Book Review: Economic Botany

The first three chapters show the wide subject range needed to discuss agriculture's beginnings. Chapter I describes mythic and religious explanations of how people learned to farm. Agricultural knowledge is almost always pictured as some divine gift associated with instruction in useful arts such as ceramics, in laws, and a rise from savagery. (Strangely only the Bible, in Genesis, depicts it as a curse.) Yet modern hunter-gatherers show a great store of practical understanding of local ecology. They often skillfully manipulate environments to encourage useful plants and animals. In some cases, hunting-gathering was the basis for societies rich in food and material goods. Then why bother to farm? The hypotheses mentioned above about agriculture's origins are given; they are returned to in the last chapter.

Chapter 2 treats processes of domestication in plants and in animals, recollections of Vavilov, the famed Russian ethnobotanist, and the sequence of information for studying crop evolution. Domestication differs from environmental manipulation because it genetically alters the organism. Changes are related to the selective screen" that humans create when they harvest, store, and plant, and to the local environment. These locally adapted "land races" were what farmers grew for most of human history. Modern large-scale planting of genetically uniform material increases yield under good conditions, but permits equivalently large-scale losses under unfavorable ones. For years, Harlan and others have pointed out modern agriculture's vulnerability that could be lessened through more ecologically-based management. Interactions of ancestors, weeds, and domesticates are discussed. Gene transfer from crops to weeds does occur, and poses major agronomic problems in weed and disease control.

Chapter 3 deals with archaeology, dating, and identification. Over the last 30-40 years, archaeology has greatly changed. The amount of information from any one site is greatly increased. Current archaeology reconstructs daily lives and social and environmental conditions. Archaeological teams include botanists, geologists, and other specialists. Wider use of flotation recovers tiny organic debris. Increasingly sophisticated dating and identification techniques are available. Calibration within and among methods and understanding of limitations are better. Archaeological and paleoclimatic data show world climate change at the end of the Pleistocene. Megafaunal loss, coupled with habitat change from ice melt and rising sea levels, may have created conditions under which humans found plant foods more important.

Chapters 4 through 7 discuss agriculture's origins in different world regions. Each chapter starts with description of paleoclimate and biomes from which cultivar ancestors are believed to have come. Archaeological evidence of tools, plant remnants, animal bones, and any associated cultural descriptions are included. Descriptions of general domestication patters and then of individual crops and animals follow. These include possible progenitors, genetics, adaptations, and human uses and customs, including linguistic evidence.

Chapter 4 covers the Near East. Agricultural origins seem to have been fairly concentrated in space and in time, 12,000-11,000 YBP. After discussion of possible source habitats, morphology and genomes for wheats, barley, pulses and flax, Harlan uses the fall of the Old and Middle Kingdoms of Egypt to illustrate "agricultural vulnerability". Written records from the first indicate prolonged drought, while during both times major movements of people and societal collapses occurred, probably indicating regional drought. Likewise, Mesopotamian cuneiform tablets record increases of barley harvest relative to emmer wheat, and then, later drop in barely itself. These are linked to salinization losses. When agriculture works, many more people can be fed than through hunting-gathering. But "famine and starvation are ... integral ... and agricultural systems are fundamentally unstable." (pg. 115).

Chapter 5 treats Africa, where most crop domestication seems more diffuse, extending crops across the savanna of the sub-Sahara region. Sorghum and yams in particular are discussed. In Sorghum, linguistic groups coincide with cultivars. Tropical forests and the East African highlands provide very different environments, and likewise, crops. Decrue agriculture uses seasonal rise and fall of water level and drying of the land. It is common along certain African rivers such as the Nile, and in wetlands. Along parts of the Niger River Delta, the irregularity in timing, extent of innundation, and of drying requires particular skill to estimate available water and to select appropriate crops.

Chapter 6 on the Far East includes China, southeast Asia, the Philippines, Indonesia and the smaller southwest Pacific islands, and India. North China seems to have been a center of origin. Domestication in the other areas seems more dispersed. North China agriculture is based on millets (various Panicum species) and soybean. Millet names in the Indian languages of Sanskrit, Hindi, Bengali and Gujarati all suggest a Chinese relationship. Vegetables found in modern markets, some of which originated outside the region, have been modified or are used in local ways. Examples are snow pea pods, stem lettuce, and swollen, smut-infested stems of wild rice from eastern China's coastal plane. While south China's main crop is annual rice, rice agriculture did not dominate until human population density and societal structures permitted large-scale water control projects. In China this was about 400-3 00 BC; the date for start of intensive agriculture in southeast Asia is unknown. Current images of southeast Asia include huge wet paddies. But much of this is relatively recent, in the last 200-100 years, with construction of modern dikes and drainage. Evidence for agricultural start on many islands has probably been drowned by sea level rise. In India, northern crops are closer to those of southeast Asia.

Chapter 7 discusses the Americas. While the exact time and nature of human migrations may not be clear, people were on these continents long before evidence of agriculture. Plant domestication seems to have been as early or even earlier than in the Old World. In general, the Andean highlands, especially parts of Peru, Bolivia and Columbia, were sites for early domestications, while agricultural starts in Amazonia were more diffuse. Beans, cucurbits and Capsicum peppers usually were the first plants to appear, while maize was later. The genera Chenopodium and Amaranthus were widely domesticated, some types for seed as pseudocereals, and others as vegetables. Some can grow at very high altitudes where even wheat and rye fail. More root and tuber crops were domesticated in tropical America than anywhere else. Of these, potato, manioc and sweet potato are now widely distributed. The latter two have become dietary staples in Africa, parts of Asia and the south Pacific. The presence of toxins in certain potatoes and manioc, and the need to appropriately grow, store and prepare especially manioc, mark the mastery of practical cuisine chemistry. When these ways are forgotten, nutritional problems still arise and pose public health difficulties.

Chapter 8 covers traditional agricultural techniques. The ecological efficiency of slash-and-burn agriculture throughout the world and especially in tropical forests is discussed in more detail, as are problems arising from increasing human population pressures on traditional systems. Tools and techniques for soil preparation and water management are discussed, with some comparison of mechanical traction versus animal traction, along with sowing and reaping, drying and threshing, and storage.

In Chapter 9, the last, Harlan returns to the hypotheses of agricultural origins, elaborates on modern agricultural vulnerability, and states his views on germplasm control and use. He compares the hypotheses to evidence from the different world regions. Various processes fit different regions and situations. Using FAO and USDA figures, Harlan documents world-wide dependence on few crops, each with a narrow genetic base. He views germplasm as a critical resource. Current world politics often place control of its dissemination at a national level. People working with germplasm maintenance or breeding should have free access to base collections and lines developed with public funds, whereas advanced lines developed privately may be proprietary. In Harlan's experience, local cultivators were pleased to share seed. Some local researchers could not store seed and were glad to see it done elsewhere. Harlan finishes with the themes of sharing of food and of the traditions associated with its production.

The nature of interweaving subjects, along with the thematic organization, leads to repeated discussion of certain topics, but with variations appropriate for different geographic areas. Examples are fire use, and selective modification of flora by hunter-gatherers. Furthermore, occasionally within text portions close together, phrases or ideas are repeated. This creates an occasional sense of deja vu, and awkwardness in phrasing. As the book is a distillation of life-work, the text in places reads as if the author were speaking to the readers. This keeps the book accessible to general audience.