Plant 249

Hordeum vulgare L. (Poaceae)



For millennia, people have grown and traded barley, whilst its domestication may be one of the foundations of western civilisations. Domesticated barley is thought to have originated in the Fertile Crescent, where its wild ancestor is common.

The Fertile Crescent extends in a long arc from the Red Sea north along the eastern Mediterranean into northern Syria before sweeping east through southern Turkey and then southeast along the Iraq-Iran border.

Domestication is a dynamic process where heritable genetic changes are established in a group of plants through their interactions with us. Through domestication, wild plants are transformed into crops with altered morphologies, anatomies, physiologies and chemistries. Eventually, domesticated plants become dependent on us; they can no longer compete with other species outside cultivation.

The first evidence of domesticated barley comes from archaeological sites near Jericho that are up to 8,000 years old. However, Tibet, where barley has been a staple since the fifth century CE, is also a major area of barley domestication. In barley heads, flowers are arranged in threes, with one or three flowers of each triplet being fertile. This means domesticated barley ears are either two- or six-rowed; wild barleys are two-rowed. Wild and domesticated barleys can be separated from each other since mature fruits are retained on the ears of domesticated barley.

In western civilisations, barley has mainly been used for making bread, beer and spirits and animal feed. As a food, barley is considered inferior to wheat. Yet it has been widely grown across Europe since it is productive in dry, nutrient-poor environments where salinity may be an issue; wheat is much less tolerant of such conditions. Six-rowed barley is better for animal feed than two-rowed barley since it tends to contain more protein and less sugar.

The ability of humans to brew alcohol has been argued to be a key innovation for the development of civilisations through our ability to manipulate the natural world and preserve food. Humans have manufactured ethanol for millennia; in the Zagros Mountains, Iran, traces of barley beer have been found on pottery fragments at least 5,000 years old. Numerous Sumerian cuneiform tablets record details of brewing techniques and barley transactions, whilst funerary objects from Egyptian tombs portray the transformation of barley into beer.

Brewers have exploited differences between barley types, with two-rowed barley being traditionally used for English and German ales, and six-rowed being used for American lager beers.

Further reading

Dai F et al. 2012. Tibet is one of the centers of domestication of cultivated barley. Proceedings of the National Academy of Sciences of the United States of America 109: 16969-16973.

Murphy D 2007. People, plants & genes. The story of crops and humanity. Oxford University Press.

Zohary D et al. 2013. Domestication of plants in the Old World. Oxford University Press.

Stephen Harris