adoption of agriculture might have been a rational decision for the adopting groups but have had adverse consequences for society as a whole… there is no mystery in the idea that a technology which is attractive to each group might make all groups worse off…agricultural communities needed to devote substantially more resources to defense than their hunter gatherer predecessors. Sitting and watching the grass grow is not the idyll it seems, for those who are sedentary are also vulnerable. When enemies attack, farmers have much more to lose than hunter-gatherers, who can melt into the forest without losing earthworks, houses, chattels and stores of food. So farmers not only face high risks, but they also need to spend time, energy and resources defending themselves, building walls, manning watchtowers, guarding herds, patrolling fi elds. This means less time and energy, fewer resources, devoted to making food. It could even happen that the greater productivity of the hours they spend growing and raising food is outweighed by the greater time they must spend defending themselves and the food they have grown - meaning that they produce less food in all. Almost certainly the end of the last ice age substantially improved the productivity of agriculture compared with the hostile conditions beforehand. But what would that have mattered if all, or more than all, of the additional benefits of the new farming technology ended up being spent on defense? Such additional defense expenditures could be highly costly even if, in equilibrium, fighting was no more frequent than it had been before the change.What makes the difference, we suggest,is a crucial externality in the technology of defense. Once the very first farming communities began systematically to defend themselves, the fact that they could do so began to make them a threat to their neighbors, including communities who were on the margins of adopting agriculture themselves. For there is no such thing as a purely defensive technology. Even walls around a town can make it easier for attacking parties to travel out to raid nearby communities in the knowledge they have a secure retreat. The club that prehistoric man used to ward off attackers was the same club he used to attack others. Once a community has invested in even a modest army, whether of mercenaries or of its own citizens, the temptation to encourage that army to earn its keep by preying on weaker neighbors can become overwhelming. So, even if the fi rst farming communities were not necessarily any better off than they would have been if no-one had adopted agriculture, once the process had started many communities had an interest in joining in. These interactions could lead each to act ineluctably against the collective interests of all.Agriculture and the associated social changes, notably the adoption of a sedentary way of life, made it possible for societies to accumulate economic resources in a way that hunter-gatherer societies were quite unable to do. If agriculture had been a technology that unambiguously improved the lot of humanity it would hardly be surprising that it had been adopted as soon as it became feasible. That is why the evidence about early Neolithic living standards has been such a puzzle - and perhaps adds substance to the eternal appeal that myths of the noble savage have had throughout human history, since such myths have seemed to suggest, counter-intuitively, that economic development since the time of the alleged fall has been both inevitable and regrettable.At the heart of the story is a fundamental externality from defense activities that make one community more secure make its neighbors less secure.
Actualización: Sobre cómo fue el cultivo de cereales - y la posibilidad de almacenar el excedente - lo que condujo a las jerarquías y al Estado como mecanismo de protección frente al robo http://www.voxeu.org/article/neolithic-roots-economic-institutions