Evolution's Rainbow. Joan Roughgarden

Чтение книги онлайн.

СКАЧАТЬ students to prepare them better to understand natural diversity. I propose new institutional processes to prevent continuing medical abuse of human diversity under the guise of treating diseases. I demand that genetic engineers take an oath of professional responsibility and that they be licensed to practice genetic engineering only after having passed a certifying examination. Finally, I float the idea that our country should construct a large statue and plaza, called the Statue of Diversity, which would be to the West Coast what the Statue of Liberty is to the East Coast.

      This book is my first “trade book,” a term publishers use for books intended for a wide audience rather than specifically for classroom use—my previous books have been specialized textbooks, monographs, or symposium proceedings.⁴ In this type of book I’m free to express opinion and to adopt an informal style. In this book, I freely declare where I’m coming from. Being up front about my position automatically raises the question of objectivity; I’ve told the truth, and the whole truth, as best I can. Yet I offer my own interpretation of the facts, as if I were a lawyer for the defense opposing lawyers for the “persecution.” You, my readers, are a jury of friends and neighbors, and you will make up your own mind. Please consider that everyone writing on these topics is writing from a particular perspective and with a vested interest. Some benefit from the biological excuse for male philandering that Darwin’s sexual selection theory provides. Others find validation in Darwin’s reinforcement of their aggressive worldview. Still others enjoy the genetic elitism of sexual selection theory, confident that their own genes are superior. I find that refuting sexual selection theory imbues female choice with responsibility for decisions about power and family far more sophisticated than what Darwin envisioned, and empowers varied expressions of gender and sexuality.

      At times I’ve loved writing this book; at other times I’ve felt afraid of what I have to say. The view of our bodies, of gender and sexuality, that emerges is strikingly new. But I’ve carried on because I’ve found the message to be positive and liberating. I hope you enjoy this book. I hope it betters your life.

      I thank the staff of the Falconer Biology Library at Stanford University for extensive help with research. I am deeply grateful for reviews from Blake Edgar, Patricia Gowaty, Scott Norton, Robert Sapolsky, and Bonnie Spanier, together with editorial improvements from the staff of the University of California Press, especially Elizabeth Berg and Sue Heinemann. I’ve been blessed by love from my closest friend, Trudy, and my sisters at Trinity Episcopal Church in Santa Barbara, especially Terry.

      PART ONE

      ANIMAL RAINBOWS

      1

      Sex and Diversity

      All species have genetic diversity—their biological rainbow. No exceptions. Biological rainbows are universal and eternal. Yet biological rainbows have posed difficulties for biologists since the beginnings of evolutionary theory. The founder of evolutionary biology, Charles Darwin, details his own struggle to come to terms with natural variation in his diaries from The Voyage of the Beagle.¹

      In the mid 1800s, living species were thought to be the biological equivalent of chemical species, such as water or salt. Water is the same everywhere. Countries don’t each have water with a unique color and boiling temperature. For biological species, though, often each country does have a unique variant. Darwin saw that finches change in body size from island to island in the Galápagos. We can see that robins in California are squat compared to robins in New England, and lizards of western Puerto Rico are gray compared to the brownish ones near San Juan. Darwin recognized that the defining properties of biological species, unlike physical species, aren’t the same everywhere. This realization, new and perplexing in the mid 1800s, remains at times perplexing today.

      In Darwin’s time, the Linnaean classification system, which is based on phyla, genera, species, and so forth, was just becoming established. Naturalists mounted expeditions to foreign places, collecting specimens for museums and then pigeonholing them into Linnaeus’s classification system. At the same time, physicists were developing a periodic table for elements—their classification scheme for physical species—and chemists were classifying recipes for various compounds on the basis of chemical bonds. But the biological counterpart of physical classification didn’t work very well. If Boston’s robin is different San Francisco’s, and if intermediates live at each gas station along Route 80, what do we classify? Who is the “true” robin? What does “robin” mean? Biological names remain problematic in zoology and botany today. Biological rainbows interfere with any attempt to stuff living beings into neat categories. Biology doesn’t have a periodic table for its species. Organisms flow across the bounds of any category we construct. In biology, nature abhors a category.

      Still, a robin is obviously different from a blue jay. Without names, how can we say whether it is a robin or a blue jay at the bird feeder? The work-around is to collect enough specimens to span the full range of colors in the species’ rainbow. Then specialists in biological classification, taxonomists, can say something like, “A robin is any bird between six and seven inches in length with a red to orange breast.”² No single robin models the “true robin” all robins are true robins. Every robin has first-class status as a robin. No robin is privileged over others as the exemplar of the species.

      DIVERSITY-GOOD OR BAD?

      Rainbows subvert the human goal of classifying nature. Even worse, variability in a species might signify something wrong, a screwup. In chemistry a variation means impurity, a flaw in the diamond. Doesn’t variability within a species also indicate impurity and imperfection? The most basic question faced by evolutionary biology is whether variation within a species is good in its own right or whether it is simply a collection of impurities every species is stuck with. Evolutionary biologists are divided on this issue.

      Many evolutionary biologists are positive about the rainbow. They view it as a reservoir of genes that can come to the forefront at different times and places to guarantee a species’ survival under changing conditions. The rainbow represents the species’ genetic assets.³ According to this view, the rainbow is decidedly good. This view is optimistic about the capability of species to respond to ever-changing environmental conditions. This view affirms diversity.

      Other evolutionary biologists are negative about the rainbow, believing that all gene pools—even our own—are loaded with deleterious mutations, or bad genes. During the 1950s, studies claimed that every person has three to five lethal recessive genes that would surface if they chose the wrong marriage partner, causing their children to die.⁴ This view is pessimistic about the future, suggesting that evolution has already reached its pinnacle and all variation is useless or harmful.⁵ This school of evolutionists believed in a genetic elite, advocating artificial insemination from sperm banks stocked with genes from great men. This view represses diversity.

      Darwin himself was ambivalent on the value of rainbows. Darwin argued that natural selection is the mechanism that causes species to evolve. On the one hand, because natural selection depends on variation, Darwin viewed the rainbow as a spectrum of possibilities constituting the species’ future. A species without variability has no evolutionary potential, like a firm with no new products in the pipeline. On the other hand, Darwin viewed females as shopping around for mates with desirable genes while rejecting those with inferior genes. This view demeans the variation among males and implies a hierarchy of quality, suggesting that female choice is about finding the best male rather than the best match. Darwin both affirmed and repressed diversity at different times within his career.

      The philosophical conflict over whether to affirm or to repress diversity is still with us today, permeating everything from the way biologists interpret motives for an animal’s choice of a particular mate to how medical doctors handle newborn babies in the hospital.

      THE COSTS VERSUS THE BENEFITS OF SEX

      How, СКАЧАТЬ