In this chapter, we discuss the evolution of domesticated plants in the periods subsequent to the episode of domestication. We unfold the influences of domestication on the genetic variability of different crops and trace the evolutionary forces that promote genetic diversification and its preservation over the years. At the same time, we also identify forces that restrict genetic diversity among the different domesticated crops. We end this chapter by reviewing the impact of these processes on current and future plant breeding and endeavours for crop improvement.

This book is about plant domestication and the origins of agriculture in the Near East (Figure Introduction 1), which were major components of the process known as the Agricultural Revolution or the Neolithic Revolution.1 The expansive discussion we offer in this book is restricted to plant domestication; animal domestication, a broad subject in its own right, is treated in a contribution by Professor Gila Kahila Bar-Gal (see Chapter 14). The term ‘domestication’ (or ‘plant domestication’) in the context of the current work carries both biological and cultural significance. From the biological perspective, it implies the acquisition of new traits that differ from the prevalent wild type plant while the cultural perspective denotes a change in worldviews and life-ways enabling the adoption of plants for food production. Throughout this book we distinguish between the Agricultural Revolution (see Glossary, General Terms, Agricultural Revolution) as a general socio-cultural transformation and the domestication (see Glossary, General Terms, Plant domestication) of plants (and animals) as a single aspect of this multifaceted human development.

The Fertile Crescent, named so after its lunate silhouette, spans from Khuzestan Province in Iran, across the Zagros Mountains in western Iran (Kurdistan), to the river valleys of the Euphrates and Tigris in Iraq, south-eastern Turkey and northern Syria, and then westwards towards Lebanon, the Mediterranean zone of Israel and Jordan and finally spanning southwards towards the Nile (see Figure Introduction 1). Geologically, most of the Fertile Crescent is covered by rocks that were formed at the bottom of the Tethys Ocean millions of years ago and soils that eroded from these rocks. Additional geological formations include extensive basalt flows characterized by the fertile soils they generate, outcrops of igneous rocks such as granites that are hundreds of millions of years old, and the sandstone deposits formed in the coastal areas of the ocean mostly during the Lower Cretaceous. Valleys of the region are characterized by deep alluvial soils and colluvial deposits from mountains, especially after humans cut down forests, thereby accelerating soil erosion. The coastal plains of the eastern Mediterranean are characterized by low ridges of beach-rocks (kurkar, solidified dunes), sandy loam soils (ḥamra) and dunes originating from quartz particles that eroded from the granite rocks of East Africa, and which were transported to the Mediterranean by the Nile and pushed further to the eastern coast of the Mediterranean by sea currents.

We introduce this chapter with a partial discussion of the conceptual framework that underlies the research on the Agricultural Revolution (Glossary, General Terms, Agricultural Revolution). We first explain how hunter-gatherers gained their knowledge and put it to use. We then present key ideas that have been offered throughout the years to explain the advent of the Agricultural Revolution. Many researchers have attempted to answer the question of why the Agricultural Revolution occurred. Some answers are broad, driven by a perception that human action is a reaction to some external force(s). Others emphasize the social dynamics that might have led to this revolution. Most of these explanations were formulated during the last half of the twentieth century. To facilitate a better understanding of these views, we will elaborate on prevalent research perceptions regarding plant domestication (Glossary, General Terms, Plant domestication), which was central to the Agricultural Revolution.

Similar to wild populations, traditional landraces (varieties, cultivars) of many annual crops form dynamic populations, the genetic make-up of which changes over time. This point was clarified in our earlier discussion (Chapter 5, and see Chapters 8, 9) on the changing incidence of early and late bloomers responding to seasonal rainfall among both wild populations and cultivated plants. Usually, traditional farmers would preserve sowing materials from the last yield of traditional cultivars (see Glossary, Botany, Ecology and Agronomy, Traditional cultivar (landrace)), which comprise a sample of sorts of the entire yield. The population make that farmers thus own reflects the historical evolution that occurred in their fields. This includes natural selection originating in pressures caused by agents such as pest and disease epidemics, extreme climate, frequently occurring random mutations and the farmers’ own selection processes when choosing the plants or plots in their fields from which seeds will be cached for the next season. Since traditional landraces are dynamic, it would be unreasonable to assume that all of the differences found between the progenitors of the founder crops and the domesticated types are solely the result of the pristine domestication episode. In other words, some of the differences between these two plant groups are the results of selection processes that took place during the thousands of years that have elapsed since domestication and under (a cultivation regime) domestication.

In this chapter, we discuss the questions of where and when Near Eastern plant domestication occurred: Did it transpire in a single, defined area, or perhaps it took place in different areas across the entire Fertile Crescent? Was each crop domesticated separately, or perhaps several crops were domesticated together as a harmonious agricultural package, in which crops complement each other nutritionally and agronomically? Was each crop domesticated on several occasions, each in a separate location, or did each crop undergo a single domestication episode? We look into evidence for each of these questions, based on several fields of knowledge, including geobotany, archaeology, archaeobotany and genetics – some of which we touched upon in earlier chapters. Finally, we examine whether the picture that emerges through these combined lines of evidence allows us to trace the progression of the new, agriculturally based economy throughout the Near East and from there to Europe, Asia and Africa.

In this chapter, we bring together most of the aspects discussed earlier, including biological, agricultural-agronomical and cultural facets related to plant domestication and the roots of Near Eastern agriculture. We briefly describe the spread of domesticated plants and the institutionalization of the agricultural system while discussing the historical and conceptual component underlying the Agricultural Revolution. Finally, we return to our lead question of why the Agricultural Revolution transpired.

Scientists generally agree that fruit trees were domesticated several millennia after the domestication of grain crops. And just as there is a founder group of grain crops, there is also a founder group of fruit trees. It is generally believed that the olive, fig, grape vine, date palm and pomegranate (Figure 11.1) were the first trees domesticated in the Near East.

Near Eastern plant domestication, which took place over 10,000 years ago, has become an important research topic worldwide, drawing many researchers from diverse disciplines. For us, who live in the area, it is only natural that we focus our attention on it. Plants domesticated in other world regions also contribute important elements to key food packages. In this chapter, we discuss plant domestication centres found in Africa, East Asia and America.

In this chapter, we discuss the difference between wild and domesticated plants, focusing on those crops (wheat, barley, lentil, pea, chickpea and flax) that were domesticated in the Near East during the Neolithic period. We first review the traits that endow wild plants with selective advantage (increased fitness) in their natural habitats and then we look at domesticated plants through the prism of that list of traits.

The Agricultural Revolution (which made us all – humans – food-producers) is a major landmark in human history. It reflects a significant transformation in the general organization of human society and its components (see Glossary, General Terms, Agricultural Revolution). Since the advent of humans as tool-makers, some three million years ago, that is, since the moment we began producing tools and using them as a key vehicle in our daily activities, no transformation was as significant as the Agricultural Revolution. After three million years of living in small, mobile communities while subsisting by hunting animals and gathering plant foods, the Agricultural Revolution, which took place post-Pleistocene, during the Neolithic period, just over 10,000 years ago, brought about a prominent transformation in human life-ways. Mostly, it allowed humans to become food-producers, rendering them a unique and singular being on Earth. Small or large sedentary farming villages, characterizing the new way of life in the Near East, soon grew in size to very large villages, also known in Neolithic research as towns,1 which later became cities (Figure 1.1).