Middle Miocene Grasslands of Kenya

这是一项研究土壤和草化石的建议，作为东非中新世中期草原的证据，以及它们在人类类人猿祖先进化中的作用。自查尔斯·达尔文时代以来，草原在人类进化中的作用一直存在争议，肯尼亚中新世中期（14 Ma）草原的存在一直存在争议。现在有几条证据线聚集在一起，表明肯尼亚中中新世草原：(1)化石土壤中的碳酸盐和哺乳动物牙齿中的磷灰石的同位素研究表明热带草地植被，(2)化石土壤与现代草地（Mollisols）相似，(3)羚羊化石上的放牧口和牙齿划痕，(4)化石草具有丰富的猫白石（植岩）和稀少的孔（气孔）。这些发现在某些情况下只是基于初步研究，现在需要扩展到分布在肯尼亚西南部的中新世中期（13-16 Ma）的更多遗址：Ombo， Majiwa, Maboko, Nyakach, Fort Ternan， Serek和Kapsibor。每个地点的土壤化石将被描述并取样供实验室分析。草化石也将被收集起来，并送回实验室进行显微镜检查，以便通过计算机数据库识别它们。还计划进行禾草和土壤化石的同位素研究，以确定禾草和植被的种类（C3或C4禾草）。该项目建立在先前一个成功项目的基础上，该项目提供了对最早的东非草原的生理、自然、植物组成和范围的详细视图。

This is a proposal to study fossil soils and grasses as evidence for Middle Miocene grasslands in East Africa and their role in the evolution of apelike ancestors of humans. The role of grasslands in human evolution has been debated since Charles Darwin's day, and the existence of Middle Miocene (14 Ma) grasslands in Kenya has continued to be controversial. Several lines of evidence now converge to indicate Middle Miocene grasslands in Kenya: (1) isotopic study of carbonate in fossil soils and apatite of mammalian teeth indicating tropical grassy vegetation, (2) fossil soils similar to those of modern grasslands (Mollisols), (3) grazing muzzle and tooth scratching on antelope fossils, and (4) fossil grasses with the abundant opal (phytoliths) and scarce pores (stomates) of open country grasses. These findings are in some cases based on only preliminary studies and now need to be extended to more sites of Middle Miocene age (13-16 Ma) scattered through southwestern Kenya: Ombo, Majiwa, Maboko, Nyakach, Fort Ternan, Serek and Kapsibor. Fossil soils at each site will be described and sampled for laboratory analysis. Fossil grasses will also be collected and returned to the laboratory for the microscopic examination needed to identify them using a computer database. Also planned are isotopic studies of the grasses and fossil soils to determine the kinds of grasses and vegetation present (C3 or C4 grasses). This project builds on the highlights of a previously successful program to provide a detailed view of the physiology, nature, botanical composition and extent of the earliest East African grasslands.