Kharaneh IV (Jordanie):Our ancestors chose reeds over grain when quitting nomadic life
Bob Holmes
The grass is always greener… than the grain? Mark Daffey/Lonely Planet Images/Getty
When ancient hunter-gatherers first began to give up their nomadic life, they weren’t just chasing the grain. Rather than looking for big payoffs from harvesting cereal grains, it seems at least some groups may have been playing it safe.
If so, the transition to sedentary life — the first big step toward agriculture — may have been more complex, and more varied, than archaeologists thought.
The standard view has been that around 20,000 years ago, our ancestors began to stay in one place for long periods so that they could exploit the wild grains growing there, which provided a dense source of energy. After many generations of selection, these grains became the modern domesticated cereals on which most of our civilisations depend.
Archaeologists have had few opportunities to test this view because plant remains from the early stages of this transition are scarce. Recently, however, researchers have begun to use phytoliths — microscopic silica crystals that form in plant tissues and persist for millennia — to investigate which plants would have been around at early archaeological sites.
Cereal monogamy
Monica Ramsey, an environmental archaeologist at the University of Toronto, Canada, and her colleagues studied phytoliths at the 22,000-year-old Kharaneh IV site in Jordan, one of the first places to show evidence of long-term residence.
To their surprise, they found few phytoliths from cereal grains. Instead, the vast majority of phytoliths came from wetland plants such as rushes and sedges. These plants yield many fewer calories than grains do, but they are available year-round, and in dry years as well as wet ones.
Most likely, Ramsey suggests, the inhabitants of Kharaneh began spending longer periods near the wetlands to take advantage of this dependable resource. That dependability, in turn, may have let them experiment with harvesting grains in the surrounding steppes during good years.
In other words, the inhabitants of Kharaneh were taking advantage of what the local environment gave them. “At Kharaneh, they’re sitting on the edge of this nice big marsh wetland,” says Ramsey. “In other areas, they might not have had those resources available, so their lifestyle might have been very different.”
The result would have been a complex pattern of reasons for settling into sedentary life, in contrast to the simple, grain-centred explanation usually given.
Other archaeologists say Ramsey’s ideas make sense. “It is clear that these are not wild cereal-focused foragers, which some have assumed must have characterised the pre-agricultural stages,” says Dorian Fuller, an archaeologist at University College London.
However, he notes that cereal-focused groups may have also existed in nearby environments.
Journal reference: PLoS One, DOI: 10.1371/ journal.pone.0164081