Cereal crops domesticated 500 years earlier than thought

Cereal crops such as wheat and barley were first domesticated in the Near East some 10,500 years ago, then spread west, to Europe and the Mediterranean, and east, through central and south Asia.

The earliest evidence of cereal crop domestication in North Africa comes from the Fayum area of middle Egypt, and dates back to around 4350 BC. Further south, in northern and central Sudan, however, plant remains are scarce, and so archaeologists assumed that Neolithic communities in this region subsisted by raising livestock.       

In one of the few studies of its kind¹, archaeobotanist Marco Madella of Pompeu Fabra of the University in Barcelona and his colleagues examined microscopic plant remains from the region, to give a clearer picture of how agriculture spread south into North Africa.

Working at two Neolithic cemeteries in northern and central Sudan, the researchers examined phytoliths obtained from samples of dental plaque from 20 of the skeletons. Sometimes referred to as ‘plant stones,’ phytoliths are formed when silica in ground water is taken up by plants and deposited between the cells, giving rise to tiny, skeleton-like structures.

The phytoliths were compared to a reference collection to confirm that they were indeed cereal crops. Radiocarbon dating further revealed that the phytoliths predated those previously found in the Neolithic Fayum – those from the cemetery in northern Sudan were at least 7,000 years old, and that those from central Sudan were between 7,500 and 6,500 years old.

The wild ancestors of these crops are not present in the region, so the phytoliths probably originated from domesticated plants that were brought down from the Nile valley. The findings further suggest that these populations had a diet that included a wide variety of different grains. “These communities had a broad-spectrum exploitation of plant resources, with various millets and legumes, and including domestic cereals cultivated locally,” says Madella. 

Allison Weisskopf, a phytolith analysis expert at University College London, says that although the findings are interesting and innovative, the work it is not conclusive. “One sample produced only 32 phytoliths, and cannot demonstrate domestication,” she says, “but the other is much larger, and demonstrates exploitation of a broad spectrum of wild grasses.”

“While the argument for domesticated cereals needs more evidence, the phytoliths demonstrate how useful a well-identified micro fossil data set can be for understanding plant exploitation.” 

Madella and his colleagues are now expanding their search to other Neolithic cemeteries of the area, with “a more systematic collection of samples from the graves, grinding stones deposited as grave goods, and dental calculus,” he says. 

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