Thus to say that one of the functions of human fingers is to type is absurd to the evolutionary biologist—because typing (indeed any form of writing) was not a part of the environment in which human fingers evolved. Not many anthropologists would make this mistake, but mistakes of a less obvious but similar nature are common enough.
Sometimes the distinction between functions and effects is not as important to the average anthropologist as it is to the evolutionary biologist. Both functions and effects are aspects of human nature, and both provide instances in which the biological impinges upon the cultural or upon human behavior. But there are times when evolutionary reasoning and data have practical relevance.
Consider the following example. Probably all women have the potential of orgasm. But is female orgasm an adaptation? There are two points of view. Symons (1979, 1987b) and Gould (1987) argue that female orgasm is an effect, not a function: like nipples on any male mammal, female orgasm is the nonfunctional homologue of a process that does have a function for the opposite sex. Since the clitoris is not designed to produce female orgasm, that it sometimes does so is an incidental effect (however desirable this effect may be for some individuals). Alcock (1987), by contrast, argues that female orgasm does have a function, as a “Mr. Right detector” (the term is Symons’s). When a woman is with a man who is truly good for her, she will have orgasms.
These different interpretations have very different practical implications. If Alcock is right, anorgasmic women may need to change mates if they really want orgasms; if Symons and Gould are correct, much less drastic steps should suffice. Sex therapist Helen Singer Kaplan (1981) throws some light on the matter by recounting her experience as a sex counselor for anorgasmic poor women at New York’s Metropolitan Hospital. She could not give them long-term treatment and had to dispense the equivalent of instructions on how to run an appliance: she showed them where the clitoris is located and explained how long it takes for arousal. To her surprise, these simple instructions helped approximately 90 percent of her patients. This success rate does not support Alcock’s position.
It must also be kept in mind that adaptations may be either “obligate” or “facultative.” Williams (1966) illustrates these, respectively, with the thickening of the skin on the soles of our feet that is already present at birth, and the thickening of the skin that can occur on many parts of the body when the skin is repeatedly exposed to friction (thus forming a callus). A facultative adaptation is analogous to an implicational universal, and it represents a complex sort of universal potential the manifestation of which is not universally present (genetically it is more complex to program a facultative than an obligate trait).6
Some particularly important adaptations result from sexual selection. Whereas natural selection reflects the fit of an organism to its environment in general, sexual selection specifically reflects fitness in obtaining mates. It has two forms: intersexual selection (often typified by female choice of males) and intrasexual selection (often typified by the male-male competition for access to females). Features that render an organism fit to attract or obtain a mate—the gaudy feathers of the male peacock, for example—may make no sense in terms of adjustment to the wider environment. Whereas natural selection usually accounts for features common to a species, sexual selection often produces differences between the sexes of the same species.
From the viewpoint of social science, one of the most troublesome features of evolutionary biological thought concerns the level at which, or the unit upon which, adaptation occurs. Clearly, genes are selected, and almost equally certainly the phenotypes of individual organisms are selected. But there is substantial agreement among evolutionary biologists that levels of organization higher than that of the individual organism—particularly the level of the group—can rarely if ever be considered as units upon which selection acts. Conservative opinion (e.g., Williams 1966; Maynard Smith 1976) has it that no adaptation should be explained at any higher level than is absolutely necessary: in effect, this means at no level higher than the individual organism. In other words, traits should be explained in terms of the way they make individuals fit, not in terms of group or species benefits. Since social scientists often attribute adaptation, as they understand the term, to the level of the group and the species, this is a point at which biological and social scientists are particularly likely to misinterpret each other—or to disagree.
Before concluding this discussion of evolutionary theory, it is essential to note the role of accident, conservatism, and compromise in evolution. Traits do not necessarily develop because they are needed (even though they are more or less predictable under certain conditions). Traits develop as a result of a random process (gene mutation) that may from time to time confer greater fitness. This random process is the ultimate source of all organic change, but it has no direction. The pressure of environmental circumstances can only, so to say, pick and choose from among mutational accidents. Moreover, under certain circumstances selection may result in adaptations that have a short-term advantage but long-term costs, which further enlarges the role of accident. For a variety of reasons—ranging from molecular and mechanical considerations through those imposed on the constitution of a species by its recent evolutionary history—there are limits on the directions evolution may take. The phylogenetic constraints peculiar to our own species, for example, make it much more likely that smell might become our paramount sense of perception than that we fletch and fly. Finally, genes that confer selective advantages in one respect may have negative consequences in others, so that selection results in many traits that are compromises with each other. Because of these factors, in addition to the (side) effects of adaptations that were mentioned earlier, we cannot expect anything approaching a perfect fit between organism and environment.
There are two further considerations that must be noted in order to make the body of theory that was just presented useful. First, what has been described above concerns “ultimate” or evolutionary explanations (Mayr 1961): how we got the genetic constitution we have. The “proximate” explanations of phylogenetically determined traits often concern matters of anatomy and physiology that a sociocultural anthropologist is usually poorly equipped to study. Perhaps the most familiar example concerns hormones: whatever the ultimate causes of certain male-female differences may be, it is now generally accepted, even in the feminist literature, that an important proximate cause is the differential production of certain hormones in the two sexes. Generally, sociocultural anthropologists utilize this kind of knowledge but are not trained to produce it.
Second, there are certain clues—present in externally observable human behavior—that point toward phylogenetic traits. Clues, of course, are not infallible markers; seeing one or another clue gives us no more than a hunch, or a basis for hypothesizing that some behavioral or psychological pattern was specifically shaped by selection. Because they can serve to guide research, identifying these clues is of utmost importance. Among the most important clues to phylogenetic adaptation are the following: unusual ease (or difficulty) in acquiring specific skills or knowledge, a “critical period” for their acquisition, emotionally motivated actions that run counter to consciously held ideals, unusually intense preoccupation with certain topics, similar behavior among animals, and universality itself, including implicational universality (see Buss 1984 and Boehm 1989 for related clues). Some of these clues have already been discussed and illustrated; others will be illustrated below. We may now turn to specific applications of evolutionary theory.
Kinship
Earlier I suggested that kinship terminologies are universal because kinship is universally important. But what is kinship, and why is it important? Along with mate selection or marriage, the essence of kinship comprises those sentimental attachments that distinguish kin from nonkin and close kin from distant kin. Such nepotistic sentiments are thoroughly familiar features in world ethnography, and careful analyses of adoption (Silk 1980) or domestic homicid
e (Daly and Wilson 1988) document them with some precision.
One of the striking clues to the biological foundation of nepotism is indicated by Meyer Fortes’s (1969) concept of “complementary filiation.” This term was coined to refer to a phenomenon found repeatedly in societies that ideologically reckon kinship either matrilineally or patrilineally. In either case, in spite of the prevailing ideology of descent, an individual typically has strong sentimental ties to those (usually close) genetic kin who are not ideologically reckoned as kin, i.e., some close genetic relatives through the mother in a patrilineal society, through the father in a matrilineal society. By virtue of this phenomenon, the sentimental ties between kin are always to some degree effectively bilateral.
The genetic foundation of nepotism finds its explanation in recent developments in “kin selection” theory (Hamilton 1964; Maynard Smith 1964), which provides one of the solutions to the evolutionary puzzle of how altruism could evolve. In particular, how could altruistic behaviors be adaptations if they are detrimental, or seemingly detrimental, to the survival of one’s own genes? One answer is to point out that behaviors that are directed toward individuals bearing copies of one’s own genes by proximate common descent would be interpersonally altruistic yet potentially result in no reduction of one’s genetic representation in the next generation.
This line of reasoning was worked out particularly to explain the sterile castes of certain insects (bees, ants, and wasps, for example). Among these insects, group livers par excellence, members of the sterile castes seemed to toil and lay down their lives for their fellows without any reproductive benefits for themselves. The realization that the sterile castes served very close kin (all or nearly all having the same mother) made good evolutionary sense of the altruism: if it didn’t benefit themselves individually it did nonetheless benefit carriers of their own genes. The reasoning is no less applicable to humans. For example, the behavior of a man risking his life defending his sister against an abusive husband or by coming to the aid of a brother in a blood feud becomes evolutionarily intelligible if the average result is that, even though the altruist chances to lose his life, his siblings and the offspring of his siblings—all of whom share his genes to a high degree—thereby have an increased chance to survive and reproduce at a rate that results in greater replication of his genes in subsequent generations than if the man left his siblings to fend for themselves.
Precisely how to apply kin selection theory to the elucidation of human affairs has occasioned much debate. A number of anthropologists have operated under the assumption that the human mind is, in effect, a fitness calculator: consciously or unconsciously it weighs the effects of various actions on various degrees of kin and then tends to choose those actions that promote fitness. Consequently, individual actions, and often the customs that presumably have their origin and reality in such actions, make sense as fitness-promoting strategies. Ethnographic materials analyzed in this way have generally not been universals, although the analyses of them rest on the assumption at a high level of generalization that promoting inclusive fitness is universal (e.g., various essays in Chagnon and Irons 1979).
These kinds of analyses have been criticized (Barkow 1984; Cosmides and Tooby 1987; Kitcher 1985; Symons 1989; Tooby and Cosmides 1989c), primarily on the grounds that there is little reason to think that the human mind is a general fitness calculator—even if, in some cases, people act as though they had calculated fitness. That the human mind—or any other mind, for that matter—would evolve such a capacity is one of those features of evolution that one might think ought to occur but probably never has (in principle, according to Cosmides and Tooby [1987], such a mind could not evolve). In the course of their evolution, humans (and other species) did not face generalized problems, they faced specific problems. Consequently, what has evolved (disregarding effects, compromises, accidents, and the like) is a disparate collection of adaptations each separately selected because it contributed to fitness.
This is easily illustrated by an example that will momentarily take us away from nepotism. Symons (1979) argues that the human male is adapted to prefer sex with relatively young women, and in the plural when that is feasible. Under natural conditions, the human male who acted on such impulses—the emotional power of which is universally attested—did much to promote his reproductive success, whether he calculated its reproductive consequences or not. However, in present-day conditions, where effective contraceptive measures are readily available, men are much more content to forgo reproduction than sex. This strongly suggests that the phenotypic mental mechanism(s), upon which selective forces acted, was not the calculation of fitness (too often a matter of indifference to men), but such traits as a propensity to sexual arousal at the sight of nubile women.
Another problem in the application of kin selection theory to anthropological problems concerns the distance at which kinship ties are calculated. It is not at all clear that humans (or any other species) are adapted to distinguish between degrees of distant kin—even though this can be done with genealogical charts and other more scientific procedures that surely were absent in the Palaeolithic. Thus attempts to explain ethnic or racial sentiments as an extension of kin selection (e.g., van den Berghe 1981) have been rightly criticized (Smith 1983).7
What the evidence suggests, therefore, is that those kinship sentiments constituted by phylogenetic adaptation generally work within a narrow range of kin. Three of the most important series of studies of these narrow-based sentiments concern incest avoidance, which will be taken up in chapter 5; male sexual jealousy, which is a mechanism to avoid a man’s investing in offspring other than his own (Daly, Wilson, and Weghorst 1982); and the mother-infant bond, which is probably a complex of adaptations both in mothers and in infants (Freeman 1974; Konner 1982; Stern 1977). Without denying that cultural conceptions of kinship always or often include more than the matters just discussed, kinship has its universal core in these highly specific mechanisms. And although it goes beyond kinship, the subject of the next section, reciprocity, is an aspect of phylogenetic adaptation that also lies near the core of kinship.
Reciprocity
Another solution to the puzzle entailed by the evolution of altruism is the idea of “reciprocal altruism” (Trivers 1971). An altruistic behavior that is reciprocated has its cost canceled and hence does not pose a serious evolutionary dilemma. But in order for this kind of behavior to prevail—to be more than neutral in its consequences—it must have some benefit for its practitioners. Insofar as reciprocated behaviors create coalitions of reciprocators, who may by virtue of their coalition prevail over those who do not reciprocate, then reciprocity should be selected. As is true of kin selection, the idea of reciprocal altruism rings bells in the minds of at least some anthropologists, since reciprocity has long been recognized as a universal cornerstone of morality, rational action, and group life—and has therefore been central to some of the most famous studies in the whole of anthropology (most are reviewed in Gouldner 1960). The strong moral feeling attached to reciprocity, and the assiduousness with which reciprocal action and reaction are watched also suggest some degree of innateness. The solidarity of kinsmen typically rests on both nepotism and reciprocity.
Sex differences in Sexuality, Aggressiveness, and Dominance
In the understanding of sex differences great strides have been made in the last decade or two. Some of the differences quite clearly are themselves adaptations brought about by sexual selection. A key element in the modern understanding of sexual selection is “parental investment” (Trivers 1972): the total energy or other resources a parent invests in an offspring (which limits what can be contributed to other offspring). Parental investment is related to sexual selection by the observation that whichever sex typically invests the most in its offspring will be a limited resource from the viewpoint of the sex investing less. For example, in a species in which the female devotes considerable time to rearing offspring, and the male no time beyond that re
quired to inseminate the female, from the viewpoint of reproduction there is in effect no shortage of males (the reproductive demands on their time being so minimal)8 while females (tied up as they are by lengthy gestation and offspring care) are in relatively short supply. A female who wanted to maximize her reproduction would gain little by having more males to inseminate her, but a male with the same aim would benefit by trying to monopolize access to females.
The sex that invests more in offspring is a “limiting” resource; it is the sexual resource that limits reproductive rates. The sex with the lesser investment tends to be larger and/or more colorful, to compete more actively with its fellows for access to the limiting sex, and to seek monopoly of multiple mates. The sex with the greater parental investment tends to rely more on choosiness (rather than active competition) in mate selection. Other factors being equal, the greater the sex difference in parental investment, the greater the other differences between the sexes, i.e., the greater the sexual dimorphism.
In mammals it is almost always the male that invests less, is larger, is more actively competitive, and is more prone to seek multiple mates. This pattern presumably results, in the long evolutionary perspective, from the typical difference in reproductive cells—the ovum is vastly more costly to the female than a sperm is to a male. This initial difference in parental investment biases the sexes of numerous species toward different reproductive strategies. Moreover, the mammalian pattern of internal gestation and postpartum lactation further enhances the female investment in offspring.9
These insights into the dynamics of sexual selection are directly applicable to humans. Humans are mildly dimorphic, their mating patterns are mildly polygynous, and the parental investments of humans seem to differ in the expected direction. The minimal investments (gestation and lactation versus insemination) are grossly different, but precisely what the typical investments may be is a matter of current research interest. Data from Aka Pygmies, who make a near approach to egalitarianism sexually and otherwise, show that mothers make a considerably larger direct investment in child care than do fathers—even though Aka males make unusually large parental investments (Hewlett 1988).
Human Universals Page 16
