Preface

      Third Edition, 2021

      Since the second edition of Crops and Man was published some 30 years ago, germplasm collections have expanded greatly, molecular genetics has taken root and is being used to answer age‐old questions, and archaeological research has discovered many ancient plant and animal remains, uncovered new sites, and expanded our knowledge of the movement of man and his crops throughout the world. Many of the early studies are no longer possible to continue because hunter‐gatherers have all but disappeared except in a few relatively isolated regions.

      Crop plant evolution involves an understanding of human behavior, as well as extensive knowledge about plants, what happens to plants as man selects traits that he values, and the importance of these plants in varying societies. The process of evolution takes place over both time and space, and as Jack Harlan so eloquently points out, there is no one model or answer to all questions. In this edition, we made every effort to maintain the basic structure of the previous volumes, while updating information that has evolved during the past 30 years. Most of the original references are still used because evolution of particular plants and many theories have not changed, and the older literature presents the foundation for current work.

      Jack Harlan did not formulate his theories and concepts by sitting in an office or library and daydreaming; he explored many regions of the world’s centers of diversity. He collected more than 12,000 accessions of cereals, forages, legumes, trees, and fruits from more than 45 countries. Many of these have been extensively used as the sources for disease and insect resistances and to introduce genetic variability to modern production agriculture. He made taxonomic revisions of the genera Cynodon and Sorghum and studied the evolution of many other species, especially the cereals. He was also involved in archaeological research and had firsthand knowledge of ancient plant types.

Dr. Harlan formulated five concepts as related to crop plant evolution: first, the “Compilospecies” concept where related species intermate to form hybrid swarms with high levels of fitness and aggression, and which are able to expand their ecological range. Secondly, he understood the relationships between crops and companion weeds, and the importance of introgression to maintain diversity in a species. Third, Vavilov’s Centers of Origins, which were more centers of diversity than origin, were revised into larger areas. Dr. Harlan recognized that not all crops had distinct centers and that the center of origin is not necessarily (and is more often not), the center of diversity. Fourth, he understood that the origin of crop domestication occurred for different reasons by various peoples and no one concept fits all situations. Thus, he developed a no‐model model to incorporate the array of theories for crop domestication. Lastly, a natural classification of cultivated plants was proposed that consisted of gene pools rather than the classical method of morphological descriptions. This allows the thousands of variants of a crop to be lumped together into a single genetically and reproductively unified gene pool.

      For his masterful accomplishments and service to the agriculture community, Dr. Harlan received many highly prestigious recognitions and awards, both nationally and internationally. His contributions have been recognized in symposia and in Europe a conference series named after him continues to bring together scientists to discuss topics in crop plant evolution.

      Jack Harlan was a brilliant scientist and a true scholar. He stimulated all those who knew him to explore new avenues of learning and to never stop acquiring knowledge, not only in their specialty, but in related fields as well. Jack R. Harlan was my mentor, graduate advisor, and friend.

      Harlan’s use of the word “man” to describe all people was commonplace at the time of his writing. We have left this gender non‐descript word use in our attempt to maintain the original flavor of his entertaining story style, and trust our readers understand we mean no disrespect.

      In this revision, we hope that young plant scientists will broaden their views of the world around them to better understand the evolution of humans and the plants that feed the world. The book does not present the genetics of speciation, polyploidy, or plant breeding. But rather, it is intended to present views of evolution through the personal experiences of Jack Harlan and set the foundations for patterns of crop diversity.

       H. Thomas StalkerRaleigh, North Carolina

1 Prologue: The Golden Age

       First of all the immortals who dwell on Olympian homes brought into being the golden race of immortal men. These belonged to the time when Kronos ruled over heaven, and they lived like gods without care in their hearts, free and apart from labor and misery. Nor was the terror of old age on them, but always with youthful hands and feet they took their delight in festive pleasures apart from all evil; and they died as if going to sleep. Every good thing was theirs to enjoy: the grain‐giving earth produced her fruits spontaneously, abundantly, freely; and they in complete satisfaction lived off their fields without any cares in blessed abundance.

      Hesiod, eighth century BC(Translated by R. M. Frazer, 1983)

Crop Evolution

      In this book, we shall be dealing with evolution. We shall try to describe the evolution of crop plants from their wild progenitors to fully domesticated races and the emergence of agricultural economies from preagricultural ones. We shall deal with the activities of man that shaped the evolution of crops and that influenced the shaping of crops as human societies evolved. Crops are artifacts made and molded by man as much as a flint arrowhead, a stone axe head, or a clay pot. On the other hand, man has become so utterly dependent on the plants he grows for food that, in a sense, the plants have “domesticated” him. A fully domesticated plant cannot survive without the aid of man, but only a minute fraction of the human population could survive without cultivated plants. Crops and man are mutually dependent and we shall attempt to describe how this intimate symbiosis evolved.

      The word “evolution” means an opening out, an unfolding, a realization of potential as in the opening of a flower or the germination of a seed. It implies a gradual process rather than sudden or cataclysmic events, with each living thing being derived genetically from preceding living things. Evolution as a process means change with time and the changes may be relatively slow or rapid, the time relatively long or short. Thus, the differences brought about by evolution over time may be small or great. As we shall see, some cultivated plants differ very little, if at all, from their progenitors. The same can be said for the evolution of agricultural economies and the sociological changes that have occurred in the process of developing fully agricultural and industrial societies from hunting–gathering systems.

      To develop a degree of understanding of what has happened and what agricultural systems mean to mankind, we need some sort of picture of what life was like before agriculture. We need to establish a baseline from which we can visualize the domestication of

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