Based on Part 2 of “A history of world agriculture, from the neolithic age to the current crisis” by Marcel Mazoyer and Laurence Roudart.
Agriculture likely originated with sedentary groups of hunter-fisher-gatherers, in the Neolithic era. They collected seeds or seedlings of wild plants to plant in gardens near their homes, in order to gather them more easily and in greater abundance. They captured groups of wild animals and kept them tied, or in pens.
As soon as a population of plants or animals are cultivated by humans, they are subjected to very different conditions than their counterparts in the wild. In the case of cereals (wheat, maize, rice, millet, sorghum, oats) the plants are harvested by cutting off the top of the plant with a scythe. All the plants are harvested at roughly the same time, and a portion of the harvest is reserved for the following planting season. Late-maturing plants, and plants whose maturation is staggered over several seasons, are disadvantaged because they are harvested before their seeds have a chance to mature and become fertile. Plants with stalks that bend or break easily, and plants whose seeds fall easily to the ground, are less likely to be harvested and re-planted the following season. The characteristic traits of domesticated cereals include non-dormancy, large, difficult-to-remove grains, and strong stalks.
When wild animals are captured and kept by humans, the most timid and sensitive individuals who refuse to eat while in captivity quickly die. The most aggressive and forceful individuals are likely to be quickly killed by the farmer. Larger individuals are slaughtered in preference to smaller ones because they provide more meat, and smaller animals are more able to withstand nutrient deficiencies they experience in captivity. Thus domesticated animals tend to be less sensitive, less forceful, and of smaller size than their wild counterparts.
The selection for certain traits characteristic of domestication was at first unintentional, but later this process became deliberate, with farmers selecting those individuals with the most desirable characteristics for breeding.
Agriculture appeared independently at least four times, in different parts of the world:
– In Syria-Palestine / the Fertile Crescent, 9-10,000 years ago
– In Southern Mexico 4-9,000 years ago
– In Northern China 8,500 years ago
– In Papua New Guinea 10,000 ago
From these centres agriculture spread slowly outwards.