Are models for the origins of agriculture in southwest Asia based on a misunderstanding of the relationship between wild and domesticated wheat?

Agriculture is thought to have begun about 10,000 years ago in the 'Fertile Crescent', a region of southwest Asia comprising the plains of Mesopotamia, Syria, Israel, Jordan and Palestine, and some of the mountainous areas to the east of Anatolia. The beginning of agriculture was one of the most important events in the human past, being the first occasion on which humans broke free from the limits imposed by the environment and learnt how to shape the environment to their own ends. Agriculture also had far reaching effects on human society, eventually resulting in rapid population growth and the development of complex civilizations such as those of Classical Greece and Rome. Much research has been devoted to understanding the origins of agriculture but many questions remain unanswered. One of the most important of these is whether the transition from hunting-gathering to agriculture was a rapid or a gradual process. Initially, views on this topic were influenced by experimental studies which showed that if appropriate husbandry practices were applied, then the period required for a wild cereal to undergo the genetic changes associated with domestication might be as short as a few decades. The attractive idea that a single group of enlightened people could have been responsible for the domestication of one or more staple crops within a few human generations was supported by the first comprehensive genetic comparison of wild and cultivated cereals, which was interpreted as indicating a rapid domestication of einkorn wheat in the Karaca Dag region of southeast Turkey. Other genetic studies supported the idea that cereals were domesticated rapidly, but disagreed about exactly where the process took place for individual crops. Archaeological research, on the other hand, has given conflicting evidence suggesting that cereal domestication was a protracted process that took several millennia to complete. So why do different genetic analyses of a single crop give inconsistent results, and why do none of these results agree with the archaeological evidence? One possible, unrecognised factor that might be complicating the genetic studies is that domesticated crops have a reticulate rather than linear relationship with their wild progenitor populations. A linear relationship is where the crop is descended directly from a wild population, whereas reticulation arises when there is cross-hybridization between the crop and various wild populations from which it is not directly descended. We have obtained preliminary evidence that the relationship between wild and domesticated emmer wheat is indeed reticulated. In this new project we plan to obtain more comprehensive genetic data to see if this is in fact the case. The project is important because current models for the origins of agriculture, whether based on genetics or archaeology, tend to assume that the relationship between wild plants and the crop is linear. Demonstrating that the relationship is more complex will therefore change our way of thinking about early agriculture, broadening the range of models that could be considered. One of these new models would be the interesting possibility that early farmers collected wild emmer wheat from different parts of the Fertile Crescent, the most useful features of these different wild plants becoming combined in the crop.

Archaeologists, archaeobotanists and prehistorians interested in the origins of agriculture will benefit from the information that we will provide pertaining to cereal domestication in the Fertile Crescent. A demonstration that reticulation has occurred during the evolutionary history of domesticated emmer would force a reappraisal of current models for agricultural origins, resulting in new paradigms that would influence work on this topic in coming years. Plant geneticists and evolutionary biologists studying the evolution of plants during domestication will benefit from the insights that the project will give into the role of hybridization during the evolutionary history of emmer wheat. Crop breeders will benefit from the more accurate knowledge of the relationships between crops and their wild relatives, which will inform future exploitation of wild resources in modern breeding programmes. The general public, including schoolchildren, will benefit from their ability to engage, via media reports and public engagement, in a project which, because of its underlying foundation in human prehistory, will be of inherent interest to many sectors of the community. The archaeologists, archaeobotanists, prehistorians, plant geneticists and evolutionary biologists with whom we wish to engage are all researchers for whom the normal channels for dissemination of project results will be appropriate. We will ensure that we publish our results in journals that are read by these different communities. We will also engage specifically with the evolutionary biology community through presentation of our initial results at the 2015 Society for Molecular Biology and Evolution symposium. The crop breeding community cannot be engaged via standard academic outputs but the 2016 EUCARPIA (European Association for Research on Plant Breeding) Congress presents an excellent opportunity to engage with a mix of academic and commercial crop breeders, especially the smaller companies who tend to be more interested in novel approaches to breeding. The PI and PDRA will become members of EUCARPIA and will present the initial outcomes of the project at the 2016 meeting. We will take advantage of all those opportunities that occasionally arise to engage with the general public and with schoolchildren. In addition, we will create pages relating to the project in the Children's University of Manchester, write an article on the project for the Manchester Faculty of Life Sciences schools magazine 'Biological Sciences Review', and organise a workshop on crops and DNA for schoolchildren as part of Manchester Science Week in 2016.