Late Pleistocene European and Late Miocene African accelerations of faunal change in relation to the climate and as a background to human evolution

摘要

Faunal change can be described in terms of faunal turnover rates and average species longevity (=species duration, species lifespan). However, the plain faunal turnover rate is related to species richness, and therefore a faunal turnover index (100 × faunal turnover rate/species richness) is used. The changes in these values are studied for large mammals of the past 24 My of Western Europe and past 20 My of Africa. In Africa and in Western Europe, discrete events of acceleration of the rate of faunal change occurred at different moments and as responses to different climatic events. In Africa, an abrupt decrease in average species longevity and a very moderate increase in the index of faunal turnover occurred around 7.5 M.A., followed by a spectacular increase in species richness (and plain faunal turnover rates). These events are probably related to the increasing abundance of C_4 grasses. In Europe an overall trend in decreasing average species longevity set in after 9 Ma, accelerated around 2.5 and reached very low values around 0.01 Ma, while plain faunal turnover rates and the faunal turnover index increased from 1.2 Ma onward and reached extreme values during the later Pleistocene. These changes are probably related to the overall cooling trend and the increasing importance of the Milankovich cycles of obliquity around 2.6 Ma and eccentricity around 1.2-0.9 Ma. The acceleration in faunal change in Africa is more or less coincident with the first fossil record indicating bipedalism in hominoids. The first human dispersal into Europe occurred against a background of accelerating faunal change. The later Pleistocene to Holocene is a period of intense faunal change. Neanderthals lived and evolved in this changing environment until their replacement by our own species.