Back to the Future – from the early history of wheat domestication.

Out of all the world’s wheat species Bread wheat has predominated and 95% of the world’s wheat production is now bread wheat. Bread wheat originated around 9,000 years ago near the Caspian Sea after farming had started.

Durum wheat used for pasta is the second most important species making up nearly 5% of global production. Its flour has great binding properties needed to keep pasta intact when cooked in water. Other species of wheat that were once important such as emmer, einkorn, spelt and rivet wheat are grown on a small-scale and some have niche markets. Other types of wheat which may have been important in the past have become extinct over the course of history.

Origins of human use of wheat.

Communities living in the Fertile Crescent at the eastern end of the Mediterranean Sea (this includes modern-day south-eastern Turkey, Syria, Iraq, Lebanon, Jordan, Israel, Palestine and the western fringes of Iran) were fortunate in having access to a range of annual wild grasses and legumes with seeds rich in protein and carbohydrates as food. They gathered these along with seeds, berries and tubers from a range of trees and bushes (such as oak and pistachio species), bulbs and other wild plants, growing in the local landscapes which included woodland park landscapes.  Populations of grains and legumes varied through the region, they weren’t necessarily all together and time and climatic change has altered the distribution of our ancestors of modern-day wheat. Some of these annuals were later to form the ‘founder crops’ of agriculture in the Near East. These include emmer wheat and einkorn wheat, barley, peas, chick peas, lentils, linseed, vetch and some believe possibly rye. The wild ancestor of faba beans are among the other wild plants eventually to feature in agriculture.

First steps in the wheat story

In the beginning among the wild grasses growing in the Fertile Crescent was einkorn which has (two sets of Chromosomes in its nucleus) at some point in pre history it naturally outcrossed with a wild goat grass species Aegillops speltoides.  This resulted in the production of emmer wheat with (four sets of chromosomes ‘A’ and ‘B’ building blocks (DNA) inherited from einkorn wheat and the goat grass). This probably occurred long before humans were gathering these grains around 360,000 years ago. Some genetic studies suggest it may have occurred in the vicinity of Mount Hermon on the Syria Lebanon border and the River Jordan catchment.

Earliest signs of wild wheat use.

One of the earliest pieces of evidence for humans using wild wheat as food comes from the archaeological charred remains of some round brush wood huts from a site called Ohalo II dating from around 19,000 years ago found near the Sea of Galilee. Archaeological evidence suggest that communities already used sickles, digging sticks, querns, pestles and mortars before cultivation techniques were developed and they beat ripe ears into a basket.

Because of the abundance of wild food many settlements developed near to water and communities in the Fertile Crescent became sedentary. From an archaeological stand point if these settlements endured later they developed into mounds or Tel’s in the landscape formed from generations of clay buildings that were flattened and rebuilt.

From gathering to cultivation of wild cereals about 12,000 to 10,700 years ago

Interpretation of how agriculture started in the Fertile Crescent has been a slowly evolving in recent years from an agricultural ‘revolution’ to more of an evolving process that may have happened at many different sites more slowly, rather than one or two. It appears likely that hunter gatherer’s observed the natural cycles and may have started to encourage the growth of food plants such as wild einkorn and emmer wheat by managing the environment around them.  This was possibly stimulated as a result of competition for resources from growing human populations.  Archaeobotanists can detect changes in the flora from wild stands to that associated with cultivation by using floatation tank made from old oil drums or similar items that separate charred plant remains from soil and stones.

From first cultivation to the start of domestication around 10,700 – 10,200 years ago

With the exception of maize which underwent complex changes from its wild relative, all the major grain crops including emmer and einkorn wheat species underwent similar processes of domestication including seed heads that no longer shatter when ripe and seeds increase in size. Changes in seed structure associated with domestication have been observed by archaeologists, such as the attachment scar to the stem. No doubt our views of domestication will evolve as more findings come to light. Current evidence suggests that domesticated cereals gradually predominated over wild forms in farmer’s fields over 1,000 years and full domestication may have taken up to 3-4,000 years. This may suggest that farmers were not harvesting their crops before they were fully ripe which would have resulted in domesticated cereals forming the majority of farmer’s stands of cereals earlier. There may have been advantages in having greater diversity in farmers fields to cope with climatic variability and may have been boosted by early farmers restocking their fields with wild seed to compensate for losses.

Einkorn and emmer may well have been domesticated in different parts of the Fertile Crescent. It was suggested that einkorn was domesticated in the Karacadag Mountains in southeast Turkey. There are two species of einkorn that exist today one species Triticum boeticum was domesticated and the other Triticum uratu remained wild but is in the parentage of emmer wheat and bread wheat. Emmer may have been domesticated in different locations such as in the Jordan Valley, South East Turkey and recent findings also suggest near Iran. Some believe that wild emmer was spread to other locations in the Fertile Crescent from the Jordan Valley by human activity. Until around 5,000 years ago emmer was the most important wheat species in Eurasia. Einkorn was a less significant cultivated wheat species – it too declined from about 5,000 years ago, remaining more important in some more extreme mountainous habitats.

Movement of farming to new areas the birth of bread wheat around 8,500 years ago.

Farming and cultivated wheat spread from the Fertile Crescent as time passed in different directions. Emmer predominated – and different forms evolved some of which are now extinct. One of the changes emmer underwent resulted in the development of free threshing forms of tetraploid wheat – the best known example is pasta or durum wheat.  It appears likely that either domesticated emmer or possibly a form of durum wheat crossed with another wild goat grass species Aegilops taschii possibly in Armenia south-west of the Caspian Sea.  This may have happened successfully a just a few times resulting in the formation of the first forms of bread wheat. These few important natural crosses produced hexaploid plants containing the A and B genome from Emmer or Durum wheat and the D genome from the goat grass Aegilops taschii providing important traits for bread making quality, adaptability and pest and disease resistance. It had been suggested that this resulted in a hulled spelt wheat that quickly evolved into bread wheat. However the archaeological evidence for this hasn’t been found and it appears that the modern-day spelt wheat we know in Europe may have resulted much later from a back cross between bread wheat and Emmer in the Eastern part of European Mediterranean.

Back to the future.

Because these natural crosses between emmer or durum wheat and the goat grass Aegilops taschii happened so rarely the diversity of the D genome in bread wheat has been somewhat limited.  Breeders in recent years have increased the diversity of the D genome in bread wheat by recreating those first chance natural crosses that resulted in the formation of bread wheat by using different forms of Aegilops taschii from across its natural range.  The results of these ‘synthetic hybrids’ or re-synthesised wheat may shed light on what early farmers saw in their fields and the reason why bread wheat took a while to predominate. The synthetic hybrids are difficult to produce and require embryo rescue to help them on their way. Farmers would have seen bigger plants in their fields which must have had some good attributes for them to be maintained but may be there were also poor agronomic problems that took time to unravel. It appears from modern crosses even when free threshing durum wheat is used as a parent the progeny may be initially hulled. Nowadays these crosses are first steps – or Pre Breeding step – in introducing valuable characteristics from the goat grass Aegilops taschii into bread wheat varieties of the future.  CIMMYT (The International Maize and Wheat Improvement Centre) in Mexico and NIAB (the National Institute of Agricultural Botany) in the UK are among the institutes involved in these breeding programs.   Similar crossing programs have also been developed to increase diversity in bread wheat using a range of wheat wild relatives at the University of Nottingham in the UK.

References

Civan. P, Ivaničová. Z., Brown T. (2013) Reticulated Origin of Domesticated Emmer Wheat Supports a Dynamic Model for the Emergence of Agriculture in the Fertile Crescent Plos One http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0081955

Fuller D.Q., Asouti E, Purruganan M.D. (2012) Cultivation as slow evolutionary entanglement: comparative data on rate and sequence of domestication. Vegetation History and Archaeobotany 21 131-145

Fuller D.Q., Willcox G., Allaby R.G.(2011) Cultivation and domestication had multiple origins: arguments against the core area hypothesis for the origins of agriculture in the Near East, 628-652. In World Archaeology 43 (4)

Fuller D.Q., (2010). An Emerging Paradigm Shift in the Origins of Agriculture Institute of Archaeology, University College London. Bulletin of the General Anthropology Division. Vol 17 No.2

Harlan J.R., Zohary D. (1966) Distribution of Wild Wheats and Barley. Science Vol. 153 no. 3740 pp. 1074-1080

Heun M. et al. (2012) A critical review of the protracted domestication model for Near-Eastern founder crops: linear regression, long-distance gene flow, archaeological, and archaeobotanical evidence. J. Exp. Bot. http://jxb.oxfordjournals.org/content/early/2012/06/15/jxb.ers162.full#ref-20

Hillman G.C. pers. com.

Nesbitt M. (1998) Where was Einkorn Domesticated? Trends in Plant Science Research Notes. Volume 3 No. 3 82-83

Peng J.H., Sun D., Evo N. (2011) Domestication evolution, genetics and genomics in wheat. Mol Breeding 28:281–301

Rheil S. (2013) Emergence of Agriculture in the Foothills of the Zagros Mountains of Iran Science Vol. 341 no. 6141 pp. 65-67

Shewrey P. (2009) Wheat Journal of Experimental Botany Vol 60 (6) 1537-53

Willcox G. (2012). The beginnings of cereal cultivation and domestication in Southwest Asia. In D. Potts (ed.) A companion to the archaeology of the ancient Near East. 163-180. Blackwell

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About cornucopiaalchemy

Dr. Andrew Ormerod has 14 years experience working as the Economic Botanist at the Eden Project - researching topical stories, artefacts, ethnobotanical inks, catering and retail links to exhibits. Previously I was involved with plant breeding and plant tissue culture working on a range of crops including winter cauliflowers, agricultural lupins, vining peas, wheat and barley and coconuts. I am now freelance and am interested in opportunities for lecturing; writing articles; consultancy linked to development of botanic gardens for crops based exhibits; supply chain work for unusual food or non-food crops with interesting stories about plants and people attached to them.
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