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Why do we behave the way we do? Biologist Paul Ehrlich suggests that although people share a common genetic code, these genes "do not shout commands at us...at the very most, they whisper suggestions." He argues that human nature is not so much result of genetic coding; rather, it is heavily influenced by cultural conditioning and environmental factors. With personal anecdotes, a well-written narrative, and clear examples, Human Natures is a major work of synthesis and scholarship as well as a valuable primer on ...
Why do we behave the way we do? Biologist Paul Ehrlich suggests that although people share a common genetic code, these genes "do not shout commands at us...at the very most, they whisper suggestions." He argues that human nature is not so much result of genetic coding; rather, it is heavily influenced by cultural conditioning and environmental factors. With personal anecdotes, a well-written narrative, and clear examples, Human Natures is a major work of synthesis and scholarship as well as a valuable primer on genetics and evolution that makes complex scientific concepts accessible to lay readers.
Evolution And Us
"Among scientific theories, the theory of evolution has a special status, not only because some of its aspects are difficult to test directly and remain open to several interpretations, but also because it provides an account of the history and present state of the living world."
"... when we regard every production of nature as one which has had a history; when we contemplate every complex structure and instinct as the summing up of many contrivances, each useful to the possessor ... how far more interesting, I speak from experience, will the study of natural history become!"
Columbine High School, Littleton, Colorado, April 20, 1999. Two young men approached their schoolmates and whipped semi-automatic weapons from under their black trench coats. The slaughter began. According to some accounts, one student was asked whether she believed in God. When shereplied, "Yes," she was shot dead. An athlete was gunned down because he was black. All told, thirteen people, most of them students, were killed and twenty-three were wounded before the two gunmen killed themselves. This was only one of a dozen or so incidents of senseless mass shootings within a year in the United States. Why did it happen? Why do some kids behave so differently from others? Did the two gunmen have abusive parents? Were they cursed with "killer genes"? Had television, movie, and video game violence warped their minds?
Such carnage is not a special product of human natures in the United States. Similar murder sprees occur around the world. In 1996 in Dunblane, Scotland, a "peculiar" man used four handguns to slaughter sixteen kindergarten students and their teacher. Shortly thereafter at Port Arthur, Tasmania, a gunman killed thirty-five innocent people, ranging in age from three to seventy-two. Many people also seem ready and willing to participate in much vaster, more organized schemes of murder--to commit genocide, be it in Nazi Germany or Rwanda. And clean-cut American boys, flying bombers, incinerated hundreds of thousands of Japanese and German men, women, and children in World War II. Why do people do such things? Is it human nature? Do we share with chimps a genetically programmed propensity for violence and simply have better weapons and organization than they do? But what, then, of the majority of human beings who don't do such things?
Of course, there is a brighter side to our natures. Many human beings risk their lives for others, and some die in the attempt to help. At the Yad Vashem Holocaust memorial outside Jerusalem, there is an "Avenue of the Righteous Among the Nations," along which more than 6,000 trees have been planted, each to memorialize a non-Jew who helped a Jew without expectation of reward. What moved those people and others like them to stand up to one of history's most horritic regimes? Why did they risk their lives to save individuals whom their neighbors were willing to see carted away to their doom? Expression of genes for altruism? Simple conviction, learned in childhood, that it was the right thing to do as one human being to another?
President Jimmy Carter was appalled at having had adulterous thoughts; Bill Clinton and Francois Mitterrand seem to have had fewer qualms. Is Clinton just a "product of his time," the sexually liberating 1960s, and are the French just innately different? Why do some men apparently seek more sexual variety than others?
Pedro, a middle school student from a family of poor Mexican immigrants, desperately wants to go to college even though no one in his family has ever done so. He studies hard, but his school counselor discourages him. Tests indicate that his intelligence quotient (IQ) is only 98. Grace, on the other hand, a student from a well-to-do Anglo family, scored 125 on the IQ test. She seems bound for Yale University, the college her father attended. She hardly studies at all, yet she gets terrific grades. Did Grace win out in the "smart gene" lottery by being born an Anglo, whereas Pedro had the bad luck to be born into the "wrong" ethnic group? Or is Pedro loaded with smart genes but deprived of an opportunity to develop his potential and held back by a meaningless score on a biased test?
As I write this, my back is aching. That's because I, like the rest of my species, stand on my "hind legs." Why isn't it our nature to run around on all fours like a proper mammal? Why do we end up with such weird posture--a posture that forced me to undergo back surgery and causes virtually all adult Homo sapiens to experience back pain?
Where did we get our capacity for conscious awareness and our ability to build long-term plans in our minds and then talk about those plans with other human beings? And with all that capacity for memory and foresight, why do I still eat rich chocolate desserts whenever I get the chance? I remember the articles I've read that tell me how bad saturated fat is for my circulatory system, and I can foresee a coronary in my future unless I'm careful (or lucky!). But still I have a lust for hot-fudge sundaes. A recent magazine headline suggests I'm far from alone: "Fifty Secrets to Fight Fat--No Dieting Required! Plus, Outsmart Your Family Fat Gene!" Why do so many of us have irresistible cravings, and different ones at that, including addictions to much more life-threatening substances than chocolate?
I had been struggling to learn Spanish for almost a decade, starting in my fifties, when my granddaughter Jessica entered a Spanish immersion school at the age of five. A few days after she started, I tried a little Spanish on her, asking her whether she wanted some chocolate. Her response was an immediate correction: "No, Grandpa, not chah-kah-lah-tay--it's choh-koh-lah-tay." Why are children natural linguists, whereas adults generally aren't? Why is it that only we human beings, of all creatures, talk, and write to one another?
How Can We Explain Human Behavior?
When we think about our behavior as individuals, "Why?" is a question almost always on the tips of our tongues. Sometimes that question is about perceived similarities: why is almost everyone religious; why do we all seem to crave love; why do most of us like to eat meat? But our differences often seem equally or more fascinating: why did Sally get married although her sister Sue did not, why did they win and we lose, why is their nation poor and ours rich? What were the fates of our childhood friends? What kinds of careers did they have; did they marry; how many children did they have? Our everyday lives are filled with why's about differences and similarities in behavior, often unspoken, but always there. Why did one of my closest colleagues drink himself to death, whereas I, who love wine much more than he did, am managing to keep my liver in pretty good shape? Why, of two very bright applicants admitted to our department at Stanford University for graduate work, does one turn out pedestrian science and another have a spectacular career doing innovative research? Why are our natures often so different, and why are they so frequently the same?
The background needed to begin to answer all these whys lies within the domain of human biological and cultural evolution, in the gradual alterations in genetic and cultural information possessed by humanity. It's easy to think that evolution is just a process that sometime in the distant past produced the physical characteristics of our species but is now pretty much a matter of purely academic, and local school board, interest. Yet evolution is a powerful, ongoing force that not only has shaped the attributes and behaviors shared by all human beings but also has given every single individual a different nature.
A study of evolution does much more than show how we are connected to our roots or explain why people rule Earth--it explains why it would be wise to limit our intake of beef Wellington, stop judging people by their skin color, concern ourselves about global warming, and reconsider giving our children antibiotics at the first sign of a sore throat. Evolution also provides a framework for answering some of the most interesting questions about ourselves and our behavior.
When someone mentions evolution and behavior in the same breath, most people think immediately of the power of genes, parts of spiral-shaped molecules of a chemical called DNA. Small wonder, considering the marvelous advances in molecular genetics in recent decades. New subdisciplines such as evolutionary medicine and evolutionary psychology have arisen as scientists have come to recognize the importance of evolution in explaining contemporary human beings, the network of life that supports us, and our possible fates. And the mass media have been loaded with stories about real or imagined links between every conceivable sort of behavior and our genes.
Biological evolution--evolution that causes changes in our genetic endowment--has unquestionably helped shape human natures, including human behaviors, in many ways. But numerous commentators expect our genetic endowment to accomplish feats of which it is incapable. People don't have enough genes to program all the behaviors some evolutionary psychologists, for example, believe that genes control. Human beings have something on the order of 100,000 genes, and human brains have more than 1 trillion nerve cells, with about 100-1,000 trillion connections (synapses) between them. That's at least 1 billion synapses per gene, even if each and every gene did nothing but control the production of synapses (and it doesn't). Given that ratio, it would be quite a trick for genes typically to control more than the most general aspects of human behavior. Statements such as "Understanding the genetic roots of personality will help you 'find yourself' and relate better to others" are, at today's level of knowledge, frankly nonsensical.
The notion that we are slaves to our genes is often combined with reliance on the idea that all problems can be solved by dissecting them into ever smaller components--the sort of reductionist approach that has been successful in much of science but is sometimes totally unscientific. It's like the idea that knowing the color of every microscopic dot that makes up a picture of your mother can explain why you love her. Scientific problems have to be approached at the appropriate level of organization if there is to be a hope of solving them.
That combination of assumptions--that genes are destiny at a micro level and that reductionism leads to full understanding--is now yielding distorted views of human behavior. People think that coded into our DNA are "instructions" that control the details of individual and group behavior: that genetics dominates, heredity makes us what we are, and what we are is changeable only over many generations as the genetic endowment of human populations evolves. Such assertions presume, as I've just suggested, that evolution has produced a level of genetic control of human behavior that is against virtually all available evidence. For instance, ground squirrels have evolved a form of "altruistic" behavior--they often give an alarm call to warn a relative of approaching danger. Evidence does indicate that this behavior is rooted in their genes; indeed, it probably evolved because relatives have more identical genes than do unrelated individuals. But some would trace the "altruistic" behavior of a business executive sending a check to an agency helping famine victims in Africa, or of a devout German Lutheran aiding Jews during the Holocaust, to a genetic tendency as well. In this view, we act either to help relatives or in the expectation of reciprocity--in either case promoting the replication of "our" genes. But experimental evidence indicates that not all human altruistic behavior is self-seeking--that human beings, unlike squirrels, are not hereditarily programmed only to be selfish.
Another false assumption of hereditary programming lies behind the belief that evolution has resulted in human groups of different quality. Many people still claim (or secretly believe), for example, that blacks are less intelligent than whites and women less "logical" than men, even though those claims are groundless. Belief in genetic determinism has even led some observers to suggest a return to the bad old days of eugenics, of manipulating evolution to produce ostensibly more skilled people. Advocating programs for the biological "improvement of humanity"--which in the past has meant encouraging the breeding of supposedly naturally superior individuals--takes us back at least to the days of Plato, more than two millennia ago, and it involves a grasp of genetics little more sophisticated than his.
Uniquely in our species, changes in culture have been fully as important in producing our natures as have changes in the hereditary information passed on by our ancestors. Culture is the nongenetic information (socially transmitted behaviors, beliefs, institutions, arts, and so on) shared and exchanged among us. Indeed, our evolution since the invention of agriculture, about 10,000 years ago, has been overwhelmingly cultural because, as we shall see, cultural evolution can be much more rapid than genetic evolution. There is an unhappy predilection, especially in the United States, not only to overrate the effect of genetic evolution on our current behavior but also to underrate that of cultural evolution. The power of culture to shape human activities can be seen immediately in the diversity of languages around the world. Although, clearly, the ability to speak languages is a result of a great deal of genetic evolution, the specific languages we speak are just as clearly products of cultural evolution. Furthermore, genetic evolution and cultural evolution are not independent. There are important "coevolutionary" interactions between them. To take just one example, our farming practices (an aspect of our culture) change our physical environment in ways that alter the evolution of our blood cells, as we shall see in the next chapter.
Not only is the evolution of our collective nongenetic information critical to creating our natures, but also the rate Of that evolution varies greatly among different aspects of human culture. That, in turn, has profound consequences for our behavior and our environments. A major contemporary human problem, for instance, is that the rate of cultural evolution in science and technology has been extraordinarily high in contrast with the snail's pace of change in the social attitudes and political institutions that might channel the uses of technology in more beneficial directions. No one knows exactly what sorts of societal effort might be required to substantially redress that imbalance in evolutionary rates, but it is clear to me that such an effort, if successful, could greatly brighten the human prospect.
Science has already given us pretty good clues about the reasons for the evolution of some aspects of our natures; many other aspects remain mysterious despite a small army of very bright people seeking reasons. Still other aspects (such as why I ordered duck in the restaurant last night rather than lamb) may remain unanswerable--for, as I will argue in a later chapter, human beings have a form of free will. But even to think reasonably about our natures and our prospects, some background in basic evolutionary theory is essential. If Grace is smarter than Pedro because of her genes, why did evolution provide her with "better" genes? If Pedro is actually smarter than Grace but has been incorrectly evaluated by an intelligence test designed for people of another culture, how did those cultural differences evolve? If I was able to choose the duck for dinner because I have free will, what exactly does that mean? How did I and other human beings evolve that capacity to make choices without being complete captives of our histories? Could I have exercised my free will to eat a cockroach curry had we been in a restaurant that served it (as some in Southeast Asia do)? Almost certainly not--the very idea nauseates me, probably because of an interaction between biological and cultural evolution.
Every attribute of every organism is, of course, the product of an interaction between its genetic endowment and its environment. Yes, the number of heads an individual human being possesses is specified in the genes and is the same in a vast diversity of environments. And the language or languages a child speaks (but not her capacity to acquire language) is determined by her environment. But without the appropriate internal environment in the mother's body for fetal development, there would be no head (or infant) at all; and without genetically programmed physical structures in the larynx and in the developing brain, there would be no capacity to acquire and speak language. Beyond enabling us to make such statements in certain cases, however, the relative contributions of heredity and environment to various human attributes are difficult to specify. They clearly vary from attribute to attribute. So although it is informative to state that human nature is the product of genes interacting with environments (both internal and external), we usually can say little with precision about the processes that lead to interesting behaviors in adult human beings. We can't partition the responsibility for aggression, altruism, or charisma between DNA and upbringing. In many such cases, trying to separate the contributions of nature and nurture to an attribute is rather like trying to separate the contributions of length and width to the area of a rectangle, which at first glance also seems easy. When you think about it carefully, though, it proves impossible.
Diverse notions of inherited superiority or inferiority and of characteristic innate group behaviors have long pervaded human societies: beliefs about me divine right of kings; "natural" attributes that made some people good material for slaves or slave masters; innate superiority of light-skinned people over dark-skinned people; genetic tendencies of Jews to be moneylenders, of Christians to be sexually inhibited, and of Asians to be more hardworking than Hispanics; and so on. Consider the following quote from a recent book titled Living with Our Genes, which indicates the tone even among many scientists: "The emerging science of molecular biology has made starting discoveries that show beyond a doubt that genes are the single most important factor that distinguishes one person from another. We come in large part ready-made from the factory. We accept that we look like our parents and other blood relatives; we have a harder time with the idea we act like them."
In fact, the failure of many people to recognize the fundamental error in such statements (and those in other articles and books based on genetic determinism, such as Richard J. Herrnstein and Charles Murray's famous The Bell Curve) is itself an environmental phenomenon--a product of the cultural milieu in which many of us have grown up. Genes do not shout commands to us about our behavior. At the very most, they whisper suggestions, and the nature of those whispers is shaped by our internal environments (those within and between our cells) during early development and later, and usually also by the external environments in which we mature and find ourselves as adults.
How do scientists know that we are not simply genetically programmed automata? First, biological evolution has produced what is arguably the most astonishingly adaptable device that has ever existed--the human nervous system. It's a system that can use one organ, the brain, to plan a marriage or a murder, command muscles to control the flight of a thrown rock or a space shuttle, detect the difference between a 1945 Mouton and a 1961 Latour, learn Swahili or Spanish, and interpret a pattern of colored light on a flat television screen as a three-dimensional world containing real people. It tries to do whatever task the environment seems to demand, and it usually succeeds--and because many of those demands are novel, there is no way that the brain could be preprogrammed to deal with them, even if there were genes enough to do the programming. It would be incomprehensible for evolution to program such a system with a vast number of inherited rules that would reduce its flexibility, constraining it so that it could not deal with novel environments. It would seem equally inexplicable if evolution made some subgroups of humanity less able than others to react appropriately to changing circumstances. Men and people with white skin have just as much need of being smart and flexible as do women and people with brown skin, and there is every reason to believe that evolution has made white-skinned males fully as capable as brown-skinned women.
A second type of evidence that we're not controlled by innate programs is that normal infants taken from one society and reared in another inevitably acquire the behaviors (including language) and competences of the society in which they are reared. If different behaviors in different societies were largely genetically programmed, that could not happen. That culture dominates in creating intergroup differences is also indicated by the distribution of genetic differences among human beings. The vast majority (an estimated 85 percent) is not between "races" or ethnic groups but between individuals within groups. Human natures, again, are products of similar (but not identical) inherited endowments interacting with different physical and cultural environments.
Thus, the genetic "make-brain" program that interacts with the internal and external environments of a developing person doesn't produce a brain that can call forth only one type of, say, mating behavior--it produces a brain that can engage in any of a bewildering variety of behaviors, depending on circumstances. We see the same principle elsewhere in our development; for instance, human legs are not genetically programmed to move only at a certain speed. The inherited "make-legs" program normally produces legs that, fortunately, can operate at a wide range of speeds, depending on circumstances. Variation among individuals in the genes they received from their parents produces some differences in that range (in any normal terrestrial environment, I never could have been a four-minute miler--on the moon, maybe). Environmental variation produces some differences, too (walking a lot every day and years of acclimatization enable me to climb relatively high mountains that are beyond the range of some younger people who are less acclimatized). But no amount of training will permit any human being to leap tall buildings in a single bound, or even in two.
Similarly, inherited differences among individuals can influence the range of mental abilities we possess. Struggle as I might, my math skills will never approach those of many professional mathematicians, and I suspect that part of my incapacity can be traced to my genes. But environmental variation can shape those abilities as well. I'm also lousy at learning languages (that may be related to my math incompetence). Yet when I found myself in a professional environment in which it would have been helpful to converse in Spanish, persistent study allowed me to speak and comprehend a fair amount of the language. That was possible even long after I had passed the years during which a new language is easiest to acquire--even if I couldn't teach my tongue to pronounce choh-koh-lah-tay properly. But there are no genetic instructions or environmental circumstances that will allow the development of a human brain that can do a million mathematical calculations in a second. That is a talent reserved for computers, which were, of course, designed by human minds.
Are there any behavioral instructions we can be sure are engraved in human DNA? If there are, at least one should be the urge to have as many children as possible. We should have a powerful hereditary tendency to maximize our genetic contributions to future generations, for, as we'll see in the next chapter, that's the tendency that makes evolution work. Yet almost no human beings strictly obey this genetic "imperative"; environmental factors, especially cultural factors, have largely overridden it. Most people choose to make smaller genetic contributions to the future--that is, have fewer children--than they could, thus figuratively thwarting the supposed maximum reproduction "ambitions" of their genes. If genes run us as machines for reproducing themselves, how come they let us practice contraception? We are the only animals that deliberately and with planning enjoy sex while avoiding reproduction. We can and do "outwit" our genes--which are, of course, witless. In this respect, our hereditary endowment made a big mistake by "choosing" to encourage human reproduction not through a desire for lots of children but through a desire for lots of sexual pleasure.
There are environments (sociocultural environments in this case) in which near-maximal human reproduction has apparently occurred. For example, the Hutterites, members of a Mennonite sect laving on the plains of western North America, are famous for their high rate of population growth. Around 1950, Hutterite women over the age of forty-five had borne an average of ten children, and Hutterite population growth rates exceeded 4 percent per year. Interestingly, however, when social conditions changed, the growth rate dropped from an estimated 4.12 percent per year to 2.91 percent. Cultural evolution won out against those selfish little genes.
Against this background of how human beings can overwhelm genetic evolution with cultural evolution, it becomes evident that great care must be taken in extrapolating the behavior of other animals to that of human beings. One cannot assume, for example, that because marauding chimpanzees of one group sometimes kill members of another group, selection has programmed warfare into the genes of human beings (or, for that matter, of chimps). And although both chimp and human genetic endowments clearly can interact with certain environments to produce individuals capable of mayhem, they just as clearly can interact with other environments to produce individuals who are not aggressive. Observing the behavior of nonhuman mammals--their mating habits, modes of communication, intergroup conflicts, and so on--can reveal patterns we display in common with them, but those patterns certainly will not tell us which complex behaviors are "programmed" inalterably into our genes. Genetic instructions are of great importance to our natures, but they are not destiny.
Excerpted from Human Natures by Paul R. Ehrlich Copyright © 2002 by Paul R. Ehrlich. Excerpted by permission.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
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1. Evolution and Us
2. Tales from the Animal House
3. Our Natures and Theirs
4. Standing Up for Ourselves
5. Bare Bones and a Few Stones
6. Evolving Brains, Evolving Minds
7. From Grooming to Gossip?
8. Blood's a Rover
9. The Dominance of Culture
10. From Seeds to Civilization
11. Gods, Dive-Bombers and Bureaucracy
12. Lessons from Our Natures
13. Evolution and Human Values Notes References Acknowledgments Index
Hilary Rose and Steven Rose are the editors of Alas, Poor Darwin: The Case Against Evolutionary Psychology, a volume of essays from a diverse array of scientists, social scientists, and humanists cautioning against overly simplistic, global interpretations of evolutionary psychology. Contributors include Mary Midley, Stephen Jay Gould, and Anne Fausto-Sterling.
Sarah Blaffer Hrdy is the author of the landmark study Mother Nature: Maternal Instincts and How They Shape the Human Species, now available in paperback. Hrdy is committed to the insights gained from sociobiology, which encompass evolutionary adaptation from our deep mammalian past, as well as strategies developed in recent human cultural history.
Paul Ehrlich, author of Human Natures: Genes, Cultures, and the Human Prospect, has been at the forefront of many environmental issues, most notably the problem of human overpopulation. Ehrlich brings together the latest insights from several scientific disciplines to argue that the idea of a single "human nature" is illusory and even dangerous when it seems to preclude human flexibility in the face of changing environments. Instead, Ehrlich posits multiple human natures in both the past and the present and believes that humanity does possess the capacity to change its more destructive behaviors.
Barnes & Noble.com: Evolutionary psychology (which believes the psychology of modern humans to be a legacy of an "environment of evolutionary adaptedness," usually identified as the Pleistocene Era), along with related theories linking biology with behavior (genes "for" character traits, how hormones color thought processes, and so on), has been gaining more public awareness recently. Criticisms of these theories are emerging along with their popularity.
What messages do you think the general public is receiving about these theories, and how does that differ from how the scientific community sees them?
Hilary and Steven Rose: There is a host of popular books and newspaper articles offering us genetic explanations for everything from alleged "human universals," such as men's sexual preferences for younger women, to alleged "human differences," such as "religiosity" or "tendency to midlife divorce." So-called evolutionary and genetic explanations thus offer to explain who we are and why we do what we do with the same simpleminded confidence of fundamentalist religions. They offer secular certainty in an uncertain world. Of the 19th-century secular giants, Marx and Freud are dead (well, maybe only resting); today, central stage is given to Darwin. This confidence makes evolutionary and genetic explanations immensely attractive. They draw their energy from the undoubted technological successes of the new molecular genetics and the powerful advocacy of gifted writers. However, among social and life scientists there is much greater skepticism about the all-embracing nature of such claims. Vast speculative edifices are piled onto minimal foundations of often questionable or controversial data. The complexity of the natural and social worlds, and the sheer difficulty of studying ourselves as humans -- a difficulty researchers understand only too well -- is swept aside by the Catch-22 theories of evolutionary psychology and behavior genetics in favor of the seductions of universal theory-making.
Sarah Blaffer Hrdy: I agree with Hilary and Steve Rose about the complexity of social behavior. It was partly in response to criticisms by the Roses and others that sociobiologists started paying more attention to development, social context, and, especially, local history. In Mother Nature I examine the contingent nature of maternal responses according to the circumstances in which each woman finds herself.
Thinking in terms of human universals like "instinctive mother love" is just not very helpful when considering the extraordinarily variable levels of maternal commitment found over the course of human history. Some mothers are extraordinarily committed to their infants; others abandon them at birth. Clearly, we need to pay attention to ecological and social context and local history. Frankly, I have very little to say about genes, because at this point, our knowledge of the genetic basis of particular maternal responses is extremely limited.
Sure, it is important to know that a genetically engineered mouse lacking a specific fosB gene fails to gather her pups into her nest. But it is even more important to recognize what a very small part of the nurturing enterprise is accounted for by this gene and to recognize the importance of the context in which maternal behaviors are unfolding.
And yes, alas, this kind of information gets picked up by popularizers who make headlines with stories about a gene for the "essence of mothering." But this does not mean that scientists should avoid big questions like the biological bases of maternal love. It simply means that we need to be more careful about the claims that we make.
Pretentious and dogmatic claims by some evolutionary psychologists bother me just as much as they bother the Roses. But the answer is not to shut down research and theorizing. Distorted claims about "human nature" have been around a lot longer than any particular research enterprise. They predate Darwin, predate sociobiology, and predate evolutionary psychology. They are not going to go away anytime soon. What we need then is wider reading of the evidence by more people -- scientists and general readers alike -- educated to think critically and evaluate complex information.
Luckily for Darwin, this is happening.
Paul Ehrlich: I think that evolutionary psychologists are long on psychology and short on evolution. The public increasingly has the impression that genes control our behavior. Nonetheless, it's crystal clear from the fact that there are roughly 1 billion synapses in our brains for every gene that most details of our behavior (controlled by those synapses) must be programmed from information in the environment, including much of it during our long, helpless infancy. The EPs clearly don't understand how difficult it is for selection to do just one thing -- such as program into women's brains how rich a man should be to attract a woman or into men's brains the age spread of targets for rape. Just consider the famous Siamese twins Cheng and Eng. They had identical genomes, yet differed in personality and politics, and one was a drunk and the other sober. Unhappily, we know very little about environmental/cultural programming of the brain's connections except for some very basic things like sight, but the subtleties of the process are once again illustrated by Cheng and Eng, who lived their lives in environments just inches apart and yet became so different. They were doubtless the most important things in each other's environment, and, presumably, small initial differences, perhaps from different positions in the womb, escalated. The importance of the uterine environment is also suggested by the apparent ability of small differences in hormone fluxes to change gender identity.
The potency of environment in behavior is exemplified by the use of contraception. If we're genetically "programmed" for anything it's to outreproduce our colleagues. Differential reproduction of genetic types is the essence of natural selection. And yet no human population maximizes its reproduction -- we outwit our "selfish genes" (of course genes are neither "selfish" nor "self-replicating"). Other evidence comes from cross-fostering -- infants adopted into nonbirth cultures acquire flawlessly the language and other behaviors of the adoptive culture. Indeed, the big challenge for geneticists and brain scientists is to figure out which interesting behaviors (short of those, for instance, traceable to us being "sight" animals) actually are strongly influenced by our genomes. We know from behavioral changes in diseases like Down syndrome that genes contribute to behavior along with environment, but we don't really understand the interactions -- indeed, the "nature-nurture" dichotomy is false, a necessary simplification for analysis. My candidate for an interesting behavior that must clearly have a substantial genetic component is the establishment of kinship systems.
In summary, following Ed Wilson's pioneering work countering Watsonian behaviorism, the pendulum has swung much too far to the genetic determinism side -- at least in the United States. We need a corrective. I agree with what my colleagues Sarah Hrdy and Hilary and Steve Rose say.
B&N.com: What do you believe is the most significant point you make in your books compared to the rest of the literature, broadly speaking, on the topic of biology and culture?
H&SR: Let's begin with a self-criticism. The subtitle of our book does not fully express our agenda; it is not just against but beyond EP. To understand what it means to be human in the 21st century requires a rich interchange and friendly discussion among many different disciplines, social, psychological, and biological. We need to transcend the tired old dichotomies of nature versus nurture, genes versus environment, innate versus learned -- and, indeed, biological versus social -- dump them back into the 19th-century discourse within which they belong. The sciences we need for the 21st century will be those that explore the ways in which life -- for all living organisms, but especially for humans -- is a continuous process of becoming -- of constructing ourselves out of the raw material of our evolutionary past -- personal development, and, for humans, our historical, cultural, and social context. This is an ambitious agenda, and one that runs the risk of sounding vacuous against what seem to be the hard-nosed certainties of genetic determinism. Yet contrasting our vision with that offered by, for instance, evolutionary psychology and selfish genery helps us to see the shape of the questions that these new sciences must answer. Sarah Hrdy's feminist sociobiology is working along similar tracks. Specially welcome is her denunciation of the misuse of her Langur monkey studies to justify the adaptationist claims for human stepfather killers.
It has been a pleasure to take part in a discussion with a group of authors who, starting from very different places, nonetheless find ourselves engaged in a shared breakout from the intellectual prison of the "biology as destiny" of EP.
SBH: The novelist David Lodge once complained that literature was all about sex without children, but that life was the other way around. Well, that's how I felt reading the literature on human evolutionary psychology. So much attention accorded to men competing among themselves for mates, with some attention paid to how men and women choose their mates, but almost nothing about parenting and even less about babies. Yet, unless matings result in conceptions that yield offspring that in turn survive to reproduce, from an evolutionary perspective all the sex is just so much sound and contortion, signifying nothing. So what about all the effort, trade-offs, juggling, and strategizing that go into keeping offspring alive and seeing that they prosper? So far as women are concerned, these are the selection pressures that really matter, and ditto for offspring of both sexes. So I decided to write a book about mothers, infants, and allomothers (all the individuals of both sexes who get enlisted to help rear infants) that would encompass a whole range of perspectives. I wanted the book to be comparative and evolutionary but also to reflect developmental, ecological, and historical perspectives, because this is what it takes to understand human behavior, an awareness of both our deep and our more recent history.
PE: I think the most significant thing in Human Natures is the emphasis on the critical role of cultural evolution (changes in the vast store of nongenetic information in our brains, books, films, computers, artifacts, etc.) in determining our behavior -- our "natures." We need to understand the process of cultural evolution much more thoroughly if we are going to end the escalating assault on human life-support systems and chart a route to a sustainable society. Since we can't do much to direct our genetic evolution -- we don't know how, and natural selection is too slow to operate in time -- our main option is to consciously modify cultural evolution. We've made some cheering progress -- as in lowering birthrates and raising environmental consciousness -- but we've a long way to go. Greater understanding of the cultural evolutionary process would smooth our way.
About the Authors
Hilary Rose is a research professor of sociology at City University in London. Steven Rose is a neuroscientist and professor of biology at the U.K.'s Open University. They are joint Professors of Physic at Gresham College, London.
Sarah Blaffer Hrdy is a professor emeritus of anthropology at the University of California at Davis and has been elected to both the National Academy of Sciences and the American Academy of Arts and Sciences.
Paul R. Ehrlich is Bing Professor of Population Studies and Professor of Biological Sciences at Stanford University. Author of The Population Bomb and Betrayal of Science and Reason, among many other books, Ehrlich is a member of the National Academy of Sciences and a recipient of the Crafoord Prize, the Blue Planet Prize, and numerous other international honors.
Posted September 11, 2000
Man's evolutional place in the world has been studied for centuries through the sciences of anthropology, biology, geology, genetics, paleontology and a host of others, and this book does a masterful job of bringing these together. What it does that is different, is describe the evolution of culture: politics, religion, art, language, and other features of the upright-walking primate's life not so easily reduced to scientific explanation. Combining these two approaches to man's current predicament, Professor Ehrlich points out that 'the increasing ability to do things has outstripped the evolution of our ability to understand ... the full implications of what we are now doing,' and with this approach, examines what is happening to us as individuals, to the human community, and to the environment in which we live. If you read one new book this year about man's place in the earth's past, present and future, this is the one.Was this review helpful? Yes NoThank you for your feedback. Report this reviewThank you, this review has been flagged.