The origins of plant domestication in the upper Madeira River basin in lowland South America

点击翻译按钮获取中文摘要

Plant domestication and the development of agriculture began shortly after 10,000 years ago in the Americas and several other primary centres around the world, and was one of humankind's most pivotal achievements. Recent advances in palaeobotany and molecular genetics have opened new avenues for understanding when, where, how, and why this crucial change first came about. For example, phylogenetic and phylogeographic studies of extant populations can often identify the wild ancestral population and thus the geographic cradle of origin for each domesticate, pointing the archaeologists to a limited area for survey and excavation. A growing body of genetic, biogeographical, and archaeobotanical data has now established Amazonia as one of the most important centres of plant domestication in the world. Recent genetic and biogeographic studies show that the transitional fringe of seasonal forests and savannahs in SW Amazonia, which encompass the upper Madeira River Basin, were probably the cradle of the domestication of several major American crops, including manioc (Manihot esculenta), peanuts (Arachis hypogaea), peach palm (Bactris gasipaes), coca (Erythroxylum coca), chilli peppers (Capsicum baccattum), annatto (Bixa orellana), and tobacco (Nicotina tabacco) (Clement et al. 2010; Piperno and Pearsall 1998). Despite being the most important centre of domestication in lowland South America, until now no interdisciplinary projects have documented the domestication of these important crops in their cradle of origin. To address this issue, we proposed to organise two workshops and conduct preliminary research activities to plan, write and submit a 3-5 yr international interdisciplinary project integrating molecular genetics, plant biogeography, archaeology, archaeobotany and paleoecology. The main objectives of the project will be to: i) investigate the history of major Amazonian crops including manioc, peach palm, chilli peppers and annatto; ii) reconstruct the context of early agriculture; and iii) investigate the timing and nature of human impact on the environment in the upper Madeira River, SW Amazonia. These objectives build on two previously separate lines of research coordinated by Iriarte and Clement: paleoecology and archaebotany of landscape transformations of the Araucaria forests of southern Brazil (AHRC-Fapesp) and the Purus-Madeira interfluve (ERC), and the origin, dispersal and phylogeography of native Amazonian crops (Fapeam, Fapeam-AIRD, CNPq, Fapesp), respectively.The project is well-timed to combine state-of-the-art techniques to address the complexity of plant domestication and the development of agriculture. Research on crop origins are benefiting from the refinement of microfossil botanical techniques, in particular starch granules retrieved from the residues of stone tools used to process plants, which are allowing archaeobotanists to document root crops in tropical regions exhibiting poor preservation of macrobotanical remains (visible remains of seeds and fruits) (Piperno 2011). Palaeoecological techniques will help reconstruct the Late Pleistocene through Holocene vegetation history of the upper Madeira River and, in particular, the natural environment and plant associations in which the first crops were domesticated. Particular emphasis will be given to how and when humans began to alter their environments, using fire history to reconstruct the relation between natural- and human-caused processes. Genetic analysis can identify the wild populations from which the first selections were derived to start the domestication of our modern crops, as well as to trace dispersals out of these centres of domestication.