticated forms have a non-shattering rachis, meaning that the cultivator can reap pearl millet when it is ripe and expect to keep most of the seeds. In addition, over time domestic pearl millet grains have been documented to increase in size.

Earliest Evidence

The earliest evidence for pearl millet domestication comes from the Lower Tilemsi Valley in eastern Mali, specifically at the sites of Karkarichinkat Sud and Karkarichinkat Nord.

Dates for dependence on the grain (not necessarily domesticated) at these sites begin ca 5500-4500 BP (or ~3500-2500 BC). Stable isotope analysis of human remains from these sites also support reliance on millet at this date. Enzyme similarity of modern pearl millet supports this as well, pointing to western Africa, with a domestication center between northeast Mali to Lake Chad.

Birimi in northern Ghana contained domesticated millet grains direct-dated to 3490 BP (1787-1744 cal BC). Ceramics at Dhar Tichitt in southwestern Maritania contained impressions of domesticated pearl millet dated to 3800 BP.

In addition to the presence of millet seeds, rachises, and bristle fragments within the assemblages at the Karakarichinkat sites, archaeological evidence for the presence of domesticated pearl millet includes pottery tempered with millet chaff.

Dates supporting the domestication of pearl millet at Karkarichinkat included Accelerator Mass Spectrometery (AMS) radiocarbon dates on associated charcoal including one firmly identified grain of domesticated pearl millet, as well as optically stimulated luminescence (OSL) dates on potsherds and soil sediments. Together, these put the domestication of pearl millet at approximately 2500 BC.

Sources

This glossary entry is a part of the About.com guide to Plant Domestication, and the Dictionary of Archaeology.

Finucane B, Manning K, and Touré M. 2008. Late Stone Age subsistence in the Tilemsi Valley, Mali: Stable isotope analysis of human and animal remains from the site of Karkarichinkat Nord (KN05) and Karkarichinkat Sud (KS05).Journal of Anthropological Archaeology 27(1):82-92.

Giblin J, and Fuller D. 2011. First and second millennium A.D. agriculture in Rwanda: archaeobotanical finds and radiocarbon dates from seven sites.Vegetation History and Archaeobotany 20(4):253-265.

Manning K, Pelling R, Higham T, Schwenniger J-L, and Fuller DQ. 2011. 4500-Year old domesticated pearl millet (Pennisetum glaucum) from the Tilemsi Valley, Mali: new insights into an alternative cereal domestication pathway.Journal of Archaeological Science 38(2):312-322.

Nixon S, Murray M, and Fuller D. 2011. Plant use at an early Islamic merchant town in the West African Sahel: the archaeobotany of Essouk-Tadmakka (Mali).Vegetation History and Archaeobotany 20(3):223-239.

Pearsall DM. 2008. Plant domestication. In: Pearsall DM, editor. Encyclopedia of Archaeology. London: Elsevier Inc. p 1822-1842.