THE period when humans stopped hunting and gathering and settled down to become farmers is one of the most important in history. It ranks with the original human exodus from Africa about 60,000 years ago, which led to Homo sapiens becoming a global species, and the beginning of the industrial revolution, 250 years ago, when many people stopped being farmers and began to earn their livings in other ways. Yet it is not well understood. A piece of research published this week in the Proceedings of the National Academy of Sciences by Ian Kuijt of the University of Notre Dame, in Indiana, and Bill Finlayson of the Council for British Research in the Levant, may shed more light on the matter.

Dr Kuijt and Dr Finlayson have been excavating a site called Dhra, in Jordan, near the Dead Sea. They have uncovered evidence that sophisticated ways of storing grain had been developed well before cereals were actually domesticated. The discoveries the two researchers describe appear to be small granaries, about three metres across and three high. They are made of mud, in some cases reinforced by stone. But, being over 11,000 years old, they predate the domestication of cereals in the Middle East by a millennium. Instead, they seem to have been used to store wild barley and wild oats.

The period leading up to the domestication of cereals was one of erratic climate change, as the last ice age ended. In the Middle East people started to build settlements as early as 15,000 years ago, a period called the Early Natufian, but a drying of the climate made them nomadic again between 12,800 and 11,500 years ago. A second attempt to settle, known to archaeologists as the Pre-Pottery Neolithic A, then began and led, arguably, to modernity—at least in the West.

The granaries themselves are circular and quite sophisticated. From the arrangement of a system of internal stone supports, for example, they appear to have had raised floors. That would have allowed air to circulate, reducing the risk of fungal spoilage and providing some protection against rodents. The floors also sloped, apparently deliberately—probably to make moving grain around them easier. And evidence of barley straw at the site helps confirm that the buildings were, indeed, used to store grain.

To settle down in one place requires a reliable food supply, so the discovery of granaries is no surprise. Pits that might (or might not) have held grain have already been found, but the latest discovery is on a far grander scale. It helps confirm what had previously been suspected—that it was a technological change to the gathering half of the hunting-and-gathering lifestyle that propelled the domestication and cultivation of crops.

What happened next (indeed, what was probably already happening) was the deliberate planting of wild seeds, in order to make the gathering process less onerous. From there, it was but a short leap to choosing seeds from the most productive plants to sow next season and the consequent evolution, partly by accident and partly by design, of early versions of many of the grains that now feed the world.