The weather suddenly began to get colder and drier, and the hunter-gatherers were faced with a choice: either move on and face the possible wrath of other hungry communities elsewhere or stay put and start farming.
Modern humans began farming centuries earlier than previously thought, a new study claims.
The transition from collecting wild grains to deliberately growing crops was one of the most dramatic changes in human history.
He and his colleagues spent 27 years looking at the remains of a settlement in modern Syria and now believe that the systematic cultivation of cereal crops had already begun around 13,000 years ago, 1-2,000 years earlier than previously thought.
27-year study
Professor Hillman believes the first farmers may have been a small community of hunter-gatherers originally tempted to settle in one place by good food growing wild.
"It was all very rosy for them. It was getting warmer and wetter and they had a food base so luxuriant that they were tempted to settle. But then suddenly things reversed," he told BBC News Online.
The weather suddenly began to get colder and drier, and the hunter-gatherers were faced with a choice: either move on and face the possible wrath of other hungry communities elsewhere or stay put and start farming.
They chose the latter, and as they did so, they changed the way that they harvested.
New technology
Instead of beating wild crops to release their grains, they began to uproot them or cut them down.
This change of approach favoured the survival of different types of crop, and within a short period, one of the things they had domesticated was what we now recognise as rye.
The change was probably not a deliberate policy on the part of the community, but rather a response to the worsening weather.
"We know from modern hunter-gatherers that they are usually reticent to make the change. Recent hunter-gatherers have resented Europeans coming to do just that, foreseeing some of the ecological damage that results," he said.
But in the end, the community prospered, reaching a strength of several thousand.
Flotation recovery
Professor Hillman and colleagues from Oxford University, UK, and Rochester Institute of Technology, US, explain their findings in the journal The Holocene.
They sifted through huge amounts of earth from the dig at Abu Hureyra to recover charred remnants of food.
"The only way this stuff survives is by being exposed to fire. Occasional scraps of food survive and we dunk the excavated earth in water. The little scraps float and we use a machine and a mesh to separate them out," he said.
The evidence from Abu Hureyra is the earliest start to farming so far found by researchers, but the group behind this latest discovery believes it will be backed up by other digs in the area, straddling the Tigris and Euphrates rivers, where the modern way of life began.
"We anticipate that equally early evidence of analogous events will eventually be recovered from other sites in the Fertile Crescent," they write.