Early urban civilisations, far from being an expression of social and cultural advancement, were simply a means of survival in a changing world.

As the climate became drier 6,000 years ago, and the monsoon system over North Africa and Asia collapsed, people found it increasingly difficult to sustain a hunter-gatherer lifestyle.

Animals they preyed on moved away or died out, while the plants they relied on for fruit and vegetables became harder to find.

Man’s response was to congregate close to rivers and to turn to agriculture as a reliable source of food, giving rise to the first towns and cities, the British Association for the Advancement of Science was told.

The drying of the climate led to a wave of urban civilisations becoming established in Egypt, Mesopotamia, China and Asia, said Nick Brooks, of the Tyndall Centre for Climate Change Research at the University of East Anglia.

“Civilisation did not arise as the result of a benign environment which allows humanity to indulge a preference for living in complex, urban, ‘civilised’ societies,” he said.

“What we tend to think of today as civilisation was in large part an accidental by-product of unplanned adaptation to catastrophic climate change. We see a real shift around 6,000 years ago, where what we see is aridification.

“Until now, the view has been that the world’s first civilisations occurred because the environment was relatively benign. What I argue is the complete opposite: civilisation arose because of a hard environment. This turns on its head the accepted wisdom that civilisation is the product of a benign environment enabling humans to progress.”

Previous research has maintained that from the start of the Holocene period, 10,000 years ago, people were able to benefit from stable climatic conditions and that the creation of urban centres marked an advance in the human condition.

Dr Brooks questioned the assumption that civilisation should be regarded as an advance, claiming that for most people the move into towns and cities meant a harder lifestyle, less personal freedom, a greater chance of wars breaking out and more inequality under autocratic governments.

“People found themselves at the mercy of self-appointed elites who used religious authority and political ideology to bolster their position,” he said. “These models of government are still with us today.”

Dr Brooks said that the drying process was repeated about 3,000 years ago with the rise of the Garamantian society in southern Libya as a reaction to the disappearance of winter rains over Saharan Africa.

“What we see is the disappearance of surface water and the beginnings of agriculture and technology to reach groundwater,” he said.

“As the desert dries out we see people responding to climate change by the creation of the Garamante State.”

Another society, he said, that was likely to have been created as a result of climate change was the Peruvian settlement at Caral.

Just before its creation, about 4,600 years ago, there had been a change in ocean currents, causing colder air at the coast to reduce rainfall. People who had been dependent on fishing moved inland, turning to agriculture. The move to towns meant increasing reliance on agriculture to feed people but rather than crops being seen as a means of creating food surpluses, he said, they were simply seized upon as being predictable.

Once the first cities had been created, it was unlikely that mankind would go back to a hunter-gatherer lifestyle, he told the conference. “It’s a bit like the nuclear bomb — once it’s created, there’s no getting rid of it.

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