LIFE'S HISTORY WITH THE EARTH

Modern advances in the earth sciences have at last provided us with a good understanding of how our planet 'works.' Biologists are now able to discern how the evolutionary history of life has been affected by planetary events and how, in turn, life has affected Earth's development. We can identify the conditions under which life emerged and the eventual evolution of complex organisms which now live alongside prokaryote organisms which may have changed little over billions of years since their origins. The rich biodiversity existing today can be seen as the end point of evolutionary processes which have seen plate tectonics, volcanism and impacts all play a part in determining the pattern of casualties and survivors over time. They have all affected the outcomes of natural selection. Despite repeated bottlenecks during which conditions have been so severe as to cause mass extinctions, selection has been able to generate adaptive radiation amongst the survivors. The current mass extinction, human induced, is unlikely to offer such opportunities unless we can rapidly achieve a better balance with natural systems.