Homicide

Foundations of Human Behavior

Martin Daly, Margo Wilson

• Publisher: Routledge
• Year: 2017
• ISBN:
  9781351515252
• Edition: 1
• Topic: Social Sciences
• Subtopic: Criminology
• Index: Social Sciences

The human race spends a disproportionate amount of attention, money, and expertise in solving, trying, and reporting homicides, as compared to other social problems. The public avidly consumes accounts of real-life homicide cases, and murder fiction is more popular still. Nevertheless, we have only the most rudimentary scientific understanding of who is likely to kill whom and why. Martin Daly and Margo Wilson apply contemporary evolutionary theory to analysis of human motives and perceptions of self-interest, considering where and why individual interests conflict, using well-documented murder cases. This book attempts to understand normal social motives in murder as products of the process of evolution by natural selection. They note that the implications for psychology are many and profound, touching on such matters as parental affection and rejection, sibling rivalry, sex differences in interests and inclinations, social comparison and achievement motives, our sense of justice, lifespan developmental changes in attitudes, and the phenomenology of the self. This is the first volume of its kind to analyze homicides in the light of a theory of interpersonal conflict. Before this study, no one had compared an observed distribution of victim-killer relationships to "expected" distribution, nor asked about the patterns of killer-victim age disparities in familial killings. This evolutionary psychological approach affords a deeper view and understanding of homicidal violence.

Homicide and Human Nature
−1−

Why do people kill one another? Many previous writers have hoped to illuminate the murky subject of human violence by theorizing about human nature. Their theories seem to have been more successful at provoking hostility than explaining it. Thinkers from St. Paul to Konrad Lorenz have been taken to task, with considerable justice, for misanthropic moralizing, for logical circularity, and for defending the interests of the privileged. We think the conceptual tools are available to do a better job.

The very distastefulness of violence obstructs objective analysis by inspiring “explanations” that are really just value judgments. Readiness to resort to violence, for example, is regularly interpreted as “primitive” or “immature.” Each of these labels seems at first to imply a coherent theory of the origins of violence. Yet even if one accepts, for the sake of argument, the dubious concept of “primitiveness,” there turns out to be no empirical support for the assertion that violence is more characteristic of the “primitive”—whether cultures, species or whatever—than of more “advanced” forms. As for “immaturity,” potentially lethal violence—in Homo sapiens as in most familiar creatures—is the virtually exclusive province of adults, not juveniles, and there is not a shred of evidence that violent people are the products of some sort of developmental arrest. These labels masquerade as theories, although they are really little more than facile disparagements. They reveal more about the prejudices of their proponents than about the causes of violence, and they are worse than no theories at all.

The manifest inadequacy of such simplistic explanations has led most scientific students of violence to shy away from general theories. Why do people kill one another? A hundred answers spring to mind, each limited in its domain but tractable to investigation. Because violent people were themselves abused in childhood. Because of envy engendered by social inequities. Because the penalties are not severe enough. Because of brain tumors, hormone imbalances, and alcohol-induced psychoses. Because modern weapons bypass our natural face-to-face inhibitions and empathies. Because of the violence on TV.

Every one of these answers can be used to generate testable hypotheses. Thus, some investigators compare convicted killers with nonviolent control groups, seeking objectively measurable differences in physiology or personality or upbringing. Others predict that particular cultural or demographic measures will be associated with differential rates of violence in comparisons among nations or cities. Research proliferates. The researchers stake out careers as the leading advocates of one or another hypothesis or “model.” And indeed, there is evidently some truth to all of them, for they are seldom formulated as alternatives. Any of the above hypotheses, for example, might be supported or refuted by empirical test and we would remain none the wiser about the validity of the others. One answer tries to characterize the emotions motivating homicidal action; another addresses developmental antecedents. One theorist explains human action in terms of anticipated rewards and punishments, while another invokes androgens or endorphins. Each addresses one small part of what we want to know when we ask “why.”

We believe that there is still a place—indeed, a need—for a more encompassing perspective, one that will account for violence within the framework of a well-founded general theory of human nature. We believe, moreover, that the basis for such a theory of human nature is already available in an existing general theory of the nature of all life. This general theory was first proposed well over a hundred years ago and is today about as legitimately controversial as, say, the atomic theory (still, after all, “just a theory” of the nature of matter). In other words, we know with as much certainty as science knows anything that the theory in question is basically correct. It is the bedrock of all life sciences from molecular biology to community ecology, and yet its relevance to the social sciences remains shamefully unappreciated. We refer, of course, to Darwin’s theory of evolution by natural selection.

A Brief Introduction to “Selection Thinking”

Organisms are complex adaptive systems. How can such order have come into being? Only two coherent answers have been proposed, and only one turns out to be worth considering. The older theory is that organisms are adaptively constructed because someone made them that way. This is an enormously popular theory which has been invented many times in many lands, but it is scientifically worthless. The problem with creationism as a scientific theory is not its transparent anthropomorphism, nor even that its advocates always seem sure which one of the numerous creation stories is the true one. The more serious problem is that creationism is simply devoid of empirical implications. Whatever turns up must be the will of the creator(s). Implications for the practical investigation of the natural world are nil.

The adaptive construction of organisms once constituted the most powerful argument for the existence of god(s). Charles Darwin and Alfred Russel Wallace destroyed that argument in 1858, when they described a natural process that creates adaptation automatically. Darwin called it “natural selection.” According to Darwin and Wallace, adaptation arises because the continual generation of random variation is continually followed by differential survival and proliferation that is nonrandom, the more adaptive forms persisting while their alternatives perish. This is a theory with endless implications about what we are likely to encounter in the natural world, and about how we should go about investigating it. If anyone has come up with a third alternative to explain why organisms are adaptively constructed, it has not been made generally known.

When we say that organisms are complex adaptive systems, we mean that their attributes appear to have been shaped to their purposes. This is perhaps clearest with respect to morphology. We find a fossil jaw full of molars, which are evidently grinding teeth, and we infer that an extinct creature with such teeth must have partaken of grindables. We are reasonably confident that particular tooth structures served particular functions, partly from observation of the diets of living creatures, but also partly from considerations of efficient “design”: Molars aren’t built to puncture and saber-teeth are not built to grind grain.

If we are good scientists, we do not merely infer the uses of some structure and sit back satisfied. Rather, we treat such inferences as hypotheses, and we try to derive further implications that will subject these hypotheses to potential disconfirmation. We predict, for example, that an apparent grinding tooth will articulate in a certain way with another; we predict muscle attachments appropriate to the hypothesized grinding action; we predict certain patterns of wear. And as each predicted detail—improbable under competing hypotheses—is confirmed, we become increasingly confident that we have attributed the correct adaptive function to the tooth. This sort of attempt to identify the functions of the various attributes of an organism is lately referred to by the ugly label “adaptationism.”

The adaptationist approach is just as applicable to living creatures as to extinct ones, and just as applicable to dynamic physiological characteristics as to static morphological ones. The heart, we say, is a pump, and the movement of fluid is its function. Eyes are organs for seeing, and the adjustable lens and iris are precisely what is needed for resolving images under variable conditions. The evidence that these functions are indeed correctly identified is diverse, but the most essential point is evident design for the function in question (Williams, 1966). The lens must be transparent, the retinal cells must be photoexcitable, and many other improbable things must be true if the eye is going to see. Those who study organismic adaptations are so regularly confronted by the power of natural selection, that apparent failures of design seem themselves to demand explanation in adaptationist terms. Were the heart, for example, a terribly inefficient pump which could be improved by some change in its proportions, we should probably be justified in doubting that its primary function is pumping and in hypothesizing that its efficiency as a pump is compromised by the contrary demands of another function, as yet unknown.

It may not at first be obvious just what purpose some structure or physiological process serves. Various hypothetical functions, including cognition, were attributed to the heart before its role in circulating the blood was understood. But progress in understanding has generally followed from the scientist’s assuming that the structure under study has some utility for its possessor, and attempting to establish what that utility might be. This is an important point because the adaptationist program has recently been criticized from within evolutionary biology, and while the critique has merit, it has been overstated. Palaeontologist Stephen Jay Gould and population geneticist Richard Lewontin have been the main critics of adapta tionism. Their pet example is the human chin, and it will suffice to make their point. Our chin is a peculiar structure among the primates, and one might wonder what good it is. Gould and Lewontin (1979) assert that the chin is itself functionless, but can be understood as the epiphenomenal byproduct of other naturally selected changes in growth and structure. Whether they are right in this particular case or not, the general point is well taken: One may indeed slice the pie the wrong way, abstract out meaningless traits, and waste much effort in blind alleys. But what is one to conclude? That Harvey should not have wondered what hearts are for? The caveat is useful, but it is hardly a general indictment of adaptationism; as Ernst Mayr (1983) has noted in response to Gould and Lewontin, essentially all the major advances in biological research have been predicated upon the assumption of adaptive function.

In the study of behavior, as in morphology and physiology, researchers assume that the properties of organisms are adaptively constructed as a result of selection, and inquire how behavior is organized to serve the interests of the actors. Predators, for example, exhibit search strategies adapted to the dispersion of their prey, searching the vicinity of the last capture if the prey species is a gregarious one, but moving on if it is solitary (e.g., Smith, 1974). Small mammals that are usually timid become fierce when they have pups to defend (e.g., Svare, 1981). A behavior pattern of unknown utility presents a puzzle to the researcher, who tries to formulate and test hypotheses that would explain why the animal should act thus and not otherwise.

Herbert Spencer epitomized the theory of natural selection as “survival of the fittest.” Wallace and Darwin thought the phrase to be apt (see Dawkins, 1982, pp. 179-180), but it has produced a lot of misunderstanding, because both “survival” and “fittest” turn out to mean something other than one might at first imagine. When we speak of the “survival value” of adaptive characteristics, we naturally think of those devices that help the individual find food, conserve energy, dodge predators, and fend off disease. But personal survival is not the bottom line on the natural selective ledger. Over generations, it is successful traits that “survive,” not individuals, and this sort of long-term survival depends not only or even primarily upon the longevity of those carrying the trait, but upon the abundance of their progeny. Should a more aggressive type of male appear in a population of long-lived pacifists, for example, and should the new type tend to fertilize more females but die younger than the old, then that new type will supplant the old by natural selection, and male life span will decline. It is reproductive success, not bodily condition, that the evolutionist refers to as “fitness.”

It is commonly asserted that people and other creatures look to their survival needs first, and that only when these are satisfied do they turn to the gratification of sexual and other “inessential” drives. Many observations seem to affirm such a hierarchy of needs, and it is easy to see why that should be so. Death terminates one’s capacity to promote one’s fitness; if inclinations have been shaped by natural selection, life should almost always be preferred to death. In other words, life is valued because of its historical contribution to fitness, and not as an end in itself. Without this insight, we cannot understand why animals ever take risks. A stickleback fish guarding a nest full of eggs, for example, will stand his ground against an approaching predator longer and dart at the predator more bravely, the more eggs he has in the nest (Pressley, 1981). In effect, the greater fitness value of a larger brood elevates the statistical probability of death that the little fish is prepared to incur. What “selection thinking” suggests is that the evolved motivational mechanisms of all creatures, including ourselves, have been designed to expend the organism’s very life in the pursuit of genetic posterity.

Evolutionary Psychology

A Darwinian view of life suggests that the ultimate currency of adaptation is expected fitness. But fitness is a distal end, and we can often analyze the adaptive logic of behavioral control mechanisms quite thoroughly in terms of more proximal goals. Efficiency in gathering food, for example, is obviously useful both for staying alive and for building babies. A student of the adaptive organization of foraging decisions might therefore ignore fitness altogether, and simply test whether the forager acts as if to maximize the number of grams of protein collected per hour or the number of calories ingested per unit of predation risk incurred.

Physiologists and psychologists routinely assume efficient design when they study thirst or respiration or the processing of sensory information, and yet they rarely give a thought to the details of the natural selective process that has sculpted their subject matter. For the most part, this neglect of the natural selective process really does not matter (Symons, 1987). The question of what would be an effective design for an image-analyzing organ, for example, is unaffected by the question of whether the organism’s ultimate goal is fitness, survival, or beatitude. However, the concept of the organism as a mere “survival machine” does not always work; sometimes we have to consider the animal’s traits as means to the end of genetic posterity in order to understand them. When fathers are seen to evaluate risks differently from bachelors, for example, or mothers are seen to sacrifice their skeletal calcium to maintain their milk quality—when one treats relatives differently from strangers, or age-mates differently from elders—then selection thinking becomes essential if we are ever going to make sense of the actors’ motives.

Our theoretical approach in this book is to use Darwin’s discovery that the properties of organisms have been shaped by a history of selection as an heuristic for the generation of models and hypotheses about the sorts of psychological mechanisms that an animal like Homo sapiens might be expected to have evolved. We then use these psychological models and hypotheses to predict and explain patterned variation in the risk of interpersonal conflict and homicide. What to call the paradigm within which we are working is slightly problematic. Symons (1987) refers to it as “Darwinian psychology,” but in our experience the use of this term (and of “Darwinism”) sidetracks many readers into fruitless discussion of what Darwin himself did or did not believe. Tooby and Cosmides (1988) use the term “evolutionary psychology” and so shall we, although it can mislead by seeming to imply explicit phylogenetic reconstruction; consider the phrase a shorthand for “psychological theorizing informed by modern evolutionary theory.” We shall also use Charnov’s (1982) phrase “selection thinking,” awkward, perhaps, but refreshingly lacking in distracting connotations. Terminology aside, the important point is this: We are not trying to “test Darwinian theory,” but rather to use modern evolutionary ideas to generate new ideas about human social psychology and behavior. The proposition that the human psyche has been shaped by a history of selection cannot reasonably be doubted, but just what this proposition implies has barely begun to be explored.

Evolutionary psychology is not a theory of motivation. No one imagines that genetic posterity (fitness) is a superordinate “goal” in any direct sense. Fitness plays a quite different role in evolutionary theory from the role that self-esteem or a target level of blood glucose plays in a psychological theory. Fitness consequences are invoked not as goals in themselves, but rather to explain why certain goals have come to control behavior at all, and why they are calibrated in one particular way rather than another. This distinction between fitness consequences and proximal objectives is consistently misunderstood by those social scientists who point to vasectomies or adoptions as evidence against selectionist models. Selection shapes the minds and bodies of organisms to the particular conditions within which selection has been operating. Adaptation is not prospective. The apparent purpose in organismic design depends upon the persistence of essential features of historical environments.

The concept of natural selection explains behavior at a distinct level complementary to the explanations afforded by motivational theories. A psychologist might be satisfied to explain the behavior of two men fighting a duel in terms of self-esteem or status or face. An evolutionary psychologist will also want to clarify why the human psyche should be such as to value intangible social resources enough to risk death over them. For although psychology typically focuses upon a different level of explanation from that offered by evolutionary theory, it does not follow that motivational theorists can safely ignore evolutionary biology. Had Freud, for example, better understood Darwin’s theory, we might all have been spared his fruitless postulation of the death instinct. Many other theories that are still debated by social scientists implicitly deny the action of natural selection, and are therefore surely wrong. Moreover, what Symons (1987) calls an “imagination informed by Darwinism” is likely to arrive at productive motivational hypotheses that would not otherwise arise. Selection thinking leads us, for example, to a set of detailed predictions about variations in the strength of maternal love as a function of the mother’s age, the child’s age and several other variables, and there is impressive evidence, as we shall see in Chapters 3 and 4, that this theory of maternal motivation, inspired by evolutionary theory, is correct.

Several critics of “sociobiology” have complained that the application of selection thinking to the explanation of behavior is inappropriately “deterministic.” This accusation is philosophically naive. If it is indeed meaningful to complain about “determinism,” then the charge must be leveled against all scientific approaches to the study of behavior. Biologist and sociologist alike are committed to the belief that the phenomena under study have knowable causes. We chip away at “unexplained variance” within our various paradigms, trying to better understand what makes the creatures we study do what they do. The entire enterprise is predicated upon “determinism.” As our science progresses, we may become concerned about its implications. How, for example, can we retain our belief in free will and personal responsibility as our knowledge and predictive powers grow? But if this is indeed a dilemma, then it is a dilemma for us all. Consider, for example, the writings of the leading behaviorist, B.F. Skinner. His insistence upon the paramount importance and unified nature of experiential learning is generally viewed as the antithesis of “biological determinism,” and yet Skinner’s faith in the power of reward and punishment compelled him (1971) to reject “freedom and dignity” as illusory. Those who accuse evolutionists of determinism commonly go on to attribute behavioral causation to social and economic factors; ironically, these are the most popular proximal causes in evolutionary theories too. Unfortunately, these critics do not explain how their preferred theories are able to impute causality and yet avoid determinism.

Although “determinism” is a phony issue, there is a genuine disagreement between “imaginations informed by Darwinism” and those social sci...