Why agriculture?

DelanceyPlace.com has a selection from This Fleeting World by David Christian:

Agriculture arose independently in multiple, unconnected areas of the world in roughly the same historic timeframe. One of the great mysteries of history is why it arose at all. Scientists believe that foragers (or hunter-gatherers) lived comparatively leisurely lives with good nutrition, working just a few hours each day, while those in agricultural communities toiled almost ceaselessly and had comparatively poor nutrition:
At present we lack a fully satisfactory explanation for the origins of agriculture. Any explanation must account for the curious fact that, after two hundred thousand years or more, during which all humans lived as foragers, agricultural lifestyles appeared within just a few thousand years in parts of the world that had no significant contact with each other. The realization that agriculture arose quite independently in different parts of the world has undermined the once-fashionable view that agriculture was a brilliant invention that diffused from a single center as soon as people understood its benefits. That view was also undermined after researchers realized that foragers who know about agriculture have often preferred to remain foragers. Perhaps foragers resisted change because the health and nutritional levels of the first farmers were often lower than those of neighboring foragers, whereas their stress levels were often higher. If agriculture depressed living standards, then an explanation of the origins of agriculture must rely more on 'push' than on 'pull' factors. Rather than taking up agriculture willingly, we must assume that many early agriculturalists were forced to take it up.
The first agricultural villages appeared after many centuries during which foragers intensified their exploitation of particular favored resources, adapting their tools and techniques with increasing precision and efficiency to local environments. This was the first step toward agriculture. The end of the last Ice Age was a crucial enabling feature, making agriculture possible for the first time in perhaps a hundred thousand years.
The end of the last Ice Age also coincided with the final stages of the great global migrations of the era of foragers. As the anthropologist Mark Cohen has pointed out, by the end of the last ice age few parts of the world were unoccupied, and by the standards of foragers some parts of the world may have seemed overpopulated. Perhaps the coincidence of warmer, wetter, and more productive climates with increasing population pressure in some regions explains why, in several parts of the world, beginning ten thousand to eleven thousand years ago, some communities of foragers began to settle down.
Eventually some sedentary or semi-sedentary foragers became agriculturalists. The best explanation for this second stage in the emergence of agriculture may be demographic. As mentioned earlier, modern studies of nomadic foragers suggest that they can systematically limit population growth through prolonged breast feeding (which inhibits ovulation) and other practices, including infanticide and senilicide (killing of the very young and the very old, respectively). However, in sedentary communities in regions of ecological abundance, such restraints were no longer necessary, and may have been relaxed. If so, then within just two or three generations, sedentary foraging communities that had lived in regions of abundance for a generation or two may have found that quite quickly they began to outgrow the resources available in their environment.
Overpopulation would have posed a clear choice: migrate or intensify (produce more food from the same area). Where land was scarce and neighboring communities were also feeling the pinch, there may have been no choice at all. Sedentary foragers had to intensify. However, even those foragers able to return to their traditional, nomads may have found that, in just a few generations, they had lost access to the lands used by their foraging ancestors, and had also lost their traditional skills as nomadic foragers. Those communities that chose to intensify had to apply already-existing skills to the task of increasing productivity. They already had much of the knowledge they needed. They knew how to weed, how to water plants, and how to tame prey species of animals. The stimulus to apply such knowledge more precisely and more systematically was provided by overpopulation. Global warming at the end of the last Ice Age was what made intensification possible by increasing the range and productivity of many edible crops such as wheat and wild rice.
These arguments appear to explain the curious near-simultaneity of the transition to agriculture at the end of the last Ice Age. After agriculture had appeared in any one region, it spread, primarily because the populations of farming communities grew so fast that they had to find new land to farm. Although agriculture may have seemed an unattractive option to many foragers, farming communities usually had more resources and more people than foraging communities. When conflict occurred, more resources and more people usually meant that farming communities also had more power.

Rico says agriculture was, and is, a good thing...