The Domestication and Exploitation of Plants and Animals

G. W. Dimbleby

• Publisher: Routledge
• Year: 2017
• Print ISBN: 9781138535237
• eBook ISBN: 9781351483421
• Topic: Social Sciences
• Subtopic: Anthropology
• Index: Social Sciences

The domestication of plants and animals was one of the greatest steps forward taken by mankind. Although it was first achieved long ago, we still need to know what led to it and how, and even when, it took place. Only when we have this understanding will we be able to appreciate fully the important social and economic consequences of this step. Even more important, an understanding of this achievement is basic to any insight into modern man's relationship to his habitat. In the last decade or two a change in methods of investigating these events has taken place, due to the mutual realization by archaeologists and natural scientists that each held part of the key and neither alone had the whole. Inevitably, perhaps, the floodgate that was opened has resulted in a spate of new knowledge, which is scattered in the form of specialist reports in diverse journals.

This volume results from presentations at the Institute of Archaeology, London University, discussing the domestication and exploitation of plants and animals. Workers in the archaeological, anthropological, and biological fields attempted to bridge the gap between their respective disciplines through personal contact and discussion. Modern techniques and the result of their application to the classical problems of domestication, selection, and spread of cereals and of cattle were discussed, but so were comparable problems in plants and animals not previously considered in this context.

Although there were differing opinions on taxonomic classification, the editors have standardized and simplified the usage throughout this book. In particular, they have omitted references to authorities and adopted the binomial classification for both botanical and zoological names. They followed this procedure in all cases except where sub-specific differences are discussed and also standardized orthography of sites.

Part I: Origins of domestication

Section 1: Environmental background

David R. Harris

Agricultural systems, ecosystems and the origins of agriculture

Progress in the understanding of plant and animal domestication and the evolution of agriculture depends ultimately upon the accumulation of factual evidence from detailed taxonomic, cytological, palynological and archaeological studies. But it is necessary first to consider the problem of domestication in ecological terms. At best this approach provides a unifying conceptual framework within which to investigate the origins of agriculture and the evolution of all agricultural systems. At the least it provides a means of selecting those topics and areas that call most urgently for detailed study and thereby prevents the dissipation of limited time and resources on arbitrarily-chosen investigations.

The ecological approach requires that we conceive of agriculture as an integral part of the environment in which it is practised. This applies equally to techniques of cultivation and harvesting as to crops and livestock: all may be regarded as components of given ecosystems. Thus we recognize agricultural systems, whether they are forms of primitive, palaeotechnic cultivation or of modern, neotechnic farming, simply as distinctive types of man-modified ecosystems.

The methodological merit of this approach is that it provides a framework for the analysis of agricultural systems by focusing attention on the properties they share with all other systems, i.e. structure, function, equilibrium and change. We are thus led to ask four fundamental questions about each agricultural system: how is it organized ? how does it function ? what degree of stability does it have ? and how did it evolve through time ? There have been few attempts to answer these questions adequately for major agricultural systems of the modern world, such as plantation agriculture, commercial grain farming and commercial livestock ranching, and at present there is insufficient evidence to do so for any of the agricultural systems of the traditional, “non-Western” world. And yet it is the study of traditional agricultural systems, such as shifting or “swidden” cultivation, fixed-plot horticulture, wet-padi cultivation, nomadic pastoralism and forms of mixed grain-livestock farming, that yields the most valid insights into the origins of agriculture. In what follows the relations between agricultural systems and natural ecosystems are explored as a prelude to deductions about the ecological and cultural conditions most likely to give rise to domestication and the initiation of agriculture. These inferences are put forward as an invitation to enquiry and no attempt is made here to test them against the available “facts”¹.

Agricultural systems and ecosystems

In the study of major natural ecosystems at a regional scale a fundamental distinction can be made between generalized and specialized types². The generalized ecosystems are characterized by a great variety of plant and animal species each of which is represented by a relatively small number of individual organisms. Thus the diversity index of the ecosystem—or the ratio between numbers of species and of individuals—is high. Conversely specialized ecosystems have a low diversity index and are characterized by a small variety of species, each of which is represented by a relatively large number of individuals.

In generalized terrestrial ecosystems net primary productivity, or the increment of plant material per unit of time, tends to be high and many ecological niches are available to species at all trophic levels in the food web, from the primary producers (green plants) to the primary, secondary and tertiary consumers (herbivores, carnivores and top carnivores) to the decomposers (macro-organisms such as worms and woodlice and microscopic protozoa, fungi and bacteria). The structural and functional complexity of generalized ecosystems results in their having greater stability, or homeostasis, than specialized ecosystems. Thus the reduction or removal of a component species, whether by natural or human agency, tends to have less effect because alternative pathways for energy flow are available within the system. When alternative food sources exist for many species at each trophic level, population levels fluctuate less widely and changes in one component are less likely to trigger off a sequence of interactions affecting the whole ecosystem. The tropical rain forest is the most highly generalized, productive and stable of major terrestrial ecosystems. It has the highest diversity index, and, although there are very few precise measurements available, net primary productivity of above-ground plant parts reaches 10-20 grams per square metre per day (c. 3600-7200 gm/m²/yr)³.

By contrast specialized natural ecosystems are much less productive and tend also to be less stable. Among the most specialized of major terrestrial ecosystems are the tundra, the average annual above-ground primary productivity of which is less than 1 gm/m²/day, although during the brief growing season it may rise to 4 gm/m²/day; the mid-latitude grasslands, whose average annual primary productivity ranges from about 0-5 to 2 gm/m²/day; and the boreal forest, with average annual primary productivity of up to about 2-5 gm/m²/day. There is not always an inverse relationship between the degree of specialization of an ecosystem and its productivity—for example, desert ecosystems are characteristically more generalized than tundra, grassland or boreal forest ecosystems and yet their average annual primary productivity is usually less than 05 gm/m²/day—but there is nevertheless a general tendency for primary productivity to be higher in the more generalized ecosystems. Certainly a gradient is apparent in major forest ecosystems from the most highly generalized and productive type, the equatorial evergreen rain forest; through the tropical seasonal semi-evergreen and deciduous forests, where species diversity is less and growth limited by a dry season the length and intensity of which increases with latitude; to the more specialized and less productive mid-latitude temperate deciduous and evergreen forests where growth is checked by winter cold.

It is both valid and illuminating to extend this method of analysing natural ecosystems to the interpretation of agricultural systems. It is at once apparent that most modern, neotechnic agricultural systems are highly specialized; they exist to produce maximum numbers of optimum-sized individuals of one or two preferred plant or animal species. Some traditional, palaeotechnic agricultural systems are similarly, if rather less highly, specialized. Wet-padi cultivation and nomadic pastoralism are both dependent on a very limited range of domestic crops and livestock and have evolved special techniques for raising them and for maintaining the productivity of the system (periodic flooding of the rice on the one hand and seasonal migration of the herds on the other). Many traditional agricultural systems, however, are more generalized. They are polycultural rather than monocultural, raising a diverse assemblage of crops in functional interdependence and sometimes integrating livestock into the system as both consumers and fertilizing agents. Shifting swidden cultivation and fixed-plot horticulture are examples of such generalized systems still widely practised in the tropics, while in mid-latitudes mixed farming—involving the production on the same land of crop combinations of grains, roots and livestock—represents a somewhat less generalized system which has become more specialized by reaching a higher level of technical complexity.

From this comparison between natural ecosystems and agricultural systems three principal ways in which the advent of cultivation changes natural ecosystems can be deduced. The mode of change most apparent today is when more or less generalized natural ecosystems have been transformed into specialized artificial ecosystems. This involves a drastic reduction in the diversity index following replacement of most of the wild species of the ecosystem by a relatively small complement of cultivated plants and domestic animals. The transformation may also lead to the selective increase of certain wild species that thrive in the disturbed habitats associated with cultivation and settlement, i.e. both plant and animal “weeds”, but by the build-up of their populations at the expense of more vulnerable members of the natural community, the specialized nature of the ecosystem is enhanced and the diversity index remains low. The transformation of generalized natural ecosystems into specialized agricultural systems usually leads to a loss of net primary productivity, but this is not always so. Under modern methods of intensive farming the trend may be reversed. The productivity of sugar cane under intensive cultivation in Hawaii (6700 gm/m²/yr) falls within the upper range of estimates already quoted for the tropical rain forest; and that of a fertilized maize field in Minnesota was found to be approximately equal to the annual net primary productivity of a nearby deciduous oak wood which had been protected from exploitation⁴.

The second mode of change—the transformation of specialized natural ecosystems into more generalized agricultural systems—has happened only rarely. The introduction into areas of mid-latitude grassland of a crop-livestock-weed complex associated with a system of mixed farming, as occurred for example during the nineteenth century on the American prairie and the Argentinian pampas, probably resulted in an increase in diversity index, as has the establishment of polycultural irrigation agriculture in certain desert ecosystems in the twentieth century. But in so far as agriculture has intruded into specialized natural ecosystems, and it is of course effectively absent from the boreal forest and the tundra, then it has tended to do so by replacing the natural ecosystem with monocultural cultivation, such as cereal dry-farming or cotton irrigation, resulting in a lowering of the diversity index.

Thirdly, the agricultural utilization of a natural ecosystem may be accomplished by manipulation rather than transformation; not by drastically changing its diversity index but by altering selected components without fundamentally modifying its overall structure. Instead of an artificial ecosystem being created to replace the natural one, cultivation may proceed by substituting certain preferred domesticated species for wild species that occupy equivalent ecological niches. Thus an assemblage of cultivated trees and shrubs, climbers, herbs and root crops may take over spatial and functional roles essentially similar to those fulfilled by wild species of equivalent life-form in the natural ecosystem. Swidden cultivation and fixed-plot horticulture manipulate the generalized ecosystems of tropical forests in this way and in so doing come closer to simulating the structure, functional dynamics and equilibrium of the natural ecosystem than any other agricultural systems man has devised. The substitution for equivalent wild species of domestic animals rather than crops occurs less frequently in manipulated ecosystems. Certain domesticates—notably dogs and pigs—may fulfil a role as scavengers, but this function is normally confined to the immediate...

Table of contents

• Cover
• Title Page
• Copyright Page
• Contents
• Preface
• List of Participants
• Context and development of studies of domestication
• On co-operation
• PART ONE Origins of Domestication
• PART TWO Methods of Investigation
• PART THREE Regional and local evidence for domestication
• PART FOUR Studies of particular taxonomic groups
• PART FIVE Human nutrition
• CONCLUSION
• General Index
• Index of Sites and Localities
• Index of Authors
• The plates are between pp. 550 and 551