In 1855 Alphonse de Candolle challenged his contemporaries to describe and to explain the geographical and historical distribution of economic plants. It was only in the 20th century, however, that ethnobotany, thedirectinterrelationships between human populations and their plant environment, and paleoecology and archaeology could combine to delineate from antiquity the history of economic plant usages, to describe the ecological changes introduced by humans, and to detail the cultural determinants of new plant evolution.The prehistory of plant uses depends upon paleoecological and archaeological data. Pollen and plant macroremains have demonstrated that only during the past 2000 years in North America have humans expanded the number of taxa they used. Ecologically humans have become important agents for transforming the landscape during the same time period in areas where plant food production was practiced. Fire was the principle agent for clearing the land and plant husbandry intensified the disjunction of plant species. Humans, then, became significant ecological and evolutionary factors in the landscape with the introduction of domesticated cucurbits from Mexico in the eastern United States about 5000 years ago. It was not until 3000 years ago that indigenous North AmericanHelianthusandIvawere domesticated and other plants were cultivated and introduced beyond their known ranges. In the Southwest com cultivation started 3000 years ago and spread rapidly as a staple and source of phytogeographical changes. Com-field farming in the past 1000 years by prehistoric Americans created new habitats and had the greatest effect on the geographical distribution of plants. Ethnobotany and its associated discipline, archaeobotany, have brought an indispensible complement to paleoecology and a new dimension to historical phytogeography.
展开▼
