We emphasize biological influences on human behavior not because they are more important than environmental influences but because they need to be emphasized, for while no human behavior is 100 percent determined by the genes, neither is any human behavior 100 percent determined by the environment. The former is not controversial; everybody knows it. The latter is controversial, and not enough people know it. That is why we emphasize it in this book.
Evolutionary psychology is the new science of human nature and, together with behavior genetics, is currently the best theoretical perspective with which to understand the biological and evolutionary influences on human preferences, values, emotions, cognition, and behavior.4 In this book, we try to introduce evolutionary psychology to a wider audience. While evolutionary psychology is sweeping the social and behavioral sciences, there have been relatively few recent popular introductions to the field.[5] Because there are a large number of fascinating studies published every year in evolutionary psychology, popular introductions must be updated every so often.
In doing so, we adopt a question-and-answer format. We try to use evolutionary psychology to address and explain typical experiences in our daily lives as well as events and problems in the larger society, because we believe insight from evolutionary psychology can shed new light on and provide novel solutions to some old problems. This is, if you will, an evolutionary psychology question-and-answer book.
We also want to demonstrate in this book that evolutionary psychology is not just about sex and mating. While there have been many fascinating studies in evolutionary psychology about sex and human mating (and we will discuss them in chapter 3), we believe evolutionary psychology can explain much more about human behavior. In fact, we want to show that insight from evolutionary psychology is useful in explaining puzzles in all areas of human life. This is the reason we adopt the question-and-answer format and address many areas of human social life in this book.
Two Errors in Thinking That We Must Avoid
In any discussion of evolutionary psychology, it is very important to avoid two serious mistakes in thinking. They are called the naturalistic fallacy and the moralistic fallacy. The naturalistic fallacy, which was coined by the English philosopher George Edward Moore in the early twentieth century6 though first identified much earlier by the Scottish philosopher David Hume,7 is the leap from is to ought—that is, the tendency to believe that what is natural is good; that what is, ought to be. For example, one might commit the error of the naturalistic fallacy and say, “Because people are genetically different and endowed with different innate abilities and talents, they ought to be treated differently.”
The moralistic fallacy, coined by the Harvard microbiologist Bernard Davis in the 1970s,8 is the opposite of the naturalistic fallacy. It refers to the leap from ought to is, the claim that the way things should be is the way they are. This is the tendency to believe that what is good is natural; that what ought to be, is. For example, one might commit the error of the moralistic fallacy and say, “Because everybody ought to be treated equally, there are no innate genetic differences between people.” The science writer Matt Ridley calls it reverse naturalistic fallacy.9
Both are errors in thinking, and they get in the way of progress in science in general, and in evolutionary psychology in particular. However, as Ridley astutely points out, political conservatives are more likely to commit the naturalistic fallacy (“Nature designed men to be competitive and women to be nurturing, so women ought to stay home to take care of their children and leave politics to men”), while political liberals are equally likely to commit the moralistic fallacy (“The Western liberal democratic principles hold that men and women ought to be treated equally, and therefore men and women are biologically identical and any study that demonstrates otherwise is a priori false”). Since academics, and social scientists in particular, are generally left-leaning liberals, the moralistic fallacy has been a much greater problem in academic discussions of evolutionary psychology than the naturalistic fallacy. Most academics are above committing the naturalistic fallacy, but they are not above committing the moralistic fallacy.
We will avoid both errors—both leaps of logic—in this book by never talking about what ought to be at all and only talking about what is. It is not possible to make either mistake if we never talk about ought. We will not draw moral conclusions from the empirical observations we describe in subsequent chapters, and we will not be guided in our observations by moral principles.
There are only two legitimate criteria by which you may evaluate scientific ideas and theories: logic and evidence. Accordingly, you may justifiably criticize evolutionary psychological theories (including those presented in this book) if they are logically inconsistent within themselves or if there is credible scientific evidence against them. As scientists, we will take all such criticisms seriously. However, it would hardly be appropriate to criticize scientific theories simply because their implications are immoral, ugly, contrary to our ideals, or offensive to some. We can tell you right now that the implications of many of the ideas we present in this book (whether ours or someone else’s) are indeed immoral, ugly, contrary to our ideals, or offensive to either men or women (or some other groups of people). However, we must state them as they are because, to the best of our scientific judgment, they are true. That does not mean that we endorse all possible consequences and implications of our observations or believe that they are somehow good, right, desirable, or justifiable.
Truth is the guiding principle in science, and it is the most important thing for scientists. We also believe that any solution to a social problem must start with the correct assessment of the problem itself and its possible causes. We can never devise a correct solution to a problem if we don’t know what its ultimate causes are. So the true observations are important foundations of both basic science and social policy.
A Note about Stereotypes
It would be tempting to dismiss many of our observations (such as answers to questions like, “Why are there so many deadbeat dads but so few deadbeat moms?” or “Why are almost all violent criminals men?”) as stereo types. We plead guilty to the charge; many of our (and others’) observations are stereo types. But we suggest that you cannot dismiss an observation by calling it a stereo type, as if that suddenly makes it untrue and thus unworthy of discussion and explanation. In fact, the opposite is the case. Many stereo types are empirical generalizations with a statistical basis and thus on average tend to be true. The only problem with stereo types and empirical generalizations is that they are not always true for all individual cases. There are always individual exceptions to stereo types. There are many dedicated fathers and female criminals, even though the generalizations are still true. The danger lies in applying the statistical generalizations to individual cases, which may or may not be exceptions.
Stereo types have a bad name, but many of them may turn out to be true empirical generalizations that someone does not like or that are unkind or offensive to some groups. An observation, if true, becomes an empirical generalization until someone objects to it, and then it becomes a stereo type. For example, the statement “Men are taller than women” is an empirical generalization. It is in general true (and, by the way, there are evolutionary psychological explanations for this phenomenon10), but there are individual exceptions. There are many men who are shorter than the average woman, and there are many women who are taller than the average man, but these exceptions do not make the generalization untrue; in every human society, men on average are taller than women. Everybody knows this, but nobody calls it a stereo type because it is not unkind to anybody. Men in general like being taller than women, and women in general like being shorter than men.11
However, as soon as one turns this around and makes the slightly different, yet equally true, observation that “Women are fatter than men,” it becomes a stereo type because nobody, least of all women, wants to be considered fat. But it is true nonetheless; women have a hi
gher percentage of body fat than men throughout the life course (and there are evolutionary reasons why this is the case as well12). Once again, there are numerous individual exceptions, but the generalization still holds at the population level.
In this book, we will attempt to make and then explain observations and phenomena that the available scientific evidence indicates are empirically true, even though there are individual exceptions and regardless of whether they may seem unkind to some groups (which they may in many cases). We draw no consequences or conclusions out of such observations; we are simply stating and explaining them. We will not commit either naturalistic or moralistic fallacy. Stereo types and empirical generalizations are neither good nor bad, desirable nor undesirable, moral nor immoral. They just are.
Stereo types also do not tell us how to behave or treat other people (or groups of people). Stereo types are observations about the empirical world, not behavioral prescriptions. One may not infer how to treat people from empirical observations about them. Stereo-types tell us what groups of people tend to be or do in general; they do not tell us how we ought to treat them. Once again, there is no place for “ought” in science.
How to Use This Book
The book is organized so that after the introduction and two introductory chapters, readers may skip around and read whichever chapters and sections are of interest. Each chapter (and section within it) is designed to be self-contained for anyone who has read the introduction and the first two chapters. We introduce fundamental principles of evolutionary psychology in chapters 1 and 2. Chapters 3–8 cover different areas of everyday life (sex and mating, marriage, family, crime and violence, political and economic inequalities, and religion and conflict). In each we pose several questions readers may have wondered about in their own lives, and provide evolutionary psychological answers to them. We look ahead at the questions that still remain unanswered by evolutionary psychology in the conclusion.
All of our claims are fully referenced to scientific studies that provide supportive evidence. For endnotes that simply give citation information, we use the standard endnote reference numbers, for example.1 References that give greater information not contained in the text have reference numbers with brackets, for example.[2]
1
What Is Evolutionary Psychology?
Evolutionary psychology is a new, emerging field. The first landmark studies in evolutionary psychology were published in the late 1980s,1 and the birth of modern evolutionary psychology was marked in 1992 with the publication of the tome The Adapted Mind: Evolutionary Psychology and the Generation of Culture,2 which is often regarded as the bible of modern evolutionary psychology.3 What was there before then? Before we tackle the question, “What is evolutionary psychology?” in this chapter, let’s pause a moment to consider what theories and explanations were available to social scientists before its advent.
A Typical View from the Social Sciences
Most social scientists explain human behavior in a more or less typical fashion. The particular school of thought is called “the Standard Social Science Model.”4 Because social scientists and their theories tend to have a lot of influence on the general public, the same view also characterizes how ordinary people account for human behavior in their everyday lives.
What exactly is the Standard Social Science Model? A set of related principles characterize its main tenets.
1. Humans are exempt from biology. Social scientists who subscribe to the Standard Social Science Model know that biology (and its branches, like zoology, ornithology, and entomology) can explain the behavior of all other species in nature. Yet they make an exception for humans as a sole species whose behavior is not explained by biological principles and theories. Human exceptionalism is the hallmark of the Standard Social Science Model. Many social scientists have averse reactions to biological explanations of human behavior.5 This principle says that humans are exceptions in nature.
2. Evolution stops at the neck.6 Social scientists in the Standard Social Science Model tradition, who do not believe in biological influences on human behavior and cognition, nonetheless acknowledge that human anatomy has been shaped by evolution. They recognize that human body parts, such as the fingers and the toes, are the way they are because of a long evolutionary process of natural and sexual selection. However, they contend that evolution has had no effect on the contents of the human brain and the human mind. This principle says that the brain is an exception in the human body.
3. Human nature is tabula rasa (a blank slate).7 As a result of principle 2 above, social scientists in the Standard Social Science Model tradition contend that humans are born with a mind like a blank slate. Once again, they recognize that all the other species have innate natures: dogs have an innate dog nature, which makes them behave more or less the same no matter where they live or what their individual life experiences have been, and cats have an innate cat nature, which similarly makes them behave the same but different from dogs. The same goes for all species in nature—except for humans. Humans do not have an innate nature, as they are born with minds that are blank slates. Principle 3, like principle 1, is an example of human exceptionalism.
4. Human behavior is a product almost entirely of environment and socialization. Since, according to the Standard Social Science Model, humans have no innate human nature that guides their behavior, the contents of human nature must be written after birth. The Standard Social Science Model contends that this occurs by a lifelong process of socialization (learning via instruction, imitation, copying, etc.) by the agents of socialization (parents, other family members, teachers, other adults in society, the media). Humans become the way they are because of socialization; socialization makes them human. In particular, men and women acquire their typical male and female behavior through gender socialization. This is why another name for the Standard Social Science Model is environmentalism. Most social scientists believe that the environment and life experiences almost entirely shape and determine human behavior.
Admittedly, this is a somewhat simplified version of the Standard Social Science Model, but it is not far off the mark. Not all social scientists agree with all of the four tenets, but most would agree with most of them to a large extent (and many agree with all).8 Recent surveys of introductory textbooks in sociology and psychology reveal very cursory (and often incorrect) discussions of human evolution and its effect on behavior.9
The Evolutionary Psychological Perspective[10]
Let us now look at the basic principles of evolutionary psychology. You could not possibly miss the sharp contrast between the Standard Social Science Model and evolutionary psychology.
As we said in the introduction, evolutionary psychology is the study of human nature. While the phrase “human nature” is used in common discourse to mean something essential but otherwise undefined about being human, it has a specific meaning in evolutionary psychology. It refers to a collection of components called evolved psychological mechanisms or psychological adaptations (these two terms are roughly synonymous). Human nature is the sum of such evolved psychological mechanisms, and evolutionary psychologists aim to discover more and more such psychological adaptations in humans. What, then, is an evolved psychological mechanism or psychological adaptation?
Evolved Psychological Mechanisms: What Human Nature Is Made Of
An adaptation is a product of evolution by natural and sexual selection,[11] and it allows an organism to solve particular problems.12 Our body is full of adaptations. Our eye is an adaptation; it allows us to see, navigate efficiently and safely, find prey, and avoid predators. Our hand is an adaptation; it allows us to hold and manipulate objects efficiently, collect and eat food, throw objects, and use and manufacture tools. If you imagine what your life would be like without an eye or a hand, you can begin to see the range of problems that these physical adaptations solve. Problems that adaptations allow us to solve are called adaptive problems. Adaptive problems are problems of survival and repr
oduction. Without solving adaptive problems, we will not be able to live long or reproduce successfully.
Psychological adaptations are like these physical adaptations in our body, except they are in our brain. They allow us to solve some adaptive problems by predisposing or inclining us to think or feel in certain ways. Just like we see or manipulate objects without much conscious thought, psychological adaptations often operate behind and beneath our conscious thinking. All adaptations (physical and psychological) are also domain-specific; they operate and solve problems only within a narrow area of life. The eye allows us to see but not manipulate objects; the hand allows us to manipulate objects but not see them. What the eye can do, the hand cannot, and vice versa. This is true for evolved psychological mechanisms as well; they only operate and solve problems in a narrow range of life.
Our preference for sweets and fats is an example of an evolved psychological mechanism.13 Throughout most of human evolutionary history, getting enough calories was a serious problem; malnutrition and starvation were common. In this environment, those who, for reasons of random genetic mutation, had a “taste” for sweets and fats, which contain higher calories, were better off physically than those who did not have such a taste. Those who had a sweet tooth therefore lived longer, led healthier lives, and produced more healthy offspring than those who did not. They in turn passed on their (genetically influenced) taste to their offspring, over many thousands of generations. In every generation, those with this taste out-reproduced those without it, generation after generation, until most of us living today have a strong preference for sweets and fats.
Why Beautiful People Have More Daughters: From Dating, Shopping, and Praying to Going to War and Becoming a Billionaire–Two Evolutionary Psychologists Explain Why We Do What We Do Page 2