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Do you think God knew what he was doing...or do you think it was just another of his minor mistakes--like tidal waves, earthquakes, floods....When we make mistakes, they call it evil; God makes mistakes, they call it nature.
A mistake? Or did he do it on purpose? Because if it's a mistake, maybe we can do something about it--find a cure; invent a vaccine; build up our immune system.
Throughout most of human history, the answers to these questions have come from myth or literature. Starting with the Enlightenment, however, the answers have usually been couched in the allegedly "objective findings" of either history or science. Since the end of World War II, the "standard model of social science," as summarized by Robert Wright in his very readable introduction to evolutionary psychology, skeptically (if not cynically) titled The Moral Animal, has held that "the uniquely malleable human mind, together with the unique force of culture, has severed our behavior from its evolutionary roots;...[and] there is no inherent human nature driving events...our essential nature is to be driven" (1994, p. 5).
For example, Emile Durkheim, the patriarch of modern sociology, referred to human nature as "merely the indeterminate material that the social factor molds and transforms." He argued that even such deeply felt emotions as sexual jealousy, a father's love of his child, or the child's love of the father are "far from being inherent in human nature." Robert Lowie, a founding father of American cultural anthropology, argued that "the principles of psychology are as incapable of accounting for the phenomena of culture as is gravitation to account for architectural styles." Ruth Benedict, one of the founding mothers of American anthropology, and a crusader against the theory of racial differences (which was the norm in pre-World War II days), wrote that "we must accept all the implications of our human inheritance, one of the most important of which is the small scope of biologically transmitted behavior, and the enormous role of the cultural process of transmission of tradition." (All quotes from Wright, 1994.) B. F. Skinner founded the school of behavioral psychology, dominant in American psychology in the 1950s and 1960s, on the bedrock assumption that human and animal behavior could be accounted for in terms of rewards and punishments.
To all of this, evolutionary psychologists reply with the gusto of a Wayne and Garth "NOT!" Human nature is real, it is important, and it isn't going to go away. Here is a sampling of the sorts of questions evolutionary psychologists ask and attempt to answer:
Are such questions even scientifically meaningful or do they more properly fall in the realms of religion, literature, or politics? They are certainly great openers to liven up even the dullest party. But the new and emerging field of evolutionary psychology, building on work from Charles Darwin's Descent of Man and The Expression of Emotion in Man and Animals, tells us that the answers to these age-old questions, dear Brutus, are in our evolutionary history and our genes. And they claim they've got the "bloody daggers" to prove it!
This introduction cannot examine the evolutionary argument on each of these points. Instead, it merely outlines the case and describes the type of evidence and the nature of the arguments to be placed before you, the skeptical jury. The references in the bibliography provide a more complete "transcript." Our symposiasts will then present their closing arguments for and against evolutionary explanations of human behavior.
The fundamental theorem upon which evolutionary psychology is based is that behavior (just like anatomy and physiology) is in large part inherited and that every organism acts (consciously or not) to enhance its inclusive fitness--to increase the frequency and distribution of its selfish genes in future generations. And those genes exist not only in the individual but in his or her identical twin (100%), siblings (on average, 50%), cousins (on average, 25%) and so on down the kinship line. (Thus, aid to and feelings for relatives makes evolutionary sense.)
This revision and extension of Darwinian evolution, from "survival of the fittest" to inclusive fitness, was worked out primarily by George Williams (in the US) and by William Hamilton and John Maynard Smith (in the UK) in the 1960s, with some clever twists added by Robert Trivers (in the US) in the 1970s. How efficiently can the Darwinian mill grind they asked? It largely depends on the type of grain fed in. Darwinian selection operates most effectively if the units on which it is working:
Richard Alexander (1979) has argued convincingly that "genes are the most persistent of all living units, hence on all counts the most likely units of selection. One may say that genes evolved to survive by reproducing, and they have evolved to reproduce by creating and guiding the conduct and fate of all the units above them" (p.38, emphasis Alexander's).
Implicit in this reasoning is the conclusion that species and populations (races) are very unlikely units of selection. Hence, all talk of individuals doing things, especially dying, for the good of the species or the race, appear improbable if not downright impossible. But if that is the case, then how could any sort of cooperative behavior, of which there are as many examples all around us as there are of competitive behavior, have ever evolved?
Well, humans, like most complex species, don't pass on their genes by simply dividing and producing exact replicas of themselves the way amoebas do. It takes at least two, not only to tango, but to reproduce. While you need not share any genes with your mate, you must share some, but not necessarily all of them with your relatives (except in the interesting case of an identical twin, who shares all your genes). Work out the arithmetic and it produces some interesting consequences in terms of whom you should help and when, as summarized in Figure 1 (adapted from Alexander, 1979). Rather than anything so simple as either "every man for himself" or "all for one and one for all," Figure 1 shows that, like it or not, you're stuck in a complex, time-directed matrix of cooperation, competition, trust, and deception with all your blood relatives and even those you might think are blood relatives.
Appropriately enough, you watch out for Number 1 first; your parents, children, and full siblings next; and so on in order of decreasing genetic similarity. But given that time's arrow flies in one direction only, you have a better chance of passing on your genes by helping your children than by helping your aging parents.
In The Evolution of Human Sexuality (p. 27, 1979), anthropologist Donald Symons provides evolutionary psychology's point-by-point reply to "the horny little devil's" soliloquy on men and women:
To many, this sets a new standard in arguing for the inherent and therefore inescapable nature of the double standard. What evidence is there to support the argument that male-female differences are so deeply rooted in our nature? Anthropologists Lionel Tiger and Robin Fox argued in 1971 in The Imperial Animal (see interview this issue) that if "we look at enough primates to see what we all have in common, we'll get some idea of what it was we evolved from. If we see what we had to change from to get to be what we are now, it might help to explain what we in fact are."
Figures 2 and 3 are adapted from Jared Diamond's The Third Chimpanzee (pp. 73-74). They compare the relevant male and female anatomy for humans and our nearest living relatives, the great apes.
First look at the amount of sexual dimorphism in the four species. As Diamond notes, "chimps of both sexes weigh about the same; men are slightly larger than women, but male orangutans and gorillas are much bigger than females" (p. 73). These are interesting facts from comparative anatomy, but what do they have to do with behavior? Throughout the animal kingdom, polygynous species (i.e., those in which each dominant male breeds with multiple females), are sexually dimorphic. This makes sense from an evolutionary point of view. The only way a male can pass on his genes is to breed with a female, and to better the odds, the more the merrier. But since there are only so many females to go around, from day 1 males are in competition with other males for those females. An arms race begins in which males are selected for their ability to win out against other males for access to the females. And since nothing escalates like an arms race, you end up with male gorillas and orangs that are not only twice the size of the females, but armed with huge canines, and loaded with secondary sexual characteristics like crested heads and silver backs that are easily recognizable at a distance and help to attract mates.
Chimps, on the other hand, show little sexual dimorphism, less even than humans. The gibbon (an ape, but not a great one) shows the least sexual dimorphism. Males and females look identical at a distance and the gibbons' strict adherence to monogamy should win an award from the Moral Majority (though that would mean acknowledging man's common primate ancestry and therefore ditching creationism). Going simply by the dope sheet of sexual dimorphism, an evolutionary handicapper would bet the rent that Homo sapiens would, by nature, be mildly polygynous. And he'd walk away from the pay window a big winner. A cross-cultural analysis of 853 societies revealed that 83% of them are polygynous. Polygyny occurs frequently, even when legally prohibited. There are an estimated 25,000 to 35,000 polygynous marriages in the US; a study of 437 financially successful American men found that some maintained two separate families, each unknown to the other (Buss, pp. 177-178). Polyandry (one female with multiple males), on the other hand, is "virtually absent" among hunter/gatherers and confined to "agriculturalists and pastoralists living under very difficult economic conditions" and disappears quickly "when more usual conditions are present" (Symons, p. 225).
To move on from gross anatomy to gross discourse, if the male gorilla is so big and tough, how come he has such small balls? How does evolutionary theory account for those differences in testicle, penis, and breast size? It may be a tough climb to the top of the male gorilla dominance pyramid, but once there, things become quieter. Until dethroned, you have virtually uncontested access to all the females, so sex is no big thing. In fact, the dominant male with a harem of females "experiences sex as a rare treat: if he is lucky, a few times a year" (Diamond, p. 73). So just a little bit of sperm goes a long way to insuring the male gorilla's inclusive fitness.
For the minimally sexually dimorphic chimp, things get a little dicier. Chimps do have power pyramids. Compared to the gorilla and the orang, their hierarchies are so complex that Frans de Waal entitled his study of them Chimpanzee Politics. Getting to the top and staying there calls more for the skills of a Machiavelli than of a Mike Tyson. Dominant males have frequent though not exclusive access to the females. Rather than simply their bodies, it is their sperm that must compete against those of their fellow dominants, as well as those of the occasional "sneaky fucker." And all of this follows directly from one of the triumphs of evolutionary biology--The Theory of Testicle Size. To wit, "species that copulate more often need bigger testes; and promiscuous species in which several males routinely copulate in quick sequence with one female need especially big testes (because the male that injects the most semen has the best chance of being the one to fertilize the egg). When fertilization is a competitive lottery, large testes enable a male to enter more sperm in the lottery" (Diamond, p. 72).
Humans, according to evolutionary theory, should therefore be intermediate between chimps and gorillas both in polygyny and in promiscuity--and the data fit the prediction. I leave it to the reader to speculate as to what the evolutionary result would be if groups of religious cultists (in which the leader tries to monopolize the females) and outlaw biker gangs (who after all gave us the term "gang bang") were to each pursue their own evolutionary path, separate from the rest of human society.
Diamond provides more hard anatomical data (p. 75):
The length of the erect penis averages 1-1/4 inches in a gorilla, 1-1/2 inches in an orangutan, 3 inches in a chimp, and 5 inches in a man. Visual conspicuousness varies in the same sequence: a gorilla's penis is inconspicuous even when erect because of its black color, while the chimp's pink erect penis stands out against the bare white skin behind it. The flaccid penis is not even visible in apes.
To date, however, there is no adequate evolutionary explanation of the between-species differences in penis size. J. P. Rushton has offered a very controversial explanation of the mean differences in penis size between various racial groups within the human species. His letter to Skeptic (Vol. 3, No. 4, pp. 22-25), with an accompanying table, summarizes his argument that there is a "tradeoff" between cognitive assets (brain size and IQ score) and reproductive assets (penis size and gamete production). Both neurons and gametes are expensive and Rushton's data are replicable, but most evolutionary biologists and psychologists do not accept his interpretation.
Rushton's work highlights two important differences among evolutionary explanations of behavior. Evolutionary explanations of genetic differences between individuals, and especially between groups of individuals, have an air of an earlier Social Darwinism which many today find downright offensive. Which is not to say that they are, for that reason, factually wrong. But most of today's evolutionary psychologists are concerned with the universals of human nature, not the differences. They argue that "genetic differences among individuals surely play a role, but perhaps a larger role is played by genetic commonalities: by a generic, species-wide developmental program that absorbs information from the social environment and adjusts the maturing mind accordingly." They therefore believe that "future progress in grasping the importance of environment will probably come from thinking about genes" (Wright, p. 9).
And whereas Rushton and others, located on the pro side of The Bell Curve controversy, argue for a unitary view of the mind (usually manifested in a single trait variously referred to as intelligence, IQ, cognitive ability, or psychometric g) on which all individuals (and even groups) can be measured and ranked from top to bottom ("alphabetically by height" as legendary New York Yankee manager Casey Stengel once put it), most of today's evolutionary psychologists argue that evolution would rather select for distinct mental modules. In their view, evolution can give males a "love of offspring" module, and make that module sensitive to the likelihood that the offspring in question is indeed the man's. But the adaptation cannot be foolproof. Natural selection can give women an "attracted to muscles" module, or an "attracted to status" module, and...it can make the strength of those attractions depend on all kinds of germane factors.... As Tooby and Cosmides say, human beings aren't general purpose "fitness maximizers." They are "adaptation executors." The adaptations may or may not bring good results in any given case, and success is especially spotty in environments other than a small hunter-gatherer village (Wright, pp. 106-107).
In the view of most evolutionary psychologists, the modules may differ in effectiveness from one individual to another, but given the number of different modules, their effect is to "average out" individual differences to the point where any attempt to "line everyone up" on a single dimension is as nebulous as Casey's syntax.
Now let's look at the females. "Human females are unique in their breasts, which are considerably larger than those of apes even before the first pregnancy" (Diamond, p. 74). Since the female gorilla and her baby are comparable in size to their human counterparts, the bulk of the huge (by primate standards) human female breast consists of fat, not milk glands, and breast size varies greatly among human females without affecting their ability to nurse young. Thus, the explanation cannot be based on the need to nurse infants. Rather, human female breasts are secondary sexual characteristics that evolved to attract mates. According to Desmond Morris (1967), this took place along with the switch from front-to-rear to front-to-front mating, the pendulous shape and cleavage of the breasts mimicking the pre-existing attractiveness of the female buttocks. This also, according to the theory, explains why men find other pendulous shapes (like ear lobes) and other cleavages (like toes in low-vamped shoes) such a turn-on.
And while we're on the subject, what other female attributes turn men on? Gentlemen prefer young, nubile women, with lips like rubies, eyes like limpid pools, skin like silk, breasts like a milch cow, and legs like a race horse. According to evolutionary theory, this is not the result of either Hollywood or Madison Avenue, but because all of these features have served as cues to a female's health, reproductive potential and sexual availability over the course of human evolutionary history. Evolution has built into every red-blooded male a desire to find "Pornotopia"--the fantasy land where "sex is sheer lust and physical gratification, devoid of more tender feelings and encumbering relationships, in which women are always aroused, or at least easily arousable, and ultimately are always willing" (Symons, p. 171). The entire cosmetics, fashion, and pornography industries are attempts to create Pornotopia here on Earth.
Figure 4, adapted from Daly and Wilson (1988) depicts human female reproductive value, calculated in terms of expected live births among hunter/gatherers, as a function of female age. This curve parallels the curve for men's preferences in females as determined in cross-cultural studies (Buss, pp. 49-60; Symons, pp. 187-200).
Men naturally prefer young women because they provide the most reproductive potential for passing on the male's genes. If anything, males are biased toward selecting females before reproductive age in order to insure that no other male has beaten them to the finish line. From an evolutionary perspective, the least wise thing a male can do is to divert his hard-earned resources to rearing another man's child. Indeed, evolutionary psychologists would argue that this is why cuckolds are universally held in such low regard.
marriage is a contract not between husband and wife, but between men, a formalized transfer of a woman as a commodity. And indeed when one examines the material and labor exchanges that surround marriage, it does begin to look like a trafficking in women. In our society, as in many, a father gives his daughter in marriage. Men purchase wives in the majority of human societies, and they often demand a refund if the bargain proves disappointing. Although the relatively rare practice of dowry might be construed to mean that who pays whom is arbitrary and reversible, dowry and bride-price are not in fact opposites: A bride-price is given as compensation to the bride's kin, whereas a dowry typically remains with the newlyweds.
Figure 5 (adapted from Daly & Wilson, p. 189) summarizes the exchange considerations at marriage in a cross-cultural comparison of 860 societies and emphasizes the universality of compensation for rights to female reproductive capacity.
Even worse from the point of view of the male and his family than failure by the female to live up to her part of the contract is the thought that the male's investment in resources may be going into a competitor's product. Figures 6 and 7 (adapted from Homicide by Daly and Wilson) show that child abuse and even murder are much more common for adoptive parents than for natural parents.
While evolutionary theory predicts a certain level of parent-child and sibling rivalry, its predictions are contrary to another mainstay of social science--the Freudian Oedipus Complex. Under evolutionary theory, fathers have a strong vested interest in their son's well-being; provided, of course, it is their son. As sons mature, they may in fact compete with their fathers for status and for females (as daughters may compete with their mothers for males), but not for their own mother (or father). Many evolutionists argue that, given the decreased viability of children born out of incest, selection has created an incest taboo, especially against mother-son incest. The comparative ethnographic data support the existence of the incest taboo, not the Oedipus complex (Alexander, p.165; Wright, pp. 315-316).
Anthropologist Helen Fisher has gathered divorce data from 62 societies around the world (Figures 8 and 9). She finds that "human beings in a variety of societies tend to divorce between the second and fourth years of marriage, with a divorce peak during the fourth year" (p. 360). She also finds that the divorce statistics for the US in 1986, well past the sexual revolution of the 1960s, fit the same pattern, with most divorces taking place between the second and third year of marriage (p. 362).
Fisher's evolutionary explanation attributes the universality of the divorce statistics to the "remarkable correlation between the length of human infancy in traditional societies, about four years, and the length of many marriages, about four years. Among the traditional !Kung, mothers hold their infants near their skin, breast-feed regularly through the day and night, nurse on demand, and offer their breasts as pacifiers. As a result of this constant body contact and nipple stimulation, as well as high levels of exercise and a low-fat diet, ovulation is suppressed and the ability to become pregnant is postponed for about three years" (p.153). She therefore concludes (p. 154):
The modern divorce peak--about four years--conforms to the traditional period between human successive births--four years....Like pair-bonding in foxes, robins, and many other species that mate only through a breeding season, human pair–bonds originally evolved to last only long enough to raise a single dependent child through infancy, the first four years, unless a second child was conceived.
But just how scientific are these attempts to explain human behavior in evolutionary terms? To what extent do the questions we ask automatically set up the answers we get? After all, as Cassius taunted Brutus, we are sometimes masters of our own fate! To what extent are human nature and individual and group differences scientifically meaningful concepts, rather than the social constructions of learning and experience, political and economic conditions? Is there any scientific there there?
Harry Schlinger, a psychologist at Western New England College, critically analyzes evolutionary theories and argues that human behavior can be more scientifically and parsimoniously explained in terms of the verifiable laws of learning, without recourse to evolutionary or genetic arguments. Harmon Holcomb, a philosopher of science at the University of Kentucky, skeptically examines the theories of evolutionary psychology and finds that for the most part, at this point, they are neither pseudoscience, nor hard science, but protoscience, that is, science in the making. To graduate to the status of true science evolutionary psychology must put forth hypotheses that are capable of being critically disproven, rather than just reinforced or reconfirmed. He is a fair skeptic. Edward O. Wilson wrote on the cover of Holcomb's book Sociobiology, Sex, and Science, "Holcomb is now clearly the leading authority on sociobiology among philosophers of science" and (the book) "can and should be the standard reference on the subject." Reviewing the papers presented at the most recent meeting of the Human Behavior and Evolution Society, he shows which research has reached the level of real science. Frank Salter of the Max Planck Institute supplies a biological counterattack. He critically examines sociology by taking us on a skeptical browse through The Oxford Dictionary of Sociology, and finds that its studied avoidance of basic human nature amounts to little more than modern alchemy.
We round out the symposium with matched pairs of interviews and book reviews. Lionel Tiger and Robin Fox, two of the grand old men of evolutionary theories of behavior, look back on what's taken place in the field in the 25 years since they published their ground-breaking and controversial book The Imperial Animal. Skeptic advisory board member Stephen Jay Gould, a longtime critic of excessive appeals to evolution and genetics in the explanation of human behavior, offers his thoughts on evolution, his own revision of Darwinism, the problems with ultra-Darwinism, and the politics of science. Philosopher of science Michael Ruse, an expert on the nexus between philosophy and biology, reviews one of the most controversial new books in this field--Daniel Dennett's Darwin's Dangerous Idea--which is very critical of those who would revise basic Darwinian explanations, such as Gould with his theory of punctuated equilibrium. Skeptic publisher Michael Shermer also reviews Dennett's book, though from a different perspective than Ruse, in his analysis of "Gould's Dangerous Idea"--contingency, necessity, and the nature of history. And lest we be accused of presenting only the evolutionary side of the argument, we conclude with some comic relief as anthropologist and long-time creationist observer, Tom McIver, takes us on "A Walk Through Earth History: All Eight Thousand Years," in his skeptical tour of the Institute for Creation Research's museum.
So here then, ladies and gentlemen of the jury, is the issue at hand: Should we accept as a default hypothesis that human behavior, and the similarities and differences in behavior between individuals and groups, are the result of a complex interaction of the genes that reflect our evolutionary history as well as the environment in which we find ourselves? Or should we opt for the statistically null hypothesis that any invocation of genes and evolution to explain human behavior must be proved beyond a reasonable doubt? If nothing else, when you finish reading this symposium, I think you will be forced to conclude, in the words of Nobel Prize Winner and co-discoverer of DNA James Watson, that "Charles Darwin will eventually be seen as a far more influential figure in the history of human thought than either Jesus Christ or Mohammed." Counsels for the disputing parties may now proceed.
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