Fifteen thousand years ago, when human-hunter gatherers decided to settle down to an agrarian lifestyle, they took the first plunge towards a sedentary existence that has now made hypochondriacs out of the entire human race. The gradual growth of urbanism and the Industrial Revolution marked humankind's final dive towards ulcers and angina.

But why did footloose hunter-gatherers become settled agriculturists? Michael Rosenburg, assistant professor, University of Delaware, holds that when humans changed to settled agriculture, they paid a high cost: shortages of food and fuel due to local resource depletion, plus a downslide in the quality of resources being collected. Ironically, sedentary hunter-gatherers spent more time collecting resources than when they were mobile.

On the other hand, these shortcomings were overcome by storage, increased labour, exploiting high quality resources and technology.

Rosenburg holds that an increase of population among hunter-gatherers leads to food stress and an unfavourable ratio of humans: resources. Increasing competition for resources led to rigid turf marking and land began to be allocated.

Says Roland Fletcher, associate professor, University of Sydney, "Human groups can tolerate only finite amounts of interaction. As population grows, people need more space to mitigate the stress caused by constant interaction. And since communication in those days was limited to speech and one could communicate only over a small range, early agrarian settlements were small in size and expanded according to their communication skills." Says Rosenburg, "Eventually, sedentism is simply cheating at musical chairs and refusing to get up once the music has started."