In Human Natures, Paul Ehrlich—professor of biology at Stanford University and lifelong champion of ecological causes—examines the overwhelming burden on our natural resource supply demanded by Western culture. Our consumption-oriented development, he argues, can be traced back to the belief systems that engendered the industrial revolution in Western Europe--the belief that unrestrained capitalism is necessary to sustain economic growth.

The underlying theme of Ehrlich’s book is best summarized in an early passage: “We know why biodiversity is disappearing—the primary reason is that Homo sapiens is destroying natural habitats, and our capability of so doing, as we'll see, is largely due to our cultural evolution. Knowing how a vast array of species, including our own, evolved and how these species shaped one another and their environments may help us to stanch the flow of extinction and even to regenerate some of our lost biological heritage. The process of diversification has occurred over billions of years, and an understanding of it is integral to our understanding the generation of our modern human natures. Many aspects of our natures evolved both biologically and culturally to deal with elements of the diversity that surrounds us and with which we have long interacted as food, predators, parasites, shelter, and so on” (45). Among the many causes for the declining habitability of the earth, Ehrlich cites suppression of international birth control, intensification of agricultural production, unsustainable harvesting of sea-life, and the flagrant activities of multi-national corporations.

He uses the intensive production of asparagus in Peru as a case study to point towards impending catastrophe through soil erosion. Forced yields of three crops per year will almost certainly lead to non-recoverable depletion of nutrients as well as salinization of the soil. The ultimate impact—irrevocable destruction of land and species—has been seen in countless prior agricultural failures around the world. But Ehrlich sees something bigger than localized tragedy. We already possess knowledge of historic events which caused the decline and ultimate failures of city-states such as those in Greece, Easter Island and historic Nineveh and Babylon in Iraq, Ehrlich argues. Strong evidence points towards aggressive de-forestation as the cause of soil erosion and change in the climate which lead to the aridity of the land in these cases. Are we failing to read our own history?

With his insight and background of extensive research in the field of ecology, Ehrlich is able to present a well rounded, comprehensive view of the devastating ecological problems that we face today. The book is recommend for anyone concerned about the declining habitability of our earth and who shares Ehrlich’s interest in the overpopulation of earth; degradation of the atmosphere, soil and water; and the loss of biodiversity.