"The course of true love never did run smooth," as Shakespeare noted. Although directed to romantic love, the observation also applies to parents and their offspring—which appears counter to basic evolutionary wisdom. After all, the biological interests of parents and children would seem to coincide perfectly, because the latter are the former's major route to evolutionary success. The two generations ought, therefore, to be on the same page, because successful children literally mean successful parental genes. (Indeed, success in projecting those genes into the future is the only biological reason to reproduce in the first place.)
Years of Walt Disney True Life Adventures, combined with cartoon images from Dumbo to Bambi, Lady and the Tramp, and One Hundred and One Dalmatians, have reflected, as well as generated, the expectation that animal parent and child—especially mother and child—are the epitome of shared goals and perfect amiability. The image among human beings is, if anything, even more clearly established: Madonna and Child convey a sense of peace and contentment that transcends the merely theological.
When rough spots emerge in the parent-child nexus, the traditional view among psychiatrists, psychologists, and sociologists—like Talcott Parsons or Jerome Kagan—has long been that the culprit is simply misunderstanding, with its attendant failures of communication. Everyone means well. It's just that in the course of conveying heartfelt parental assistance, advice, protection, nurturance, and information to the child, sometimes there are problems, largely because the child—being young—is necessarily inexperienced, perhaps occasionally a bit headstrong, and generally uninformed as to his or her true interests. The more mature child gradually recognizes that it is best to go along with parental inclinations, at which point, conflict ceases and "socialization" has been achieved. Thus parent-offspring conflict is largely due to the fact that children are primitive, even barbaric little creatures, who need time to become responsible adults.
Then there is the psychoanalytic tradition, which focuses on sexual rivalry, especially among fathers and sons. As a result of presumed Oedipal conflict, boys are terrified that their fathers will castrate them; girls, for their part, resent not having a penis, and so all hell breaks loose until, in time, things quiet down and children reconcile their innate sexual conflicts with their social roles.
Contrary to what you might expect, the view from evolutionary biology is quite different, rather darker, and much more persuasive.
We owe it almost entirely to work by Robert L. Trivers, currently a professor of biology and anthropology at Rutgers University in New Brunswick, N.J., and undoubtedly our most creative living evolutionary theorist. These days, evolutionary thinking has permeated not just biological and (increasingly) social science, but popular culture as well. Surprisingly, however, Trivers' theory of why evolution creates intergenerational conflict, which has major implications for family dynamics, has largely been ignored by developmental psychologists and family sociologists.
In a landmark essay published in 1974, "Parent-Offspring Conflict," Trivers emphasized that although parents and offspring do have a substantial shared genetic interest, that overlap is not complete, based as it is on a 50-percent probability that any gene present in a parent is also present in the child. Insofar as the child succeeds, the parent does, too. Or at least, one-half of the parent. But just as there are two sides to every story, there is also the other half when it comes to each offspring's genetic makeup. In every biological parent-and-child pair, precisely one-half the genes of each are not shared. Previous observers have focused on the glass half-full—the convergent part of genetic identity, ignoring the other, empty half.
Not only that, but biologists—and most psychologists, psychiatrists, and sociologists to an even greater extent—have treated the child as an appendage to the parent, rather than a separate being with distinctive strengths and weaknesses, and, more important, an agenda of his or her own.
Trivers suggested that we consider a newborn infant, say, an elephant calf. Initially the interests of infant and mother coincide: The calf needs various things from its mother, milk in particular. And the mother is prepared, even eager, to meet those needs. In the short term, her hormones as well as her anatomy predispose her to lactate. But then something happens. The infant grows older, larger, and less dependent on her milk. At the same time, she becomes inclined to discontinue nursing. After all, milk is energetically costly to produce, and at some point, she will do better in terms of her own fitness if she stops investing in this child and prepares to put precious resources into another. (In many mammals, lactating females are inhibited from ovulating, so the nourishing of one offspring precludes making another.) In itself, this need not lead to conflict—if the infant agrees with the mother. Unfortunately, that usually doesn't happen.
The mother, we must recall, is ultimately selected ("naturally") to make the most of her fitness, not necessarily that of her offspring. In fact, her only reason for creating that offspring in the first place is as a means of advancing her own evolutionary fitness. By the same argument, the infant is ultimately interested in making the most of his fitness, not his mother's. More precisely, the infants are only 50-percent related to their mothers but 100 percent related to themselvesitself. (And vice versa for the mothers.) As a result, the infant devalues his or herits mother's interests by a factor of one-half, which the mother reciprocates: That is, mother and infant are each only one-half invested in the other's success, or—by the same token—only one-half as averse to the other's costs.
Think of the therapist's cliché, "I can really feel your pain." Infant and mother can each only feel one-half of the other's pain.
The upshot is that after a period in which mother and infant are in agreement about nursing, a predictable zone of conflict arises. The mother and infant become locked in a battle of evolutionary wills, with the infant selected to demand more than the mother is selected to give. But there is light at the end of this tunnel. For the mother, the cost of nursing continues to mount, while for the infant, the benefit of nursing begins to decline. Eventually it becomes in the infant's interest for the mother to stop giving so much and to start taking care of herself—or, another way to see it, the infant wants the mother to provide siblings, so as to enhance the biological fitness. The mother is only too happy to oblige (in order to maximize her own), and nursing is finally discontinued.
Weaning conflict is widespread in nature. Observe a cat with kittens: The mother initiates most of the early nursing bouts, until the young are around 3 weeks. For the next 10 days or so, the kittens and their mother are equally likely to initiate nursing. By about Day 30, however, it is the kittens who attempt to nurse, while their mother discourages their efforts, to the point that she is likely to get up and leave.
Something similar even takes place among birds. Large nestlings—big enough to fly, hence known as fledglings—can often be found pursuing their harried parents, importuning them for food. Throughout North America in late spring, it is common to see fledglings quivering their wings and uttering incessant "begging" calls, while the parents back away, look far into the distance (as though trying to ignore what is in front of them), and often literally take wing, pursued by their nearly grown but indefatigably demanding offspring. One of the most comical examples is the so-called "feeding chase" of flightless Adélie penguins, in which the adults waddle about all over the rookery, desperately pursued by rapacious juveniles.
More generally, the conflict is over what Trivers in an earlier study had termed "parental investment"—the various expenditures of time, energy, resources, and risk that parents make in their efforts to care for their offspring. It is not hard to draw parallels to people. In fact, it is hard not to do so.
In our own species, parent-offspring conflict is variable, but it probably goes on longer and is more intense than in any other creature. Many a harried parent, struggling to provide for even the most rewarding and undemanding child, will answer the question, "What do you want your child to be?" with an immediate reply, "Self-supporting!"
Then there is the question of college. Some parents pay for it willingly; others only grudgingly. Yet others, not at all. Clearly, as offspring grow older, some sort of transition is reached, although most of the time, children would appreciate more parental investment (albeit less meddling) than parents are inclined to provide.
The joke goes as follows: Son writes to Father, after a few months at college: "Dear Dad, No mon, no fun, your son." Father responds to Son: "Dear Son, Too bad, so sad, your dad." I would bet a similar dialogue obtains cross-culturally.
The implications of the theory of parent-offspring conflict are profound, with much yet to be explored. Trivers points out, for example, that conflict can be expected not only over the timing of the withdrawal of parental investment, but also over the amount provided. How much, for example, is a parent predicted to invest in a given offspring at a given time? Answer: until the parent's benefit exceeds his or her cost. Offspring, however, can be expected to see things differently, because each one devalues parental cost by a factor of one-half. The result: conflict once again.
Parents and offspring can also be expected to disagree in predictable ways regarding behavior toward a third party. Consider two siblings. Given the probabilities of genetic relatedness, all other things being equal, we expect one sibling to help another (be "altruistic") whenever the cost to the altruist is less than one-half the benefit derived by the recipient. Parents, however, can be expected to encourage altruism whenever the recipient's benefit exceeds the donor's cost, because parents are equally related to each of their offspring. The result is yet another predicted zone of conflict, with parents anticipated to urge their children to share and play more nicely (in fact, twice as nicely!) as the children are themselves inclined.
Think, as well, about cousins. Given double the probability of sharing genes with a niece or nephew than cousins have with each other, a parent is likely to urge offspring to be more involved with their cousins (nieces or nephews of the parents) than the offspring themselves are inclined.
How will the various predicted patterns of parent-offspring conflict be resolved? Here, too, Trivers has made some provocative suggestions. He notes, for example, that given the physical mismatch between nursing mother and infant, the latter can hardly be expected to fling the former to the ground and demand more milk than she is prepared to provide. On the other hand, offspring are not without options, particularly psychological ones. Despite anticipated conflicts, parents and offspring undoubtedly have a fundamental shared interest in the latter's success, and offspring are far better positioned to know their own degree of need. As a result, they can be expected to employ numerous psychological tactics (crying, smiling, depending on circumstance and opportunity) to get their way, although they would be ill-advised to avoid grossly overrepresenting their neediness, lest parents give up on them entirely. At the same time, while they might want to emphasize their competence and potential, thereby making themselves appear to be good evolutionary investments, they don't want to appear too good, lest they be deemed capable of flourishing on their own.
For their part, parents can be expected to distinguish—or at least, attempt to distinguish—proclaimed need from the real thing. They're well advised to refrain from being evolutionary suckers, excessively manipulated by their offspring, yet at the same time, any genetic tendency on the part of parents to be indifferent to their offspring's genuine requirements would be strenuously selected against.
As to the self-presentation of parents, Trivers points out that it shouldn't be beyond the adaptive ingenuity of evolution to have outfitted them with a predisposition to play up their own wisdom and beneficence. After all, just as offspring genuinely have valuable information (about their own condition) not directly available to their parents, parents have not only resources but also information (about the nature of the world) that is truly useful to their offspring. Hence, parents can be expected to point to that presumed and, in most cases, genuine store of wisdom—but also, if anything, to exaggerate its worth, proclaiming that father (or mother) knows best.
The reigning paradigm in developmental psychology continues to be adult-centric. That's not surprising, insofar as it is developed and promulgated by adults. An evolutionary perspective emphasizes that the parent's viewpoint, almost by necessity, would give offspring short shrift, although they are independent agents, motivated by considerations that are no less valid and often opposed to those of parents. It is challenging to predict how developmental psychology, child psychiatry, and family sociology would be reconstituted if and when those fields were reformulated to incorporate the evolutionary theory of parent-offspring conflict. But it is safe to predict that they would be considerably different from the present. And that we would have far more insight into teenage rebellion and possibly postpartum depression, for example, than we do today.
Evolutionary biologists familiar with the theory of parent-offspring conflict are not surprised that the dominant ideology—both in social science and in normal family life—tends to privilege adult wisdom and good intentions over juvenile "intransigence" and "ignorance," despite the children's "self-esteem" movement and periodic emphasis on youngsters as independent actors in their own right. A truly biological perspective, by contrast, suggests that the interests of neither parents nor offspring should be considered determinative; rather, they are interactive, dynamically interpenetrating and, on occasion, diametrically opposed. In such cases, the likely results are evolutionary arms races, tugs of war, and various manifestations of outright conflict, often with no obvious victor. For beleaguered parents and their offspring alike, this may not constitute surprising news, but for supposed experts whose "expertise" may well have been based on a thoroughly inaccurate and nonevolutionary view of their subjects, the theory of parent-offspring conflict promises—or threatens—to produce a new and(r)evolutionary paradigm.