The Neolithic Agricultural Revolution

Note: the following is based on two chapters from Jared Diamond's Guns, Germs, and Steel entitled "How To Make Almond", and "Apples or Indians".

The concept should be familiar to you by now: surplus foods enabled large, concentrated, sedentary populations, specialization of labor, and social stratification—civilization. Of course, not all of the peoples on Earth followed this path and among those who did, starting dates vary widely from many millennia b.c.e. to relatively recently in the contemporary era.

Historically, the range of dates for domestication is large. The reason why many of the world's cultures underwent similar changes at vastly different times is a function of evolution and geograpghy. Cereals and grains, for example, along with peas, are the oldest cultivated crops, dating to 8,000 years ago, possibly even earlier. Olive cultivation dates to 4,000 years ago, but the strawberry not until the Middle Ages, and pecans not until 1846. Why this is so is a function of a plant suitability for cultivation. It is also a function of natural selection (evolution) and closely tied until recently to regional variations in climate.

Jared Diamond poses the question as follows: How did certain ancestor plants get turned into crops? Further complicating this question is the fact that the wild ancestors of crop foods (such as those in the titles of the two chapters mentioned above, almonds and apples) are bitter, acrid, and/or poisonous to the point of lethality. In fact, some of the food crops commonly consumed, such as yucca, are poisonous until thoroughly cooked.

In order to answer the question of what brought about the first, or neolithic, Agricultural Revolution, Diamond suggests that it is helpful to consider the perspective of plants, which unlike most animals, cannot move to procreate and spead.

Angiosperms

Just like every other living organism, agriculturally useful plants evolved ways that enhanced the chance that their offspring survive. Since they are sedentary, plants have also evolved complicated physical and chemical characteristics designed to either entice or to prevent predation by animals.

First, consider how plants hitchhike on (or inside) animals. A walk through a field will likely result in an accumulation of seeds and pollens on your shoes, clothes, or skin.

To procreate and spread, animals can move around – plants must 'hitchhike:

  • some seeds have evolved to float on air and water, while others rely on animals
  • the principal way that plants have done this is to wrap their seeds in tasty flesh and advertise in the form of appealing colors and/or scents
  • birds, mostly, but other animals too, are attracted to the fruit, either eat it, or carry it away to be eaten
  • seeds would be either spit-out or defected
  • wide dispersal more so guarantees survival
  • the more varied environments, the more likely a variant will survive
  • plant seeds have evolved to resist digestion – in fact, some fruits be eaten and defected
    • example: there is an African melon that must be eaten by an aardwolf to propagate—its skin is too hard rot (like a gourd) and its seeds would not otherwise be able to germinate

The process of animal selection is well-illustrated by the strawberry:

  • a wild strawberry will have immature seeds when green and sour, but viable seeds when ripe – red, sweet, and appealingly scented
  • birds are attracted to the red and sweet and carry away the fruit
  • birds who try to eat the green will favor the red for obvious reasons
  • strawberry variants whose seeds mature while the fruit is green and sour will be less likely to be carried off by birds
  • therefore the green fruit with immature seeds will not be consumed and will not be "selected"
  • the red fruit/mature seed variant is selected

But strawberries are only one of the many fruit/berries first selected by animals that humans would later use:

  • berries – birds
  • mangos – bats
  • acorns – squirrels
  • and so on

Humans

Humans collected from the natural variants developed by the interaction—a form of "generic engineering"—of plants and animals

  • humans would eat, defecate, drop, or spill some of what was collected
  • humans would discard what was collected and not eaten in trash heaps (fruits/berries that rotted)
    • naturally, humans would collect only the most prized – biggest, sweetest, fleshiest specimens: that's how berries get big
  • humans would notice that the paths they frequented (because of dropped fruits) and trash heaps would produce these selected fruits
  • humans then purposely planted them in other places

But fruits are not really where the agricultural revolution took off; it took off with grains and pulses. Why? Animals require fodder (or feed), and to domesticate animals means to corral them and to provide them with food.

Meat and milk products could then become important foodstuffs.

  • domestication of animals for meat and milk also requires to some degree either a plant "crop" or the management of available pasture

Surprisingly, to understand the process of domestication, consider the point of view of the plant!