Agriculture, Paleoenvironment, and Human Occupation in the Pacific Coastal Lowlands of Southern Mesoamerica

在国家科学基金会的支持下，赫克托·内夫博士和他的合作者将完成对危地马拉太平洋沿岸五个沉积物岩心的分析，这些岩心已知跨越了人们最初开始为农业和其他谋生目的而改变地形的时间段。来自一个地点的初步结果表明，在公元前5000年之前，人们将玉米或玉米的直系祖先带到了该地区，大约在公元前3500年左右开始发生了戏剧性的农业集约化。通过植物微化石(植硅体和花粉)和木炭频率的变化以及沉积速率的变化，可以在沉积物岩心中检测到人类改造和其他景观变化的信号。当人们砍伐或烧毁热带森林用于农业时，随着树木和其他森林物种的减少，杂草和木炭在记录中变得更加常见。随着森林覆盖的消失，沉积速率也往往会增加。玉米和其他农作物可以从花粉和植硅体中识别出来，这两种证据的结合提供了最可靠的识别(植硅体是积累不断生长的植物的微小硅体)。这些变化是通过AMS放射性碳测年从岩心中选定的水平对有机质进行年代测定的。危地马拉太平洋沿岸公元前3500年至公元前800年之间的时期特别令人感兴趣，因为正是在这一时期，中美洲复杂社会的许多独特特征汇聚在一起。到那个时期结束时，大多数地区的人们严重依赖玉米农业，正在建造具有纪念性建筑和精致石雕的大型遗址，社会分层已经出现。生计的根本性转变、人们越来越多地被束缚在特定地点，以及开始对建筑基础设施进行重大投资，构成了中美洲文明的出现。不幸的是，这一太平洋地区的研究相对较少，与墨西哥湾沿岸的奥尔梅克中心地带相比，人们对这一序列的细节知之甚少。内夫博士和他的同事的工作将为这一文化进步建立一个环境背景，并为这一过程本身提供洞察力。

With National Science Foundation support Dr. Hector Neff and his collaborators will complete the analysis of five sediment cores from Pacific coastal Guatemala that are known to span the time periods when people first began modifying the landscape for agriculture and other subsistence purposes. Preliminary results from one location suggest that people brought maize or a direct ancestor of maize to the region before 5000 B.C. and that dramatic agricultural intensification took place beginning around 3500 B.C. The signal of human modification and other landscape changes can be detected in sediment cores via the changing frequencies of plant microfossils (phytoliths and pollen) and charcoal together with variation in sedimentation rates. When people cut or burn down the tropical forest for agriculture, weeds and charcoal become more common in the record as trees and other forest species decline. Sedimentation rates also tend to increase as forest cover is removed. Maize and other agricultural crops can be identified both from pollen and phytoliths, the combined evidence providing the most secure identification (phytoliths are microscopic silica bodies that accumulate growing plants). These changes are placed in a chronological context by AMS radiocarbon dating of organic matter from selected levels in the cores. The period between 3500 B.C. and 800 B.C. in Pacific coastal Guatemala is of particular interest because it was during this period that many of the distinctive characteristics of Mesoamerican complex societies coalesced. By the end of the period, people in most locations depended heavily on maize agriculture, large sites with monumental architecture and elaborate stone sculpture were being constructed, and social stratification had appeared. The fundamental shifts in subsistence, the increased tethering of people to specific locations, and the beginning of major investment in architectural infrastructure constituted the emergence of Mesoamerican civilization. Unfortunately this Pacific region has been relatively understudied and details of the sequence are poorly known compared, for example, to the Olmec heartland on the Gulf Coast of Mexico. The work of Dr. Neff and his colleagues will both establish an environmental context for this cultural progression and provide insight into the process itself.