Origins of Agriculture

Some 10,000 years ago, people started to switch from gathering wild resources to planting crops and raising animals. Although it is best studied in the Near East, agriculture most likely began independently in a number of regions, including China and Central America.

World map with earliest known occurrences of crops, starting around 8000 BC
The origins of crop plants across the world. Created after Balter, 2007, on this map, and updated. CC Attribution

Today, farming seems like a clear step forward from hunter-gatherer lifestyles. The first farmers, however, seem to have been less healthy than their foraging ancestors, and may have had to do more work. A number of explanations have been advanced for the shift, but the key advantage was probably the ability to produce more food from an area of land. Agriculture is also tied up with the shift from nomadic wandering to settled life, although neither is clearly cause or effect.

Rice panicle
Green bean seedlings. Image by OakleyOriginals (flickr) [CC BY]

A wide array of crop plants were exploited, but there are certain patterns. Two plant families in particular have been domesticated many times: the grasses (rice, maize, wheat, broomcorn millet, finger millet, teff, etc.) and legumes (soybean, peas, lentils, chickpeas, old and new world beans, peanuts, etc.).

This project aims to work out how certain species were selected for cultivation. Plant remains from prehistoric hunter gatherer sites (such as Ohalo II) show that our ancestors used a diverse array of plants, including many which were not later farmed. What was special about those which became our crops? I hope to draw together information from existing databases to study this.

Another key stage is domestication, through which wild plants became crop species, with changes such as larger seeds, and keeping the seeds on the plant until they're harvested. Can we explain these changes as evolutionary responses to the new conditions of planting and harvesting, or could some changes only have been due to conscious selection of seeds by the early farmers? And how similar were the domestication processes for different regions, and for different groups of crops?

The large seeds of many crops compared to their wild relatives are one interesting trait. Researchers have suggested various explanations, including that planted seeds were buried deeper, leaving larger seeds better able to reach the surface after germinating. By germinating the seeds in controlled conditions, I'll be able to assess the size of this advantage.

Legumes, or pulses, will be a particular focus of the project. They are nutritionally important, producing protein from nitrogen fixed by symbiotic bacteria in their roots. In most regions where agriculture began, at least one legume was domesticated, making them a useful group for comparisons.

Selected References

Allaby, R.G., Fuller, D.Q. & Brown, T.A., 2008. The genetic expectations of a protracted model for the origins of domesticated crops. Proceedings of the National Academy of Sciences, 105(37), 13982-13986.

Brown, T.A. et al., 2009. The complex origins of domesticated crops in the Fertile Crescent. Trends in Ecology & Evolution, 24(2), 103-109.

Cunniff, J., 2009. The roles of atmospheric carbon dioxide and plant ecological traits in the origins of agriculture (PhD Thesis). University of Sheffield.

Fuller, D.Q., 2007. Contrasting Patterns in Crop Domestication and Domestication Rates: Recent Archaeobotanical Insights from the Old World. Annals of Botany, 100(5), 903-924.

Hillman, G. et al., 2001. New evidence of Lateglacial cereal cultivation at Abu Hureyra on the Euphrates. The Holocene, 11(4), 383-393.

Morrell, P.L. & Clegg, M.T., 2007. Genetic evidence for a second domestication of barley (Hordeum vulgare) east of the Fertile Crescent. Proceedings of the National Academy of Sciences, 104(9), 3289-3294.

Purugganan, M.D. & Fuller, D.Q., 2009. The nature of selection during plant domestication. Nature, 457(7231), 843-848.

Richerson, P.J., Boyd, R. & Bettinger, R.L., 2001. Was Agriculture Impossible during the Pleistocene but Mandatory during the Holocene? A Climate Change Hypothesis. American Antiquity, 66(3), 387-411.

Weiss, E., Kislev, M.E. & Hartmann, A., 2006. Autonomous Cultivation Before Domestication. Science, 312(5780), 1608-1610.