An analysis of palm-sized stone grinders used around 7,000 years ago in North Africa shows that ancient communities resisted new farming practices because of their highly mobile style of life.
Giulio Lucarini and his team from the University of Cambridge were able to spot plant residues, too small to be visible to the naked eye, caught in the pitted surface of several of the stone tools excavated from a cave called Haua Fteah located in northern Libya.
According to earlier studies, the stratigraphy (layers of sediment) at Haua Fteah indicates continuous human habitation from at least 80,000 years ago right up to the present day.
In a paper published recently in the journal Quaternary International, Lucarini and colleagues said the surfaces of the grinders show plant use-wear and contain tiny residues of wild plants that date from the time when, in all likelihood, domesticated grains would have been available to them.
Comparing the characteristic shape and size of the starch found in the grinders' crevices to those in a reference collection of wild and domestic plant varieties collected in different North African and Southern European countries, the researchers were able to determine that the residues, most probably, came from one of the species belonging to the Cenchrinae grasses.
Various species of the genus Cenchrus are still gathered today by several African groups when other resources are scarce. Cenchrus is prickly and its seed is laborious to extract. But it is highly nutritious, especially in times of severe food shortage.
"Haua Fteah is only a kilometre from the Mediterranean and close to well-established coastal routes, giving communities their access to commodities such as domesticated grain, or at least the possibility to cultivate them," Lucarini said.
"Yet it seems that people living in the Jebel Akhdar region may have made a strategic and deliberate choice not to adopt the new farming practices available to them, despite the promise of higher yields but, instead, to integrate them into their existing practices," he added.
Lucarini suggested that North African communities delayed their move to domesticated grains because it suited their highly mobile style of life.
"Opting to exploit wild crops was a successful and a low-risk strategy not to rely too much on a single resource, which might fail. It's an example of the English idiom of not putting all your eggs in one basket," the researcher said.
"Rather than being 'backward' in their thinking, these nomadic people were highly sophisticated in their pragmatism and deep understanding of plants, animals and climatic conditions," he added.
Evidence of the processing of wild plants at Haua Fteah confirms recent theories that the adoption of domesticated species in North Africa was in an addition to, rather than a replacement of, the exploitation of wild resources such as the native grasses that still grow wild in the site.
