Abstract

Vegetation and climate influence the lifestyles and behaviour of the fauna in any region, so much so that animals with certain requirements can only live in suitable areas. Modern humankind can manipulate the vegetation to suit his needs but early humankind was at the mercy of the elements. Before we can postulate how and when evolutionary changes, modifications or adaptations occurred in the hominids, we need to know what the vegetation and climate were like. Comparative studies of fossil faunas with modern faunal distributions have been used to predict the palaeoclimate and vegetation. Pollen, phytolith and light isotope studies are also used, but the most direct method is to look at the actual fossil plants. Unfortunately these are not often preserved with the faunal remains but where they do occur an interesting picture emerges. Four case studies will be presented here, from East and South Africa, from short periods within a long time range. From Laetoli (Tanzania) fossil woods have been collected, between 4,3 and 3,8 Ma (million years), which show a complex diversity of species. Many seeds have been preserved just below the Foot Print Tuff, dated at 3,56 Ma. Detailed research has just begun on these plant remains. A multi-disciplinary project at Olduvai Gorge, Tanzania, has revealed many fossil plants: wood of Guibourtia coleosperma, sedges, grasses and other woody plants still to be identified. These plants come from upper Bed I and lower Bed II, approximately 1,8–1,7 Ma. Together with the tephrostratigraphy and sedimentology, these show that there have been dramatic and frequent fluctuations in the vegetation and climate. The saline lake has expanded and contracted, and faulting has also changed the drainage pattern, so the fluvial systems and wetlands have shifted a number of times. Fossil woods from the Sterkfontein Cave site in South Africa show that there was gallery forest during Member 4 times. One piece of wood has survived from the Florisbad site in South Africa. This is much younger, 259–125 Ka (thousand years), and appears to have been worked into a tool. The wood, Zanthoxylum chalybeum, is not a local one, and shows that there has been a climatic shift and the area is much drier today. The data and interpretation by other researchers and from other sites are discussed here.