0684864533 Lee Alan Dugatkin the Imitation Factor: Evolution
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0684864533 Lee Alan Dugatkin The Imitation Factor: Evolution Beyond the Gene An acclaimed biologist, Dugatkin has identified and mapped the effects of a powerful, overlooked, and deceptively simple factor in evolutionary history. He shows how the imitation of one individual by another, in any species, is an essential and fundamental natural force that has enabled the growth of animal and human societies. Copyright c 2000 by Lee Alan Dugatkin To my mother, Marilyn, who's a real peach Preface WE DESPERATELY WANT TO THINK OF OURSELVES as somehow distinct from other life forms on our planet. We used to claim that we humans were unique in that we were the only species to make tools; now most of us have seen the nature programs on television featuring hammer-wielding monkeys and realize that this claim simply isn't true. Currently there is the sense that we are unique because "culture" is found only in humans. So where did culture come from? As we shall see, culture is not humanity's gift to the universe. It was invented long before we Homo sapiens arrived, and its power is evident in everything ranging from fish to nonhuman primates, and in virtually every behavioral context imaginable. It is not our gift, but it is our duty to understand it, to look into the heart of our social existence as individuals just as we have looked into the heart of our genetic existence as strands of DNA. We have learned that the replication of DNA is a fundamental principle of the continuation of life on earth. But we have not recognized the fundamental importance of another natural copying mechanism: the individual. Although individuals are not replicators in the traditional sense, the fact that we are veritable copy machines in the wild is the key to understanding the development of human culture and to understanding an unrecognized pervasive force of nature: the imitation factor. As is typical of any book that attempts to provide some kind of answer to a particularly large question, I am grateful for my interactions with hundreds of colleagues over the years and sincerely appreciate their work, thoughts, and encouragement. I thank my editor at The Free Press, Stephen Morrow, for all his help. Stephen has been critical in shaping this book at every stage along the way, and I consider myself very lucky to have had him as my editor on this project. Were it not for the advice and encouragement of my literary agent, Susan Rabiner, this work would never have come to be. Susan went through dozens of versions of early proposals for this book and was invaluable in helping me to see the forest through the trees. My wife, Dana, has read every word in this book more times than anyone ever should. Dana is more than a proofreader, though. Her thoughts along the way have made this book much more accessible to a broad audience. In every way, she is an incredible helpmate. My five-year-old boy, Aaron, also proofread parts of this book (honest), but it is the sparkle in his eyes that I'm really Page 1 0684864533 grateful for. Last, as always, I thank Dr. Jerram L. Brown for having confidence in my abilities early on. Fourteen years ago, Jerry believed in my talents, when in all honesty, there really was no reason to do so. The Cultured Animal Imitation is natural to man from childhood, one of his advantages over the lower animals being this, that he is the most imitative creature in the world and learns at first by imitation. --Aristotle ARISTOTLE RAISED ALL THE BEST QUESTIONS scientists are raising in laboratories today. That might be an overstatement, but if it is, it isn't a grand overstatement; it holds true for the basic questions that we address in my lab, as well as in the labs of many of my colleagues. But Aristotle was wrong, at least for the most part, about the ability of nonhuman animals to imitate. It was a big oversight. Nearly two and a half thousand years later, we discovered nature's blueprints-genes-but still remained almost blind to nature's way of transmitting information across the generations outside the genome. We tend to think we are the only animals able to do the trick of passing down the wisdom of our forebears. That trick is known as culture. Surprisingly, even guppies can do it. Looking at infants and children, you can see that Aristotle is correct that humans learn first by imitation. A vast amount of preschool education comes from mimicking the behavior of others, usually parents. This is so obvious it can be scary. Looking at your child gives something of a mirror image of your own actions-and that isn't always a pleasant experience. No one doubts the importance of imitation in humans. But Aristotle did not really recognize imitation as the root of cultural transmission, nor did he see that many animals, not only ourselves, have been able to transmit culture in just this way. Indeed, no one at all has recognized this until very recently. But it is now a scientific fact that illuminates the mysterious origin of culture itself-and how evolution proceeds beyond the gene. GUPPY CULTURE I spend a lot of time watching guppies. To be honest, I spend more time with guppies than any sane person should, unless that person happens to be a behavioral ecologist- someone who studies the evolution of social behavior-and even then it is a close call. Watch guppies long enough, and you see that sex is what life in a guppy neighborhood (be it a tank or stream) revolves around. Males want to mate with any willing female, and spend a great deal of their time pursuing this desire. Females, on the other hand, spend the majority of their time avoiding the constant sexual harassment to which they are subjected. What determines who mates with whom in guppy society is a fascinating concoction of genetic drives and imitation. Females have a genetic predisposition to mate with colorful males, but layered on top of this is is a strong inclination to imitate the choice of mates that other females make. Page 2 0684864533 All else being equal, female guppies mate with colorful males and in essence obey their genetic code. But, hold everything constant, and females also imitate each other's choice of mating partner-and that alone is a rather remarkable finding. Female guppies, with brains no bigger than a pinhead, copy each other's choice of mates. Yet the story of copying and mate choice hardly ends there. One can move on to ask how genes and culture interact to shape guppy mate choice. That is, if we consider copying and imitation (and teaching) to be forces underlying the cultural transmission of behavior, how do these forces interact with genes coding for behavior? We might think guppies alone should not prove the likes of Aristotle wrong. However, the role of culture in animal life has been observed in many many species, and its effects are clearly quite powerful. Various forms of culture influence mate choice in everything from bugs, fish, and birds to deer and primates, including, of course, humans. In many of these instances, culture and genetics interact in unexpected and bizarre ways. Furthermore, culture is in no way restricted to the subject of mate choice; it invades virtually every aspect of animal behavior. Culture, or more specifically cultural transmission of information through imitation, was a force long before humans came on the scene and continues to be an important factor in what many would consider to be very simple animals. And imitation is a unique factor because the actions of a few individuals, if copied, can have long-term evolutionary consequences at the population level. The quirky behavior of just a few individuals can live on across the generations and across thousands, potentially even millions, of years. That culture plays such a strong role in animal choice is a controversial claim and an even more consequential fact. Consider that cultural transmission of information can work with lightning speed (when compared with the timescale on which genetic change takes place). The action of even a single individual, if it is copied by many, can snowball through a population with evolutionary reverberation. Moreover, new theory in biology can predict when cultural or genetic factors will predominantly drive behavior. That we can now balance hereditary forces against cultural ones is an astonishing achievement of modern science. But we need to step back and define what culture really is and answer some related questions before we consider the larger implications of this work. Evolutionary biologists are generally in agreement that the process of natural selection is the primary (but not exclusive) agent driving evolutionary change. There are certainly some prominent critics of this view, but most biologists would not quibble with this statement, especially if one were talking about the evolution of social behavior. To understand virtually any aspect of life on earth or elsewhere, scientists will tell you, we must understand how the process of natural selection operates. NATURAL SELECTION AND GENES Given the monumental impact of his work in both the social and natural sciences, it is often surprising to learn that Charles Robert Darwin's ideas with respect to natural selection are Page 3 0684864533 remarkably straightforward. Consider any characteristic of an organism-height, weight, visual acuity, or anything else. If variations in this characteristic exist, such that, for example, there are differences in height among individuals in a population, and if there exists a means by which individuals of different height produce offspring that resemble themselves, then any variant that outreproduces others will spread through time.