"I doubt whether anyone will write as good a book of this sort on [human evolution] for another two or three decades." Sicence
Human Natures: Genes, Cultures, and the Human Prospectby Paul R. Ehrlich
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.
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Genes, Cultures, and the Human Prospect
By Paul R. Ehrlich
ISLAND PRESSCopyright © 2000 Paul R. Ehrlich
All rights reserved.
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 she replied, "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 horrific 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 François 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.
Excerpted from Human Natures by Paul R. Ehrlich. Copyright © 2000 Paul R. Ehrlich. Excerpted by permission of ISLAND PRESS.
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What People are Saying About This
"I doubt whether anyone will write as good a book of this sort on [human evolution] for another two or three decades." Sicence
Meet the Author
Paul R. Ehrlich is the Bing Professor of Population Studies and Professor of Biological Sciences at Stanford University. His books include the bestselling The Population Bomb, and he is a member of the National Academy of Sciences and a recipient of numerous international honors. Ehrlich lives in Stanford, California.
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