State of nature: Radical climate change helped to drive the development of human civilisations and brought the need for political and religious systems that exist around the world today, according to a radical rethink of how humans progressed.
If true, this controversial view implies that civilisation is not our natural state and did not arise as a consequence of human advancement.
Rather, it was the unintended result of our attempts to cope with a drier, less hospitable climate.
There is evidence round the globe that civilisations and urban living emerged between 6,000 and 4,000 years ago because benign humid weather gave way to arid conditions and desertification, said Dr Nick Brooks of the University of East Anglia's school of environmental sciences. He was speaking yesterday at the British Association's annual Festival of Science, which closes this weekend in Norwich.
This view counters current assumptions that cities and agriculture arose during a long period of benign weather that gave humans a chance to develop this complex form of interdependent living. "Civilisation arose not because of a benign environment but a harsh environment," he said.
The first large civilisations emerged about 6,000 years ago in Egypt, Mesopotamia, south Asia, China and northern South America. They all lay in a band ringing the globe that had been humid with plenty of rain and water until a change in the earth's orbit led to a weakening of monsoon systems.
As easy-to-reach surface water supplies dried up and farming became more difficult, people were forced to aggregate in smaller and smaller areas, Dr Brooks argues. It became necessary to defend territory to control resources, requiring armies and civil structures to control them. Religion served to knit these communities together, but social stratification and the development of elite classes also arrived.
As the desert took hold in these areas humans began building dwellings and fortified cities with stone; agriculture became more intensive; deep wells, irrigation systems and other technologies emerged; and wars over resources became common.
This pattern was repeated at all seats of early civilisation in Africa, Asia and the Americas. "What we really see here is people responding to changing climate," Dr Brooks stated.
A compelling argument for his theory is seen deep in the Sahara in what is now the Fezzan region in southwest Libya. Fezzan was the home of the Garamantian culture, a tribal confederation that arose 3,000 years ago and persisted until the collapse of the Roman empire, Dr Brooks explained. It was renowned for its chariots and challenged the power of Rome for the control of north Africa.
The peoples who became the Garamantes inhabited the region at a time when surface water was plentiful. As water sources dried up the population began to compress into what became the Garamantian capital Garama.
The Garamantian culture has come under intensive research in recent decades. The University of Leicester's professor of Roman archaeology, Prof David Mattingly, led a major study of the Garamantes and the archaeological clues that describe the development of their civilisation. It shows the characteristic aspects seen in the emergence in other civilisations, Dr Brooks said.
If this theory holds true then it has profound implications for our understanding of civilisation and its origins, he said.
Left to our own devices and with a benign climate we might have remained in small villages cultivating the surrounding lands, he added.
