text: Some 6,000 years ago, vast streteches of the globe where large numbers of humans lived entered a period of increasing aridity. Around the same time, the first great civilizations of the world -- in North Africa, Mesopotamia, the Indus Valley and Northern China -- began to emerge.
  The two developments are not coincidental, argues Nick Brooks, a professor at the Tyndall Center for Climate Change Research and School of Environmental Sciences in the U.K., in a paper published in 2005 that is considerably more fascinating than its title: "Cultural Responses to Aridity in the Middle Holocene and Increased Social Complexity." His thesis is that this great desiccation forced then existing societies to change drastically in order to survive, setting in motion processes of social stratification and urbanization.
  Civilization, in short, is an adapation to climate change. Or, in Brooks' words:
  The archaeologial and paleoenvironmental evidence is consistent with the notion that the development of complex societies in the Middle Holocene was largely the consequence of the responses of the precursor societies to deteriorating environmental conditions associated principally with the orbitally-driven weakening and southward retreat of the northern hempisphere monsoon belt."
  If you're a "Guns, Germs, and Steel" fan, or the kind of geek who gets all hot and bothered when the word "paleo" is prefixed to anything, you will love the cut of Brooks' jib. While previous work investigating the effects of paleoclimatology on ancient civilizations has focused on the disastrous impacts of abrupt changes on existing social structures -- such as the fall of the Akkadian Empire -- Brooks persuasively argues that the complete picture is considerably more complicated. In some cases, desiccation forced widely dispersed, pastoral or hunter-gatherer societies to coalesce in river valleys and develop systems of agriculture and irrigation.
  In his paper, Brooks is careful not to speculate overmuch about what implications his research has into current challenges from climate change. But before we run wild with optimism, imagining how rising temperatures and sea levels and catastrophic weather events will force humanity to take another great step forward, and organize itself more efficiently and sanely in order to adapt to a new environment, we should consider how Brooks interpreted his own research at a conference in September.
  He stressed that for many, if not most people, the development of civilization meant a harder life, less freedom, and more inequality. The transition to urban living meant that most people had to work harder in order to survive, and suffered increased exposure to communicable diseases. Health and nutrition are likely to have deteriorated rather than improved for many.
  "Having been forced into civilized communities as a last resort, people found themselves faced with increased social inequality, greater violence in the form of organised conflict, and at the mercy of self-appointed elites who used religious authority and political ideology to bolster their position. These models of government are still with us today, and we may understand them better by understanding how civilization arose by accident as a result of the last great global climatic upheaval."
  Civilization: a horrible accident forced upon us by climate change. We can only shudder at the prospects of further accidents, waiting to happen.