To the philosophical the earth is eternal, while the human race -- presumptive keeper of the world's history -- is a mere speck in the rich stream of life. It is known that nothing upon Earth is forever; geography, climate, and plant and animal life are all subject to radical change. On five occasions in the past, catastrophic natural events have caused mass extinctions on Earth. But today humans stand alone, in dubious distinction, among Earth's species: Homo Sapiens possesses the ability to destroy entire species at will, to trigger the sixth extinction in the history of life. In The Sixth Extinction, Richard Leakey and Roger Lewin consider how the grand sprawl of human life is inexorably wreaking havoc around the world. The authors of Origins and Origins Reconsidered, unimpeachable authorities on the human fossil record, turn their attention to the most uncharted anthropological territory of all: the future, and man's role in defining it. According to Leakey and Lewin, man and his surrounding species are end products of history and chance. Now, however, humans have the unique opportunity to recognize their influence on the global ecosystem, and consciously steer the outcome in order to avoid triggering an unimaginable upheaval.