Domestication of Wheat and Barley: The First Crops of Farming

The domestication of wheat and barley in the Fertile Crescent, between about 9500 and 8000 BC, gave humanity its first staple crops. Over many centuries, people in the Levant, northern Syria and south-eastern Turkey transformed wild einkorn, wild emmer and wild barley into cereals that depended on farmers to sow them. These grains became the foundation of agriculture across western Asia, Europe and North Africa, and their descendants still feed billions of people today.

The wild ancestors

All three crops descend from wild grasses that still grow in the Near East. Wild einkorn grows on rocky slopes from the Balkans to Iran, wild emmer has a narrower range in the Levant and south-eastern Turkey, and wild barley is widespread across the Fertile Crescent and beyond.

Wild emmer was identified in nature only in 1906, when the agronomist Aaron Aaronsohn found it growing near Rosh Pinna in Upper Galilee. His discovery confirmed that the ancestor of cultivated wheat was a native of the Near East.

Wild cereals are surprisingly productive. In 1966 the American botanist Jack Harlan harvested wild einkorn on a hillside in south-eastern Turkey using a flint-bladed sickle. He gathered about a kilogram of clean grain an hour and calculated that a family could collect more grain in three weeks than it could eat in a year. Such yields help explain why foragers invested so heavily in wild cereals long before farming.

Harvesting before farming

People gathered wild cereals for many thousands of years before domesticating them. At Ohalo II, a submerged camp on the shore of the Sea of Galilee dated to about 23,000 years ago, archaeologists found the remains of wild barley and wheat, along with a grinding stone bearing starch grains. Some researchers have argued that weeds among the finds point to small-scale trial cultivation, though this is debated.

From about 12,500 BC, the Natufian culture of the Levant harvested wild cereals intensively, using sickles with flint blades and stone mortars and grinding slabs. At sites such as Abu Hureyra on the Euphrates, plant remains show people turning to cereals and other seeds as the climate fluctuated.

From cultivation to domestication

Archaeobotanists distinguish between cultivation, which means deliberately sowing and harvesting plants, and domestication, which means genetic changes that make plants dependent on people. In the Pre-Pottery Neolithic A, from around 9500 BC, people at sites such as Jericho, Netiv Hagdud, Jerf el Ahmar and Tell Aswad were cultivating cereals that were still wild in form.

Storage was part of this change. At Dhra’ in Jordan, raised-floor granaries dated to about 9300 BC were built between houses to keep grain dry and safe from pests. Over the following centuries, sowing harvested seed year after year gradually selected for plants better suited to cultivation.

The mechanism was largely unconscious. When people harvested ripe stands with sickles or by uprooting, the seeds that stayed on the plant were more likely to be collected than those already scattered on the ground. If part of that harvest was sown the following year, the rare plants with tough, non-shattering ears became slightly more common in each generation. Sowing in prepared, cleared ground also favoured seeds that germinated quickly and grew strongly, which tended to be larger ones. No early farmer needed to understand heredity for these changes to take place.

Cultivated fields could also be moved beyond the natural habitats of the wild plants. Finds of cereals at sites far from their wild ranges, such as Tell Aswad near Damascus, are one of the clues archaeologists use to recognise early cultivation.

The domestication syndrome

Plant scientists call the set of traits that distinguishes crops from their wild relatives the “domestication syndrome”. For cereals, the most important are:

• Non-shattering ears: In wild wheat and barley the ear, or spike, breaks apart when ripe, scattering the seeds. In domesticated forms a mutation keeps the seeds attached to a tough central stalk, the rachis, so they can be harvested.
• Larger grains: Domesticated cereals have bigger, plumper grains.
• Loss of dormancy: Wild seeds germinate unevenly over months or years; crop seeds sprout together when sown.
• More uniform ripening: Plants in a field ripen at the same time.

The tough rachis left a clear signature in the archaeological record, because the base of each ear segment breaks differently in wild and domestic plants. By counting these fragments, researchers can measure how quickly domestication advanced.

How fast was it?

Experiments and models by Gordon Hillman and Stuart Davies, published around 1990, suggested that under strong selection, for example harvesting with sickles when the crop was nearly ripe, a field of wild einkorn could become fully domesticated in as little as 20 to 200 years.

The archaeological evidence tells a different story. A study by Ken-ichi Tanno and George Willcox, published in 2006, showed that domestic-type ears rose only slowly as a proportion of the harvest at sites in Syria and Turkey. Most researchers now accept a “protracted” model, in which fully domesticated wheat and barley took perhaps two to three thousand years to replace wild forms. Domestic-type einkorn, emmer and barley were present by around 8500-8000 BC at sites such as Çayönü, Nevalı Çori and Jericho, but they became fully dominant only over the following millennium or more.

Einkorn, emmer and barley

Einkorn (Triticum monococcum) is a diploid wheat, with two sets of chromosomes and usually one grain per spikelet, which gives it its German name, “one grain”. In 1997 a team led by Manfred Heun compared the DNA of hundreds of einkorn lines and found that cultivated einkorn is most closely related to wild populations in the Karacadağ mountains of south-eastern Turkey, close to Göbekli Tepe.

Emmer (Triticum dicoccum) is a tetraploid wheat, with four sets of chromosomes. It became the most important wheat of the early Near East and of ancient Egypt. Genetic studies also link its domestication to south-eastern Turkey, though some scholars argue for several centres. Emmer later gave rise to durum wheat, used today for pasta.

Einkorn and emmer are both “hulled” wheats: their grains stay tightly enclosed in husks after threshing and must be pounded or parched to free them. They remained important for thousands of years. Einkorn was identified among the food remains in the gut of Ötzi the Iceman, who died in the Alps about 5,300 years ago. Free-threshing wheats, whose grains fall out easily, gradually replaced them in most regions.

Barley (Hordeum vulgare) is hardier than wheat, tolerating poorer and saltier soils and drier conditions. Genetic research published in 2015 showed that the non-shattering trait in barley arose through mutations in two different genes, which suggests that barley was domesticated at least twice, in different parts of the Fertile Crescent. Barley exists in two-row and six-row forms and was widely used for bread, porridge, animal feed and beer. Hulled and naked (free-threshing) varieties both appear in early Neolithic sites.

Wheat and barley were not domesticated alone. They formed part of a package with lentil, pea, chickpea, bitter vetch and flax, which the botanist Daniel Zohary called the founder crops. Legumes added protein and restored nitrogen to the soil, and flax provided fibre and oil, making the package a balanced basis for farming life.

Bread wheat

Modern bread wheat (Triticum aestivum) did not exist at the start of farming. It arose when a cultivated tetraploid wheat crossed naturally with a wild goat grass, Aegilops tauschii, probably in the region south-west of the Caspian Sea, around 9,000 to 8,000 years ago. The resulting hexaploid wheat, with six sets of chromosomes, combined the genes of three ancestral species. Its gluten proteins made it ideal for leavened bread, and it eventually became the world’s most widely grown wheat.

Spread and legacy

Wheat and barley spread with farming. They reached Greece and the Balkans around 6500 BC and central Europe with the Linear Pottery culture around 5500 BC, as described in Spread of Farming into Europe. Barley and wheat were grown at Mehrgarh in South Asia by about 7000 BC, and in Egypt by about 5000 BC. Wheat reached China only around 2500 BC.

In the early civilisations of Mesopotamia and Egypt, barley and emmer were the basis of rations, taxes and wages, and barley beer was a daily drink. Today wheat is grown on more land than any other food crop, and barley remains a major crop for animal feed and brewing.

Timeline

• c. 21,000 BC: Foragers at Ohalo II on the Sea of Galilee gather wild wheat and barley.
• c. 12,500 BC: The Natufian culture intensively harvests wild cereals.
• c. 9500 BC: Cultivation of wild-type cereals begins in the Pre-Pottery Neolithic A.
• c. 9300 BC: Granaries are built at Dhra’ in the Jordan Valley.
• c. 8500-8000 BC: Domestic-type einkorn, emmer and barley appear at many sites alongside wild forms.
• c. 7000-6000 BC: Bread wheat emerges from a cross with wild goat grass.
• c. 6500 BC: Wheat and barley reach south-eastern Europe.
• 1906: Aaron Aaronsohn identifies wild emmer near Rosh Pinna.
• 1997: DNA fingerprinting links einkorn domestication to the Karacadağ mountains.

Why it matters

Wheat and barley were the crops that turned foragers into farmers in western Eurasia. Their domestication made possible food surpluses, larger populations and eventually towns and states. The story of how they changed from wild grasses into staples is central to the Neolithic Revolution and to the history of what people eat today.