Bruce D. Smith [HN1]
Science 1998; 279: 1651-1652.
In both biology and archaeology, research into agricultural origins shows increasing long-term promise. On page 1661 of this issue, for example, Hard and Roney (1) present their findings from the Cerro Juanaqueña site [HN2] in Chihuahua, [HN3] Mexico, that provide the latest in a decade-long string of surprises regarding the initial adoption of Mexican crop plants by hunting and gathering societies in the southwestern United States and northern Mexico and the subsequent development of agriculture in the region. In a larger context, research at this site also highlights recent research advances and changing perspectives on agricultural origins worldwide.
The most dramatic recent advances in understanding agricultural origins center on documenting the domestication of individual species. On the biological side, comprehensive genetic profile comparisons have revealed the identity and geographical range of present-day wild progenitor populations of a number of important domesticated plants (2). At the same time, a number of related advances in archaeology and archaeobiology now permit accurate recognition of the temporal and spatial context of the initial domestication of individual species. Flotation technology has vastly improved the archaeological recovery of plant and animal remains. The morphological changes that mark the adaptive syndrome of domestication in seed plants and the age and sex profile changes that reflect human management of newly domesticated herd animals are now reasonably well documented (3). This in turn allows clear recognition of early domesticates in archaeological contexts. In addition, small sample accelerator mass spectrometer radiocarbon dating [HN4], [HN5], [HN6], [HN7] now allows the unequivocal temporal placement of these early domesticates (4).
In tandem, research incorporating these biological and archaeological advances can produce remarkable results. Genetic fingerprinting, [HN8] for example, recently pinpointed the present-day location of the particular populations of wild einkorn wheat [HN9], [HN10] that gave rise to domesticated einkorn. These wild progenitor populations were growing less than 250 km from the site of Abu Hurerya, which has yielded the earliest evidence of initial domestication of this important cereal grain 9500 years ago (3, 5). Similarly, the earliest evidence for the independent domestication of Cucurbita pepo squash [HN11] in eastern North America 5000 years ago comes from the Phillips Spring site in Missouri, [HN12] located less than 60 km north of where populations of its genetically fingerprinted wild Ozark gourd ancestor still grow today (6).
Early harvest. Map of the southwestern United States and Mexico showing
Cerro Juanaqueña in relation to other sites of the same time period, as well as the
Cocopa of the lower Colorado region. [Adapted from (3)]
Studies like these are documenting important landmarks on the developmental landscape that lies between foraging and farming. This "in-between" territory has long been viewed as a processually brief transitional interlude separating the steady-state solutions of hunting-gathering and agriculture. But as research on such "in-between" landscapes continues, they are turning out to be far larger and far more complicated than previously recognized and to hold the promise of many more surprises like Cerro Juanaqueña.
In spite of continuing attempts at simple global explanations for the development of agriculture (such as climatic change, population pressure, El Niño, or the need for feasting foods), it is increasingly evident that societies in different world areas followed diverse developmental pathways leading toward agriculture. In each region, from north China to the southern Andes, different species were sequentially domesticated over quite varied temporal spans and filled a range of dietary roles before eventually being combined into agricultural economies. It is clear too that in many areas of the world the "in-between" developmental landscapes from foraging to farming are extremely large when measured chronologically. In Mexico, for example, a full 6000 years separates the first domesticate (4) from the subsequent initial appearance of village-based farming economies in which domesticates make a substantial dietary contribution. In eastern North America the time span from the first domesticates to agriculture is about 4000 years. In the Near East it is perhaps 3000 years. Clearly, in many world areas the transition from hunting and gathering to agriculture covered a lot of territory, developmentally and chronologically.
Recent research on many of these "in-between" transitional territories also indicates that there is not a solitary processual expressway, broad and straight, leading directly from domestication to agriculture. Rather, in each world area the traces of multiple developmental pathways can be seen, each representing the alternative exploratory journeys of societies working on what were long-term stable solutions to very localized sets of cultural and environmental challenges. Often these solutions also appear to include a prominent role for "in-between" species of plants and animals. Such "in-between" species are the subject of various forms and levels of deliberate human management and life-cycle intervention that extend far beyond simple hunter-gatherer procurement (7). But they do not exhibit any obvious markers of domesticated status and as a result are difficult to recognize archaeologically. Their economic importance can sometimes be indirectly inferred, however, in modifications to the landscape and in the abundant representation of both their remains and the technology used to process them.
Where then does Cerro Juanaqueña fall on this "in-between" landscape, when viewed in terms of these changing perceptions of agricultural origins? The accelerator mass spectrometry dates on maize from the site provide further evidence that when they arrived 3500 to 3000 years ago (1), Mexican domesticates were rapidly adopted by societies developing distinctly localized solutions to different environmental settings across a broad area of the American Southwest. The mass spectrometry dates also suggest that substantial artificial terrace construction occurred over a short period of time. This sets Cerro Juanaqueña apart in terms of population size and the scale of labor investment both from contemporary river valley settlements of the arid Tucson Basin area as well as the seasonally occupied cave sites of the higher elevation Mogollon Highlands and Colorado Plateau (see map). In addition, a number of local nondomesticated seed plants appear to qualify as economically important "in-between" species, on the basis of their abundance and the associated high frequency of ground stone seed processing tools.
In these respects Cerro Juanaqueña adds to the set of alternative developmental pathways from foraging to farming documented for the southwestern United States in the past decade. It also adds to the growing suspicion that when maize and squash were introduced into the region, some southwestern societies were no longer pristine hunter-gatherers but had already established low-level food production economies centered on the management of indigenous "in-between" seed crops (8), and perhaps on as yet unrecognized local domesticates.
The author is in the Department of Anthropology, National Museum of
Natural History, Smithsonian Institution, Washington, DC 20560, USA. E-mail: smith.bruce@simnh.si.edu
PLB143: Evolution of Crop Plants is an outline of a course offered at the University of California, Davis. Detailed lecture outlines provide lists of readings in addition to facts about the domestication of plants with illustrations and tables. Lecture outlines cover lifestyles of hunters and gatherers, methods in the study of crop evolution, and characteristics of crop plants.
Plants, Genes and Global Food Production provides information to accompany a course offered by the Cornell University Department of Plant Breeding. The Index of Course Readings provides links to the full text of selected readings on food crops and their domestication. Readings for Lecture 2, Evolution and Domestication of Food Crops, present discussions of plants, genes, and the emergence of agriculture. Through its Web site, the National Agricultural Library provides a list of Internet resources for agriculture.
The World Wide Web Virtual Library Agriculture is an extensive list of Internet resources for agriculture. This page is maintained by the National Science Foundation Center for Integrated Pest Management, located at North Carolina State University.
The World Wide Web Virtual Library Circumpolar and Aboriginal North America Resources is a list of Internet resources for the study of Native Americans. The Index of Native American Resources on the Internet lists additional resources.