Wheat Domestication

The History and Origins of Bread and Durum Wheat

Wheat Field in Kansas, USA
Wheat Field in Kansas, USA. Debbie Long

Wheat is a grain crop with some 25,000 different cultivars in the world today. It was domesticated at least 12,000 years ago, created from a still-living ancestor plant known as emmer.

Wild emmer (reported variously as T. araraticum, T. turgidum ssp. dicoccoides, or T. dicocoides), is a predominantly self-pollinating, winter annual grass of the Poaceae family and Triticeae tribe. It is distributed throughout the Near Eastern Fertile Crescent, including the modern countries of Israel, Jordan, Syria, Lebanon, eastern Turkey, western Iran, and northern Iraq.

It grows in sporadic and semi-isolated patches and does best in regions with long, hot dry summers and short mild, wet winters with fluctuating rainfall. Emmer grows in diverse habitats from 100 m (330 ft) below sea level to 1700 m (5,500 ft) above, and can survive on between 200–1,300 mm (7.8–66 in) of annual precipitation.

Wheat Varieties

Most of the 25,000 different forms of modern wheat are varieties of two broad groups, called common wheat and durum wheat. Common or bread wheat Triticum aestivum accounts for some 95 percent of all the consumed wheat in the world today; the other five percent is made up of durum or hard wheat T. turgidum ssp. durum, used in pasta and semolina products.

Bread and durum wheat are both domesticated forms of wild emmer wheat. Spelt (T. spelta) and Timopheev's wheat (T. timopheevii) were also developed from emmer wheats by the late Neolithic period, but neither has much of a market today.

Another early form of wheat called einkorn (T. monococcum), was domesticated at about the same time, but has limited distribution today.

Origins of Wheat

The origins of our modern wheat, according to genetics and archaeological studies, are found in the Karacadag mountain region of what is today southeastern Turkey—emmer and einkorn wheats are two of the classic eight founder crops of the origins of agriculture.

The earliest known use of emmer was gathered from wild patches by the people who lived at the Ohalo II archaeological site in Israel, about 23,000 years ago. The earliest cultivated emmer has been found in the southern Levant (Netiv Hagdud, Tell Aswad, other Pre-Pottery Neolithic A sites); while einkorn is found in the northern Levant (Abu Hureyra, Mureybet, Jerf el Ahmar, Göbekli Tepe).

Changes During Domestication

The main differences between the wild forms and domesticated wheat are that domesticated forms have larger seeds with hulls and a non-shattering rachis. When wild wheat is ripe, the rachis—the stem that keeps the wheat shafts together—shatters so that the seeds can disperse themselves. Without hulls they germinate rapidly. But that naturally useful brittleness doesn't suit humans, who prefer to harvest wheat from the plant rather than off the surrounding earth.

One possible way that might have occurred is that farmers harvested wheat after it was ripe, but before it self-dispersed, thereby collecting only the wheat that was still attached to the plant. By planting those seeds the next season, the farmers were perpetuating plants that had later-breaking rachises. Other traits apparently selected for include spike size, growing season, plant height, and grain size.

According to French botanist Agathe Roucou and colleagues, the domestication process also caused multiple changes in the plant that were generated indirectly. Compared to emmer wheat, modern wheat has shorter leaf longevity, and higher net rate of photosynthesis, leaf production rate, and nitrogen content. Modern wheat cultivars also have a shallower root system, with a larger proportion of fine roots, investing biomass above rather than below ground. Ancient forms have a built-in coordination between above and below ground functioning, but the human selection of other traits has forced the plant to reconfigure and build new networks.

How Long Did Domestication Take?

One of the ongoing arguments about wheat is the length of time it took for the domestication process to complete. Some scholars argue for a fairly rapid process, of a few centuries; while others argue that the process from cultivation to domestication took up to 5,000 years.

The evidence is abundant that by about 10,400 years ago, domesticated wheat was in widespread use throughout the Levant region; but when that started is up for debate.

The earliest evidence for both domesticated einkorn and emmer wheat found to date was at the Syrian site of Abu Hureyra, in occupation layers dated to the Late Epi-paleolithic period, the beginning of the Younger Dryas, ca 13,000–12,000 cal BP; some scholars have argued, however, that the evidence does not show deliberate cultivation at this time, although it does indicate a broadening of the diet base to include a reliance on wild grains including the wheat.

Spread Around the Globe: Bouldnor Cliff

The distribution of wheat outside of its place of origin is part of the process known as "Neolithicization." The culture generally associated with the introduction of wheat and other crops from Asia to Europe is generally the Lindearbandkeramik (LBK) culture, which may have been made up of part immigrant farmers and part local hunter-gatherers adapting new technologies. LBK is typically dated in Europe between 5400–4900 BCE.

However, recent DNA studies at Bouldnor Cliff peat bog off the northern coast of mainland England have identified ancient DNA from what was apparently domesticated wheat. Wheat seeds, fragments, and pollen were not found at Bouldnor Cliff, but the DNA sequences from the sediment match Near Eastern wheat, genetically different from LBK forms. Further tests at Bouldnor Cliff have identified a submerged Mesolithic site, 16 m (52 ft) below sea level.

The sediments were laid down about 8,000 years ago, several centuries earlier than the European LBK sites. Scholars suggest that the wheat got to Britain by boat.

Other scholars have questioned the date, and the aDNA identification, saying it was in too good a condition to be that old. But additional experiments run by British evolutionary geneticist Robin Allaby and preliminarily reported in Watson (2018) have shown that ancient DNA from undersea sediments is more pristine than that from other contexts. 

Sources

Format
mla apa chicago
Your Citation
Hirst, K. Kris. "Wheat Domestication." ThoughtCo, Apr. 17, 2018, thoughtco.com/wheat-domestication-the-history-170669. Hirst, K. Kris. (2018, April 17). Wheat Domestication. Retrieved from https://www.thoughtco.com/wheat-domestication-the-history-170669 Hirst, K. Kris. "Wheat Domestication." ThoughtCo. https://www.thoughtco.com/wheat-domestication-the-history-170669 (accessed April 22, 2018).