Here's a sobering look at the human race's impact on its environment, from the authors of Origins (1977) and Origins Reconsidered (1992). In addition to his work in unearthing the remains of early hominids, Leakey spent five years as director of Kenya's Wildlife Services, fighting the spread of elephant poaching. Many of his insights in this book arise from the recognition that our species now has the power to bring about the extinction of a majority of our fellow inhabitants of the planet. Of course, mass extinctions are not rare in the fossil record; there have been at least five occasions when nearly two-thirds of living species disappeared from the face of the earth. Most were killed off by natural disasters, whether on the scale of the meteor impact believed to have ended the age of dinosaurs or an isolated habitat being destroyed by a change in local climate. But beginning with the late Pleistocene, the impact of human beings becomes evident. The extinction of large mammals--including mammoths, mastodons, giant ground sloths--in North America just over 10,000 years ago was almost certainly due to hunting by the newly arrived ancestors of today's Native Americans. Now the encroachment of human activities on the tropical rain forests (where a vast majority of living species reside) threatens to escalate the death toll to a level comparable to the five great prehistoric extinctions. The authors urge us to take action to prevent this catastrophe and present strong evidence that we are far richer leaving the forests undeveloped than we can ever be by letting them fall prey to monoculture and corporate use. Eloquently argued and rigorously supported by scientific evidence, this is a powerful document in the fight to preserve our natural heritage while there is still time.