Eleven thousand years ago, absolutely no one grew their own food. Instead they lived off of wild game, fish, and plants. Today only a tiny handful of people continue to live this way. Instead we live off of food that we cultivate deliberately or that someone else cultivates for us. Indeed, by the time everyone in this room is dead, there will probably be no primarily hunting and gathering cultures left. Their members will have dispersed and been assimilated by agricultural cultures.

Why did this change occur? After all, humans had done nicely as hunter/gatherers for many millenia. When you think about it in depth, this is really a restatement of Yali's question.

Traditionally, members of agricultural cultures would have answered that it was because of the inherent superiority of their life style, citing:

Diamond provides an alternate view based on the synthesis of anthropological, archeological, and historical data that suggests something more complex has happened.

Origins of Agriculture: Advantages of the hunter-gatherer life:

Advantages of food production:

Agriculture, thus, not only has immediate benefits, cultures that adopt it soon find that they can't back away from it without rising against their ruling class and condemning much of their newly increased population to starvation. In short, they have been thrust from the Garden of Eden and are stuck with a back-breaking life style that will leave them stunted and feeble as individuals but highly competative as societies.

Cradles of Agriculture

Diamond points out some paradoxes about the geography of the definite centers of origin:
The contrast is especially striking in the southwest US where, in harsh Arizona and the Colorado Plateau, agriculture was practiced for centuries next to the abundant environment of southern California (right), whose people remained hunter-gatherers.

Suggests that:

Plants to domesticate

Conscious, overt criteria for plant domestication:

Unconscious criteria for plant domestication:

The Geography of domestication

Suitable plants aren't uniformly distributed. Indeed, although traditional agriculturalists have added many plants to our basic package, great efforts over the last two centuries have added very little that ancient people didn't already know about. Thus, we have a good inventory of domesticatable plants, so we can confidently say that:

Domestication of large mammals

Again, certain traits predispose some animals to domestication and exclude others:

Failure to meet any of these criteria eliminates a large mammal from consideration. (But note pets, and domestic hunters like cats and ferrets.)

The winners:

Once animal is under domestication, its traits can be modified by artificial selection. - Paedomorphic traits favored to promote tractability. Consider the half-century old effort in Russia to develop pet silver foxes. Tractable foxes have reduced production of adrenaline. Selecting for this requires selecting higher up on a biochemical cascade that also produce a cascading phenotypic effect that seems strangely familiar.
But domestic animals come with a down-side. Living in close association with them has provided a splendid evolutionary opportunity to their pathogens to colonize a new host: humans.

Pathogenic organisms that have made the jump to humans include:

  • Origins in domestic animals

    Each of these are examples of crowd diseases - diseases in which the pathogen takes advantage of host behavior and proximity for transmission. Of course, settled communities with high populations provide a selective pressure for such transmission that thinly-spread hunter-gatherer societies didn't.

    When farmers and hunter-gatherers meet:

    Such interactions aren't necessarily hostile. Indeed, cooperative arrangements based on division of labor can include:

    So why do the non-agriculturalists always seem to disappear? When agriculturalists interact with their neighbors, they have certain advantages, regardless of their intentions:

    Agriculturalists, who already had a population density advantage, will find themselves facing fewer and fewer hunter-gatherers because crowd diseases will kill more of them proportionally. E.G: English colonists in New England, including the "Pilgrims" had an easier time of it than they might, because they arrived after crowd disease plagues had decimated aboriginal populations. The town of Plymouth was built among the ruins of an evacuated Native American town.

    All of this is despite the fact that, left on their own, hunter gatherers would typically be larger and healthier than farmers. Only two factors have altered this in recent times:

    A classic case study - the Bantu expansion