What do the archaeologists have to say - where did farming start?

For the Ruddiman hypothesis to work, it is necessary to show that there was sufficient anthropogenic activity starting around 8,000 BP to initiate the kind of environmental changes suggested. Evidence is needed to show that agricultural behaviour had spread over a wide enough area of the planet, early enough for it to manifest the suggested impacts on the atmospheric concentrations of CO2 and CH4. We need to look to archaeological evidence to understand where agriculture originated, what form it took and how far it had spread by when. Then we need to use that evidence to calculate how much of a contribution agriculture made to CO2 and CH4 concentrations.

To model the spread of agriculture we need to establish a time and place for the point of origin and then estimate the rate of diffusion. The problem is that there is significant debate and disagreement between researchers over when and where farming started and how far and fast it spread. What are the alternatives?

The classic "fertile crescent" origin proposed that farming emerged between 12,000 and 8,000 years BP, after the Younger Dryas cool period, in the valleys of the Taurus mountains of southern Anatolia and of the Levant. While that is the likely earliest origin, archaeological evidence now supports the theory that farming originated at possibly more than twenty locations across most continents over time and involved a number of species of animal and plant.


From: Current perspectives and the future of domestication studies (Larson et al, 2014)

All these animals and plants originated in wild species. Zooarchaeologists and palaeobotanists have developed ways of detecting whether a plant or animal has been domesticated, that is the species has been intentionally modified by human selective actions to change it genetically, morphologically or behaviourally. For example, archaeological wheat seeds, often found in dumps and pits created by Neolithic peoples, are examined microscopically to see if they are shattering or non-shattering; the non-shattering form is indicative of domestication as it is the form which is harvested most efficiently with scythes.

The rate of change during domestication is another area of research which has shown that plant domestication can be an extended process taking thousands of years. The early rice project not only seeks out the origins and nature of rice domestications but also links the effects of rice with increased atmospheric CH4. We are now starting to understand and quantify the environmental effects of irrigation, terracing, slash-and-burn forest clearance and other anthropogenic behaviours that come with farming.

There are many reasons why people may have started to farm. The warm period after the Younger Dryas favoured plants. The human population was increasing and with it came increased competition for land and resources. Humans were developing a shared knowledgebase of experience which was passed between generations and enriched through cultural transmission. Once the commitment to farming had been made by investing energy in modifying landscapes, was it too hard to revert to the hunting and gathering strategies for food procurement that humans had used for 200,000 years? A comfortable niche had been constructed, how far and fast did it spread out across the planet?