SPECIATION, EXTINCTION AND CLIMATIC-CHANGE IN HOMINID EVOLUTION

The temporal association of hominid evolution with a period of global climatic instability and cooling is suggestive of a causal relationship. A number of authors have proposed a climatic forcing model for the timing and nature of evolutionary changes in human evolution during the Pliocene and Pleistocene (5-3 Mya), such as the appearance of new taxa, and by inference only a limited role for continuous evolutionary change in response to inter- and intra-specific competition at the local level. A major problem with such models is that both climatic change and hominid evolution are now recognised as complex with numerous events. By splitting climatic change as revealed in deep sea cores into a number of distinct attributes (temperature, stability and variability) and examining the relationship of each to the appearance, diversity and disappearance of hominid taxa it is possible to investigate more closely the effect of climatic change on hominid evolution. It is shown that the effect of climatic change can be observed in relation to extinction events, but that there is no significant relationship with the first appearance of hominid taxa. This implies that the mechanism by which climate influences evolution is primarily through extinction, and that further factors dependent upon local competitive conditions play a significant part in the appearance of new taxa. © 1994 Academic Press. All rights reserved.