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Mysteries of the Organism

HUMAN NATURES Genes, Cultures, and the Human Prospect By Paul R. Ehrlich; Island Press / Shearwater Books: 500 pp., $29.95

October 22, 2000|IAN TATTERSALL | Ian Tattersall is the author, most recently, of "Becoming Human" and "Extinct Humans" (with Jeffrey Schwartz). He is a curator at the American Museum of Natural History in New York City

Why are people so appalling? Why are people so admirable? Why are people as a whole--or even as individuals--so difficult to pin down? Why, indeed, are people so relentlessly driven to ask "Why?" Questions such as these, particularly in combination, cut close to the heart of what it means to be human, and "Human Natures" is an earnest attempt by the distinguished Stanford biologist Paul R. Ehrlich to provide an answer to the timeless conundrum that our strange species poses.

Ehrlich is broadly read and well-informed. His discussion ranges easily from the role of disease in human history to differences in perception of the world among different cultures and beyond, and what his book amounts to is the ruminations of an intelligent, sensitive and thoughtful biologist on a host of problems and considerations pertinent--in a variety of ways--to humanity's relationship, past and present, with the rest of the living world. It is a protracted, quirky and, in places, brilliant consideration of a remarkable range of topics that every concerned individual should be aware of. And despite a sometimes rather forbidding academic apparatus, it makes an enjoyable and frequently engrossing read.

Ehrlich discusses, for instance, why human females have concealed ovulation, how agriculture evolved and what the Easter Islanders did to transform it from a forested paradise to a wasteland capable of supporting only a small and deprived population that was a shadow of its former self. He considers humanity's place in nature: What we are doing to the world around us, whether it is possible for us to derive any ethical principles from the contemplation of the world beyond ourselves and, most important, what the prospects are for creating a "conscious evolutionary process" that will change our emphasis from simply "doing" to asking why.

At the beginning of "Human Natures" Ehrlich writes that this volume is in response to those reductionists who believe that all of our bizarre behaviors can be reduced to the influence of genes acquired many millenniums ago in our ancestral hunting-gathering "environment of evolutionary adaptedness." The first dozen pages or so contain the most concise and sensible summary I've seen anywhere of how genes, the factors of heredity, make individuals both alike and different. Indeed, in certain ways they make the remaining 400-odd remorselessly footnoted pages seem almost superfluous. (By the way, don't refer to the 2,000-odd endnotes as you read the book, for you'd quickly lose track of the bigger picture. But don't forget to browse through them--rather as you might an encyclopedia. Like the rest of the volume, these notes are a feast of odd observations, and are a large part of the fun of the whole thing.)

By the end of the book, however, it becomes hard to detect exactly where Ehrlich's sympathies lie on the matter of "evolutionary psychology," perhaps because his view of the evolutionary process itself is in some ways identical to that of the evolutionary psychologists. But his ambitions extend much further than the question of genes versus environment in determining how individual organisms turn out. Notably, in the case of our own species, he wants to broaden notions of biological evolution to embrace "cultural evolution." His belief is that a better understanding of evolution, and in particular natural selection, will help us deal with the host of rapidly intensifying problems that face humankind. Readers of Ehrlich's other works will not be surprised to learn that the problems that particularly worry him lie in the arena of our relationship with the environment that continues, if with increasing reluctance, to support us.

Close to a century and a half ago, Charles Darwin proposed that species of organisms should be expected to show slow change over time. Noting that individuals invariably differ in inherited ways and that in every generation far more offspring are typically born than will survive to reproduce themselves, Darwin argued that those most favored by nature--those "best adapted"--will leave a disproportionately large number of offspring. With the passage of generations, the advantageous adaptations of the favored individuals should thus become more common in their populations at the expense of less advantageous characteristics. "Natural selection" is simply Darwin's term for any and all factors that affect this process of differential reproduction and that cause slow change over the generations.

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