behavioral ecology “sociobiology,” h...

BEHAVIORAL

ECOLOGY,“SOCIOBIOLOGY,”

AND HUMAN

BEHAVIOR

Bobbi S. Low

Research TOC

When Juliet was twelve, her father, without consulting her,betrothed her to a man more than twice her age. She,being in love with Romeo, complained. Her father’s

answer was (Act III, Scene V):

An you will not wed, I’ll pardon you!Graze where you will, you shall not house with me; …An you be mine, I’ll give you to my friend;An you be not, hang, beg, starve, die in the streets,For, by my soul, I’ll ne’er acknowledge thee,Nor what is mine shall never do thee good.

Today, in the United States, Juliet would probably sue her fatherfor child abuse. And she would be likely to win. What is common,approved, and thought ethical varies widely across human cul-tures in time and space: whether one may marry more than oneperson at a time; who chooses marriage partners; whether abortionand infanticide are approved or forbidden; whether one may eat allmeats, some meats, or none; what kinds of killings are forbidden orencouraged. How are we to make sense of all this variety?

Human behavior has traditionally been the province of anthro-pology, sociology, and psychology. Within each of these fieldsthere exist diverse approaches. Recently, behavioral ecology, anevolutionary approach to why we behave as we do, has joinedother fields in trying to explain some of the diversity in humanbehavior. With its roots in Charles Darwin’s work1 on naturalselection, it examines how environmental conditions influence liv-ing things. Human behavioral ecology is one of a variety of quitesimilar evolutionary approaches to human behavior, with a varietyof names: evolutionary ecology, biosocial science, human ethology,sociobiology, socioecology, evolutionary biological anthropology,and others.2 Depending on who is reporting, these may vary sub-tly, or be different names for the same thing.

When E. O. Wilson first published his book Sociobiology hedefined the subject as “the systematic study of the biological causesof behavior.”3 His definition may have seemed relatively straight-forward at the time; however, much controversy has arisen sincethen, perhaps because Wilson did not define what he meant by“biology.” Today some writers use (or accuse others of using) theterm to mean “genetic determination of traits, independent of envi-ronmental variation.” In fact, no one really uses such a definition.4

When we want to study why we act as we do, in an evolutionaryframework, we begin by acknowledging that environments, genes,and history interact to influence behavior.

Human behavioral ecology focuses on how much of humanbehavior we can understand and predict, by using the same logic

3

and principles we use to analyze behavior in other species. Ofcourse we don’t expect to be able to predict all of human behavior.Human behavioral ecology begins, at least for the purposes of gen-erating hypotheses, by using the central paradigm in biology:Humans, like other living organisms, have evolved to maximize theirgenetic contribution to future generations through producing offspringand assisting nondescendant relatives; the particular strategies accom-plishing such maximization will differ in specific ways in different envi-ronments, and, just as for other mammals, these strategies will typicallydiffer between the sexes.

Behavior is assumed to be the product of the interaction ofgenes and environment—not the result purely of genetics or envi-ronment. Behavioral ecology asks when and how environmentalconditions (including social conditions) change individuals’genetic costs and benefits, and therefore predict the kinds ofbehavior we are likely to see. The propositions underlying this par-adigm include the following:

1. Organisms are generally well suited to the environments inwhich they live; they achieve success in any environment by getting resources that help them survive and reproduce (get genes into the next generation).

2. Variation exists in how well organisms do this. Only heri-table (correlated between parents and children) variation isappropriately considered, for only this accumulates overtime. a. An individual organism can help its genes to spread by

reproducing directly, by assisting individual organisms carrying copies “identical by descent” (IBD) of its genes (kin selection), or, under certain circumstances, by helping individual organisms that do not carry IBD copies of its genes, if such assistance is returned in genetically effective ways (reciprocity).

b. The genes of individual organisms that help reproductive competitors without any reciprocation willtend to disappear from existing lineages.

3. In the evolutionary history of all species, there have beenimportant proximate correlates of reproductive success,including resource control (food, territory), rank (status,power, or wealth), and, in highly social species such ashumans, social “reputation.” However, no organisms,including humans, have evolved to perceive or assessdirectly the spread of genes. Instead, organisms behave asthough these proximate correlates were their goals.Because environments change, species may find them-selves in novel evolutionary environments, and theirbehavior may be currently maladaptive.

4 RESEARCH FRONTIERS

4. Humans are not qualitatively different from other livingorganisms. Like other living things, they evolved to getand use resources to survive and enhance the spread oftheir genes. To behavioral ecologists, this is parallel toarguing that humans, for example, while they can makeairplanes fly, are still subject to the laws of gravity.

I will explore examples both of the controversies concerningthis novel approach and of how such an approach can be used tocomplement other knowledge. Controversy arises over severalissues. Some of the propositions taken to be true here are simplynot accepted by everyone; for example, not everyone thinks thathumans are sufficiently like other species to allow us to generalizefrom propositions well understood in other species to humanbehavior, even to allow us to test hypotheses. Some feel that we arepsychologically unique, and we should not analyze certain aspectsof ourselves. These concerns seem to me more a problem of com-munication than of science. The tests are relatively straightforward;one can make the assumptions that generate the predictions, andthen see whether they are upheld or falsified.5

But there are more interesting controversies surrounding anevolutionary approach. So much heat was generated by the earlyfights over E. O. Wilson’s work that real misunderstandingsremain. Two of the most common are (1) if genetic representationis the important criterion, anything less than maximum physiologi-cally possible reproduction must represent an individual sacrificeor an evolutionary mistake; and (2) explanations that focus on theparticular stimulus for a behavior (proximate cause) are in conflictwith explanations that focus on predicting the evolutionary condi-tions under which such behavior will be genetically profitable (ulti-mate cause). Neither of these conceptions is true.6 These misunder-standings are so widespread, and so unnecessary, that I willexplore them in more detail later.

Finally, there are controversies within the field generated bypoor work and poor communication. For example, a recent studyproposed that there are racial differences in law-abidingness, sexu-ality, and intelligence.7 Careful examination of the work shows thatthe traits considered (such as “law-abidingness,” defined as arrestrates) are meaningless because they are closely correlated withother factors (socioeconomic status, racial prejudice). Some of the“racial” groups are defined in unique ways; the results would bedifferent if different definitions were used. Not only the results butalso the definitions of race and the traits studied are controversial.Still, the obvious solution is the usual one in scientific debates:

5HUMAN BEHAVIORAL ECOLOGY

challenge and test. Good science should drive out bad science,even on highly-charged topics.

WHAT CAN A BEHAVIORAL

ECOLOGICAL PERSPECTIVE ADD? Several new perspectives mark behavioral ecological approaches.First is the importance of using repeatable observations in wayssimilar to other sciences: primarily, optimality modeling (seekingto model and test optimality of behavior—for example, in a givenenvironment, which strategy is most effective?), and the compara-tive method (using existing variation as a “natural experiment” totest hypotheses).8 Most novel, when we think of human behavior,is the idea that genes themselves are a sort of currency to be maxi-mized, and that by understanding the impact of particular behav-iors in specific environments on gene frequencies (or on their prox-imate correlates—things that vary with them—like status orhealth) we can make new, testable, and sometimes unexpected pre-dictions. It follows from this approach that individual reproductiveinterests can lead to group-wide patterns—in stark contrast to theolder idea that we do things for the good of the group. Thisapproach can often make sense of previously puzzling patterns.

Behavioral ecology straddles traditional subfields in anthropol-ogy; it looks at behavior, like cultural anthropology, but does sousing principles derived from biology, like biological anthropology.It bridges fields as diverse as animal behavior and the decision sci-ences, like the rational-actor approach in economics. It incorporatesquantitative methods and techniques from many fields to analyzecomplex social behavior. Behavioral ecology has a strong traditionof scientific method, phrasing questions as testable hypotheses inorder to examine them with repeatable observations. Perhaps mostexciting, behavioral ecology leads us to ask new questions abouthuman behavior that might not have occurred to us before.

Behavioral ecology’s linking of behavior to environment—forall species—might surprise you, if you imagine that nonhumanspecies are too simple and stereotypic to be good models forhuman behavior. But other species’ behavior is often more com-plex than we might suspect, and can show us something of howgenes and environment interact. For example, optimal foraging the-ory postulates that foraging efficiency increases relative reproduc-


tive fitness. In ground squirrels, optimal foragers survive better andhave more babies than nonoptimal foragers. Optimality in foragingis heritable: Babies forage more like their parents than like others inthe population. However, heritability is only about 60 percentgenetic; the other 40 percent of the parent-offspring correlation inoptimality comes from babies foraging near their mother and learn-ing what to eat.9 Thus, there is intergenerational information trans-fer in ground squirrels. The functionally important facts are thatheritable variation exists; that one can predict, in a specific environ-ment, which strategies (learned as well as genetically transmitted)ought to result in increased reproductive fitness for their possessorsand in a larger proportion of the possessors in the population; andthat one can test and falsify these predictions.

Learning, then, is a form of intergenerational transmission (cul-tural heritability) that we humans have elevated to a high art, but itis not unique to us. Learning and/or cultural transmission areimportant, for example, in chimpanzees and other primates, groundsquirrels, birds, amphibians, fish, honeybees (in which differentindividuals, depending on their experience, learn to specialize onvarious flower species, thus becoming more efficient) and sweatbees (who learn to identify their kin in order to guard their nests).Learning appears to be important in complex and unpredictableenvironments. The evolutionary environment of humans had manyuncertainties, so it may come as no surprise that we evolved to bepremier learners and transmitters of learned behaviors.

ASKING BEHAVIORAL QUESTIONS

Consider ravens: They show a curious behavior. A small group ofravens, feasting on a dead moose, may give a distinctive, loud,high-pitched “yell.” Other ravens are attracted to the yelling; theresult is more ravens at the kill, and less food for the yellers. Whydoesn’t the raven who first finds a kill just keep quiet? The ravensseem to be sharing in a truly nonprofitable way. Yet behavioralecologists find true genetic altruism to be so rare as to be a fluke.The first question, of course, is whether the “called” birds arerelated to the callers—since sharing with individuals who carry atleast some of your genes can help spread your genes. After muchwork, Bernd Heinrich, the behavioral ecologist who found thisbehavior, eliminated that possibility.10 What else could be possible?

Beginning with the hypothesis that ravens are likely to act in


self-interested ways, Heinrich made a series of careful observations,comparing the behavior of different ravens under various circum-stances (similar to the comparative method of cross-culturalresearch). He found that adult ravens were territorial, controllingany carcasses in their territory and driving off any juveniles.Territorial adults never yelled when they found a carcass. However,when a juvenile found a carcass, it was likely to yell, attracting otherjuveniles; when enough juveniles were present, the resident territor-ial adults could not drive them off. Heinrich did not simply create a“just-so story”; he used careful hypothesis-making, observation, andtesting to discover what is, in fact, the most likely functional reasonfor the ravens’ behavior. If our goal is to understand, and (we hope)predict how human behavior might vary in different environments,we could profitably use similar careful approaches.

NATURAL SELECTION, KIN SELECTION,

AND RECIPROCITY

At the core of behavioral ecology rests the notion of the selfish gene:Genes that get themselves copied into more and more individualswill be the genes that prevail and persist through time.11 Genes, ofcourse, travel about in interactive groups (the genotype) inside indi-viduals, and individual strategies for survival and reproductionare all-important. It may be complicated to analyze; in fact, we sel-dom know the actual genetics of behavior in any species. We makesome simplifying assumptions: that there has been enough geneticvariation in the past for natural selection to operate, and that nat-ural selection does operate to mediate possible conflicting forces.Grafen calls this the phenotypic gambit.12

The selfish gene is a modern version of the simple logic firstemployed explicitly by Darwin, and given in the four propositionsstated earlier. The organisms we see today are the descendants ofthose that successfully survived and reproduced in past environ-ments. Genetically selfish behaviors, those that enhance an individ-ual’s genetic representation, are always favored. Seems simple—butcomplex, unexpected, and profound effects follow. For example,having the maximum number of babies is often not the route tohaving the maximum number of grandchildren—this is a wide-


spread misunderstanding. What matters is the effectiveness ofparental care in making offspring successful. If parents can protecttheir offspring from dying (which is expensive and likely to lowerfertility), successful parents may be those that produce fewer off-spring but raise more of them to adulthood. This is the crux ofreproductive strategies in other species, and crucial for humans.13

Behavioral ecology focuses on predicting behaviors that suc-ceed in particular environments. The currency is genes. Heritablevariation is our focus; but in complex social animals like ourselves,not only genetic but cultural heritability—learning—can be signifi-cant, and the interaction between cultural and genetic transmissioncomplicates analysis (discussed later in “Caveats andComplexities: Novelty and Learning”).

THREE COMMON PROBLEMS

OF INTERPRETATION

Oddly, some of the simplest explanations of behavior are proposedfor human behavior—surely a paradox, since our behavior must beat the complicated end of any behavioral scale. Many misunder-standings arise because of one of three problems: confusing proxi-mate triggers for behavior with their functional evolutionary causes;measuring reproductive costs and benefits incorrectly or sloppily,leading to confusion over whose costs and benefits matter; and failingto understand the impact evolutionary novelty can have on behav-ior. Let’s examine each of these problem areas in more detail.

Proximate versus Ultimate “Causes”

To understand why humans act as they do in particular circum-stances we’d better understand what we mean by why, because weuse it to mean different things, resulting in unnecessary disagree-ments. Why questions have two principal forms in biology: ques-tions about proximate triggers and questions about ultimate selec-tive causes. These two approaches are not alternative hypotheses(if one were true, the other couldn’t be), but complement eachother. The ultimate cause of a behavior’s existence, in evolutionaryterms, is always its effectiveness in getting one’s genes copied.Proximate triggers, the mechanisms or stimuli that cue or release


behaviors, are sometimes also called causes; they tell us what kindsof environmental factors are important.

Again, let us start with a simple nonhuman example. If we askwhy a bird migrates, one answer might be “changing daylengthcauses hormonal changes, triggering migration.” Both changingdaylength and changing hormones are proximate triggers. If wecould interview birds as we do ourselves, we might have anotherset of proximate causes, the equivalent of our reasons: “I reallyhate the cold,” “it makes me feel good,” “that way I get to see myrelatives.” All of these are proximate cues. They do not explainwhy individuals in this species migrate (as opposed to others whodo not), why not all individuals migrate, or why daylength (asopposed to temperature, some other cue, or a combination of cues)has become the trigger.

The ultimate cause of migration is a seasonal better-versus-worse geographic shift in foraging and nesting areas; individualswho seek the better areas, shifting seasonally, leave more descen-dants than those who remain in one area. (This is why insect-eat-ing birds of the northern hemisphere are likelier to migrate southin the winter than seed-eaters; insects are relatively unavailable innorthern regions during the winter). When daylength is the mostreliable predictor of these seasonal shifts, individual birds whouse it as a cue will fare better than those who use some other prox-imate cue or who fail to migrate. The benefits and costs of migra-tion in terms of survival and reproduction may differ substantiallyfor older, prime-age birds, compared with yearlings; in such cases,different categories of individuals are more or less likely tomigrate.

As we try to understand human behavior, it is crucial to differ-entiate proximate causes from ultimate causes, for they tell us verydifferent things. Ultimate arguments are based on the relativereproductive costs and benefits for individuals. Elucidating proxi-mate mechanisms can enrich our understanding, especially whenour primary concern is intervention (e.g., as in medicine or familyplanning). When we wish to understand the functional evolution-ary response, the evolutionary study of trait-environment correla-tions takes precedence. Answers to both kinds of why questions areimportant; however, no proximate cause will be maintained if itdoes not create an ultimate selective advantage. As one of my col-leagues is fond of pointing out, only a handful of the Shakers, whoimposed celibacy on their members, remain alive. That is why biol-ogists frequently focus on the ultimate causal relationships.


Who Helps and Cooperates? The Levels of Selection Problem

The evolutionary function of some behaviors is immediately clear:behavior that makes food-getting efficient, for example. But costlybehavior that helps someone else is often difficult to explain atfirst, and this topic is troublesome to many. Whose benefit drivesthe success of any strategy? The solutions reduce to the following:

1. Inclusive fitness maximization, or kin selection. Hamiltonnoted that not only one’s children but also other relativescarry copies of one’s genes; thus, helping relatives, evenwhen it might reduce one’s own fertility, can be geneticallyprofitable.14 This important insight solves many apparentproblems when we look closely at behavior. For example,Darwin worried about the fact that honeybees had manynonreproductive workers, who raised the offspring of oth-ers in the hive. Hamilton showed that, because of theirpeculiar reproductive system, female bees shared moregenes with their sisters than with their offspring. Thus, itcould pay a worker bee (always female) genetically to givenepotistic care rather than reproducing herself.

We expect organisms, including humans, to engage inactivities that benefit relatives; the extent to which this istrue will depend on the degree of relatedness, and the costof the behavior. There is a story (probably apocryphal) thatsomeone once asked the geneticist Haldane (who sharedHamilton’s insight) whether he would give his life for hisbrother. “No,” Haldane is supposed to have answered,“but I would for more than two brothers or eight cousins.”

2. Reciprocity. Sometimes we help individuals who are clearlyunrelated. When help is never reciprocated, we lose—butmutual cooperation can be a highly effective competitivestrategy.15 Such cooperation, called reciprocity, occurs justwhere you would predict it—only in long-lived socialspecies in which individuals recognize each other and arelikely to interact repeatedly. Organisms in long-lived socialspecies, including humans, do things that help potentialreciprocators without immediate payback, if there is someprobability that there will be future interactions betweenthem. If individuals interact only rarely or occasionally,such indirect reciprocity is extremely vulnerable to cheat-ing; when this is true, individuals will mirror the behaviorof others in a “tit-for-tat”16 manner (I’ll start by cooperat-ing, but if you default I will, too). When risks are high andindividuals mobile, it is not surprising that helping behav-iors occur primarily among kin.


3. Group selection. The above helping strategies are clearlybased on genetic costs and benefits. In addition, there arefour quite different arguments about helping behavior thatare sometimes referred to as “group selection.” Generally,these attempt to explain how individually-detrimentalgenes (like a gene for total altruism) could spread in a pop-ulation. Although they are all called by the same name, thearguments and logic differ greatly. Wynne Edwards firstsuggested that animals might act against their own inter-ests in order to help the group, directly opposing the the-ory of natural selection.17 Three other arguments that arealso called group selection are logically consistent withordinary natural selection.

Wynne Edwards argued that groups have traits such as domi-nance hierarchies that are not a simple statistical sum of individualtraits, such that in any conflict situation the good of the groupwould prevail. Thus, he expected individuals routinely to payreproductive costs for the good of the group. He argued that ani-mals limit their individual reproduction for the good of the group,to keep numbers sustainable. Interestingly, Wynne Edwards arguedthat all species except humans were group-selected, because humanpopulations seemed not to be regulated. He proposed appropriatetests: For example, he suggested that not only should female prong-horn antelope in bad years try to avoid matings, but that evenstrong territorial males (who usually monopolize matings) shouldnot bother to mate. No such observation has been found, highlight-ing the problem that highly fertile “cheaters” would win if there isno individual disadvantage to high fertility. In fact, natural popula-tions are not particularly stable.

Wynne Edwards’ theory has been invoked to explain why sofew children are born in societies like the !Kung. However, we mustask whether low fertility means low fitness. Careful empirical work(see “Optimizing Maternal Effort: Spacing Children”) shows thatwomen with longer interbirth intervals, and thus rather low fertil-ity, actually have more surviving children. They are more, not less,fit. Thus what looked like an individual disadvantage in fact turnsout to be an individual advantage in that environment.

Sometimes the group may seem to benefit as a result of thecumulative selection on individuals even though natural selectionhas acted on the level of the individual. It is important to test, ratherthan to assume, what the costs and benefits are. Although someanthropologists have uncritically accepted Wynne-Edwards’ model,Hawkes and Charnov18 have clearly shown its fallacies for humans.


The three other arguments often called group selection allconsider genes (like natural selection), and all assume naturalselection is working. Coalition group selection is really a specialcase of reciprocity, but I put it here because it is sometimescalled group selection.19 An example is laws by which within-group coalitions of some individuals in the group constrain thebehavior of other individuals in order to seek their own interests.Interdemic group selection, simply stated, predicts that if certainconditions are met, the structure and composition of groups(demes are small groups) can influence the frequency of genes.20

Within each group, altruists lose to selfish-gene lineages. Theconditions under which deleterious genes could spread are veryrestricted: There must be a number of small, viscous (inbred)groups close to each other, and occasional mixing of groups fol-lowed by restricted interchange. Because differential successoccurs at birth and death (and the group equivalents of these),and because the turnover of individuals within groups is somuch more rapid than the turnovers of groups, a bias exists forselection to be more powerful at the level of individuals. Thus,this model is logical and consistent, but unlikely to be widelypowerful. Culture-gene interplay theory says that because therules for cultural transmission and genetic transmission may dif-fer, even under the same selective pressures, different geneticequilibria could result from cultural versus genetic selection.21

Boyd and Richerson note that this model of group selection,when applied to altruistic behavior “clearly is not verified by thedata concerning ethnic cooperation among humans.”22 Thismodel, like interdemic selection, is logical but unlikely to bewidely powerful.

All explanations for the question of why individuals help oth-ers, except Wynne Edwards’s, acknowledge that ordinary naturalselection operates. The bottom line is that only behaviors thatenhance the success of a genetic lineage (such as behaviors that areselfish, parental, reciprocal, or help relatives and therefore enhanceinclusive fitness) can evolve by natural selection. Cultural inven-tion and cultural transmission can certainly give rise to behaviorsthat would not be favored by natural selection. But, because of nat-ural selection, these behaviors are not likely to become common, orto replace genetically profitable behaviors. The general consensusis that ordinary individual selection will be relatively muchstronger than such interdemic selection under all but the mostrestrictive conditions.


Caveats and Complexities: Novelty and Learning

We humans change our environment more, and more rapidly, thanany other species—and when the environment changes, previouslyadaptive behaviors can lose their advantage. This creates enor-mous complications for analyzing our behavior. Imagine a behav-ior (eating sweet fruits) that has enhanced fitness (better survivor-ship) for a long time. Fruits are full of fiber and vitamins—andthey are sweet. Now we invent refined sugar and create a new con-dition: We have super-sweet, super-delicious foods that are actu-ally full of empty calories and bad, not good, for us. Yet, like otherorganisms, we did not evolve to be aware of ultimate selective rela-tionships—just the proximate cues, correlated things that we cansense (e.g., pain from burns, pleasure from sex). That is why, ingeneral, we like things that are good for us. But when conditionschange, a behavior may continue to be driven by proximate cues(pleasure in delicious taste), even though these are now unhingedfrom the past functional advantage. Today we retain a preferencefor sweet taste that can be counteradaptive; the results includehealth risks and obesity. Humans create novel environments, andso it is likely that we can identify numerous behaviors, particularlyin modern societies, that do not have current reproductive benefit.

UNEXPECTED PREDICTIONS

FROM A BEHAVIORAL

ECOLOGICAL APPROACH

Were We Ever Really Conservationists?

Behavioral ecology presents a challenge to our conventional wis-dom about the way humans used resources in the past, comparedto today. For example, what about the idea that people in tradi-tional societies, being more directly and immediately dependent onthe ecology of the natural systems around them, were more con-serving and respectful of those resources? This is the EcologicalNoble Savage concept.23 Yet if human resource use has followed


behavioral ecological rules, people are unlikely to give up short-term individual or familial benefits for long-term societal or globalgains, and this is likely to have been true throughout our history asa species, rather than a new phenomenon associated with newtechnology. Behavioral ecology generates alternative testablehypotheses about conservation:24

1. Deliberate exploitation in traditional societies is predictedwhen (a) it yields individual genetic profit (and/or itsproximate cues, status or wealth enhancement), and (b)technology is sufficient to accomplish exploitation.Resources are most conservatively used when there israpid and clear feedback regarding the impact on familyand individual welfare (when overexploitation carries clearindividual and familial costs). If too-heavy hunting meanslean times soon, conservation is likely.

2. High density population and/or very efficient technologymay lead to overexploitation and environmental degrada-tion if there is profit. For example, Great Lakes Indian soci-eties had quite sufficient technology to wipe out residentbeaver populations, but until the Hudson’s Bay Companyarrived to provide an insatiable market, there wasn’t muchone could do with the thirtieth beaver pelt (given a market,one could turn it into fishhooks or tobacco). The impact ofnew, more efficient technologies will vary, depending onwhether their use results in greater (short-term) individualand familial benefit.

Cross-culturally, expressions of conservation (e.g., reasons toleave some resource untouched) are very rare; only about 5 percentof societies have such rules.25 Resource-use patterns have verystrong ecological correlates, but expressions of conservation do not.And finally, a conservation ethic does not, in fact, appear to resultin broad protection of the resource base. In detailed studies of indi-vidual cultures, many follow the predictions of optimal foragingtheory (maximizing individual and familial returns for effort), butso far no analyzed culture has shown any evidence of long-termconservation (e.g., avoiding killing a rare species if it is encoun-tered, or avoiding killing pregnant females).26 These findings, pre-dicted from behavioral ecological theory, suggest that while wemay have evolved to be efficient resource-getters, and perhapsgood short-term environmental managers, we have no history offar-sighted global conservation.

Misunderstandings arose because low consumption was takento imply a conservation ethic. Three things interact to cause somelevel of consumption: population level, level of available technology,


and profit. When there are few people, particularly when there isinefficient technology and low profit, consumption will be low—not because of a conservation ethic, but because a small group ofpeople with low technology cannot overexploit.

The Ecology of Mating Systems

Plural marriage (polygamy) is common, but there is a very strongbias. Polygyny (one man married to more than one woman) is com-mon ( allowed in about 93 percent of societies), but polyandry (onewoman married to more than one man) is very rare. Perhapsbecause polygyny is so common, we rarely ask why, though culturalanthropologists know much about the patterns, and the correlates,of polygamy.27 But behavioral ecology makes some startling andunforeseen predictions about the ecology of mating systems. Forexample, the kind of polygyny—whether men are polygynous bycontrolling mates (harems) or resources (resource-based polyg-yny)—has ecological correlates (e.g., are resources like cattle defensi-ble?), just as in other species. And there is a strong relationship pre-dicted between serious pathogens and parasites (things like sleepingsickness), and polygyny, which holds even within geographic areaand inside the tropics (two possible complicating factors).28

Why does behavioral ecological theory make such unex-pected predictions? Pathogens, because they are living, evolving,biological entities, pose greater uncertainties than those of simplephysical unpredictability.29 Why would polygyny be favored? Ifwomen can raise children more successfully with the help of men,and if pathogens are serious, a woman may be better off tobecome a healthy man’s second wife than the first wife of aninfected man (in other species, this is called the polygyny thresh-old).30 From a man’s point of view, because pathogens are anuncertainty, getting genetically more variable children would bereproductively profitable when pathogens are serious. However,we must be careful: A successfully polygynous man has morechildren, as well as more variable children, than a monogamousman. Fortunately, there is another test. Cross-culturally, somesocieties have a preference for marrying sisters (sororal polyg-yny). Since children of sisters will be genetically more alike thanchildren of nonsisters, we would expect that when pathogenstress is high, nonsororal polygyny would be preferred—and thisis exactly what we find.


Monogamy is less common than polygyny, for when somemen can profit from polygyny, we predict that they will. Thereseem to be two kinds of monogamy. One occurs in relatively low-productivity environments, in which men appear to gain morefrom investing in the children of one woman than from multiplematings—perhaps it is simply too expensive, and resources are toolimited, to be polygynous successfully. The second kind, socially-imposed monogamy, is characteristic of larger societies with rela-tively little class and caste distinction. In these cases, it is likely thatpowerful men are forced to give up some reproductive advantagesfor the sake of coalitions with other men. Even when monogamy ispreferred, those few men who can marry more than one wife do so,both concurrently and sequentially.31

Polyandry is rare in mammals, including humans, for impor-tant cost-benefit reasons: Men can have more children by havingmore than one mate, but women cannot. Thus, the conditionsunder which polyandry is reproductively profitable are very rare.Polyandry seems to occur in two ecological conditions. In quitemarginal environments, as for the Lepcha of northeastern India,brothers (kinship again) marry a single woman and work togetherto support her children, all of whom are considered socially tobelong to the elder brother. In other situations, polyandry appearsto concentrate the wealth of a lineage in a smaller number ofdescendants, effectively trading more children or grandchildrenfor fewer, extremely well-invested, ones.32

Optimizing Maternal Effort: Spacing Children

Earlier, I noted that behavioral ecologists suggest that havingfewer-than-possible children is typically an optimization strategy,rather than a sacrifice (as Wynne-Edwards would have it). Howcould this be so? A mother’s investment in one child comes at theexpense of investment in others, and closely spaced pregnancies,when nutrition or other factors are limiting, may result in loweredlifetime reproduction. Consider !Kung women, who have inter-birth intervals of about four years. This seems, at first, to representfar lower fertility than is possible, and this is why group-selectionarguments were made for the !Kung. But because predators areprevalent, !Kung women who depend on bush foods may carrytheir children at least occasionally for up to six years. Women withlonger interbirth intervals had more (rather than fewer) surviving


children. A woman’s “backload” (weight of child plus foragedmaterial) predicted the inter-birth intervals for each environment.33

!Kung women living in compounds, not dependent on bush foods,showed shorter interbirth intervals. Bush-living women maxi-mized successful descendants not by maximizing rate of births, butby responding to the conflict between production of a new childversus the cost of such production on the survivorship of otherchildren. (Refer back to “Who Helps and Cooperates? The Levelsof Selection Problem.”)

Nursing women can forage less than others.34 In some societies,these costs are partially defrayed by peer or sibling child care, andthe availability of peer or sibling caretakers can have an impact ona mother’s lifetime fertility. On the island of Ifaluk, for example, awoman’s lifetime fertility is correlated with the sex of her first twochildren; women whose first two children were girls have greaterlifetime fertility than others, because the (older) daughters could beasked to help with child care.35 Even grandmothers continue tocontribute to the welfare of their grandchildren, working and gath-ering more than nursing mothers.36

In some societies, having enough money to hire wet nursesdefrayed these costs. In the best-analyzed case the richest womenhad very short interbirth intervals, very high fertility, and lowinfant mortality; these richest women, who could afford the bestwet nurses, fared best.37 Among the bourgeois, complexities cre-ated more variation in pattern. Poor women had longer interbirthintervals, lower fertility, and high infant mortality; and the wetnurses fared worst of all, with very long interbirth intervals, verylow fertility, and very high infant mortality.

Abortion, Infanticide, and Abandonment

In other species, it is typically not parents but reproductive com-petitors (e.g., males taking over a harem) who commit infanticide,and this makes selective sense.38 Among primates, the overwhelm-ing majority of infanticides are committed by immigrant males, ormales who do not belong to the victim’s social group. In humans,also, stepparents are more likely to abuse or neglect children thangenetic parents. Even when socioeconomic factors are taken intoconsideration, the risk for being killed is seventy times as great ifthe child lives with a stepparent as well as its natural parent.39

Among the Tikopia and the Yanomamö, a man may demand the


death of his new wife’s prior children.40 Such cases dramaticallyreflect the conflict of genetic interests between the parent and thenonparent who may be called upon to invest in the children.

Yet parents can commit infanticide and abortion, and they canabandon their children. This seems counterselective, but becauseeach infant requires great care, investment biases, even to theextent of infanticide, can sometimes be reproductively profitable.41

Selective reasons for killing or abandoning a child include amother’s ability to invest, a mother’s access to additional resources(family, mate), a child’s ability to succeed, and the economic andreproductive value of other existing or future possible children.Cross-culturally, deformed or seriously ill newborns, those whohave least chance of succeeding, are at greater risk for infanticide.42

Similarly, when circumstances reduce a mother’s chance of suc-cessful care (e.g., too-close births, twins, lack of an investing male),infanticide or neglect is more likely. Abortion, too, is more com-mon when the birth of an additional child is likely to reduce themother’s lifetime reproductive success. As women age, and theirreproductive value declines, termination of investment is lesslikely. Even in our society, attitudes toward abortion are related tothe proportion of women in any group who are “at risk” ofunwanted pregnancy.43

Historical studies of child abandonment also reflect such selec-tive considerations as a mother’s ability to invest in the child(including own health, familial resources, economic conditions),and the child’s health, legitimacy, and sex. Child abandonment inhistorical France, Spain, and Russia was related to economic fac-tors, child’s condition, and mother’s abilities.44 In one study of childabandonment, 77 percent of cases were clearly related to maternalability to invest and offspring quality, despite crude data and greatvariation in time, country, and other circumstances.45

IDEAS FOR EXPLORATION

Precisely because human behavior is so diverse, it is useful to lookat it from a number of perspectives, with different levels of focus.The behavioral-evolutionary ecological perspective leads us to askquestions we might never ask otherwise, and can make sense ofpatterns that are otherwise puzzling. Behavioral ecologists studyadaptive behavior in the organism, without worrying too much


about whether it is genetic, learned, or contextual—what is impor-tant is that heritable variation exists, not exactly how inheritance ismediated (though that is another interesting question). We typi-cally assume Grafen’s46 phenotypic gambit and simply studywhether a particular trait or behavior enhances or reduces fitnessin a particular environment. This new perspective suggests thatthere may be a continuum from other species to our own, despiteour cultural complexity and variability, that we can use to analyzebehavior. Success in foraging, wealth-seeking, and other forms ofstriving increase reproductive success, especially for men. Sex dif-ferences in behavior may make some ecological sense, though wemust not commit the “naturalistic fallacy” (if it’s there, it should beso). We need to be careful and rigorous in our framing of hypothe-ses. It is also important to remember that we need not be bound byour evolutionary past, and that we live in environments that arenovel, compared to our evolutionary past.

The disagreements between behavioral ecology and more tradi-tional approaches are fewer than they seem at first sight. Some, likeWynne Edwards’, simply arise from a misunderstanding of defini-tions (i.e., producing fewer than the maximum physiologically pos-sible number of offspring is not necessarily a genetic sacrifice).Others are not disagreements at all: Fields like cultural anthropol-ogy look at the more proximate correlates of a behavior, whilebehavioral ecology makes predictions from the ultimate selectivepoint of view, and both fields could profit from sharing perspec-tives. Thus anthropologists note that men have a higher death ratethan women in most polygynous societies, and this results in fewermen being available as mates (a strong proximate correlate ofpolygyny).47 Behavioral ecology makes a reproductive cost-benefitargument; it notes that unless males can gain more throughparental care than through many matings (with all the risks matingstruggles incur) they will spend their reproductive effort in gettingmates (a high-risk, high-gain strategy) rather than in caring foryoung. Thus, the conditions favoring polygyny also favor riskybehavior in males, human or otherwise, and this means that males,in order to succeed in getting mates, must do many things thatseem counter to ordinary selection—wait until they have grownlarge in order to win fights over rivals (thus delaying reproduction),fight for status, power, or territory, and often risk death.48 Thus,behavioral ecologists and anthropologists generate complementaryexplanations at different levels for the same phenomenon.

Finally, behavioral ecology sometimes makes a priori predic-


tions, unexpected from any other paradigm, about behavior. Here Ihave concentrated on some examples of cross-cultural comparisonsand optimization models, and on more ecological rather than psycho-logical approaches to human behavior. Some very interesting newwork focuses on other problems, including: the optimality of forag-ing; why and how boys and girls are taught differently; the ecologyof warfare; moral systems as the societal outcomes of individual con-flicts of interest; why men and women are so different; and psycho-logical mechanisms (e.g., why it is so much easier for us to solveproblems when they are set in evolutionarily-relevant contexts).49

Exploring these new areas can prove exciting as well as useful.

NOTES

1. Charles Darwin, On the Origin of Species (London: Murray, 1859);The Descent of Man and Selection in Relation to Sex (London: Murray,1871); and The Expression of Emotions in Man and Animals (London:Murray, 1872).

2. Lee Cronk, “Human Behavioral Ecology,” Annual Review ofAnthropology 20 (1991): 25–53.

3. Edward O. Wilson, Sociobiology: The New Synthesis (Cambridge,MA: Harvard University Press, 1975).

4. A typical criticism of the adaptationist program is that of Steven J.Gould and Richard Lewontin, “The Spandrels of San Marco andthe Panglossian Paradigm,” Proceedings of the Royal Society ofLondon B 205 (1979): 581–598. Critical discussions and responsesinclude Richard Dawkins, The Blind Watchmaker (Essex: Longman,1986); and Helena Cronin, The Ant and the Peacock (Cambridge:Cambridge University Press, 1991), pp. 81–110.

5. Good discussions of hypothesis testing in the study of behaviorinclude: John Alcock, Animal Behavior, 5th ed. (Sunderland, MA:Sinauer, 1993), chapters 1 and 17; Eric A. Smith and BruceWinterhalder, eds., Evolutionary Ecology and Human Behavior (NewYork: Aldine De Gruyter, 1993), pp. 5–23; and Richard D.Alexander, “Evolutionary Approaches to Human Behavior: WhatDoes the Future Hold?” in Laura Betzig, Monique BorgerhoffMulder, and Paul Turke, eds., Human Reproductive Behaviour: ADarwinian Perspective (Cambridge: Cambridge University Press,1988), pp. 317–341.

6. Ibid.7. J. P. Rushton, “Race Differences in Behaviour: A Review and


Evolutionary Analysis,” Personality and Individual Differences 9(1988): 1009–1024.

8. Optimization is discussed well in Smith and Winterhalder,Evolutionary Ecology and Human Behavior, pp. 50–60. Comparativemethod is discussed by Richard D. Alexander, Darwinism andHuman Affairs (Seattle: University of Washington Press, 1979).

9. Mark Ritchie, “Optimal Foraging and Fitness in ColumbianGround Squirrels,” Oecologia 82 (1990): 56–67.

10. Bernd Heinrich, Ravens in Winter (New York: Summit, 1989).11. Richard Dawkins, The Selfish Gene, 2nd ed. (Oxford: Oxford

University Press, 1989).

12. Alan Grafen, “Natural Selection, Kin Selection, and GroupSelection,” in J. R. Krebs and N. B. Davies, eds., BehaviouralEcology: An Evolutionary Approach, 2nd ed. (Oxford: BlackwellScientific, 1984), pp 62–84.

13. Bobbi S. Low, “Ecological Demography: A Synthetic Focus inEvolutionary Anthropology,” Evolutionary Anthropology 1, no. 5(1993): 106–112.

14. William D. Hamilton, “The Genetical Evolution of SocialBehavior,” Journal of Theoretical Biology 7 (1964): 1–16, 17–52.

15. Robert L. Trivers, “The Evolution of Reciprocal Altruism,” QuarterlyReview of Biology 46 (1971): 35–57; Richard D. Alexander, The Biologyof Moral Systems (Hawthorne, NY: Aldine De Gruyter, 1987).

16. Robert Axelrod, The Evolution of Cooperation (New York: BasicBooks, 1984).

17. V. C. Wynne Edwards, Animal Dispersion in Relation to SocialBehavior (Edinburgh: Oliver and Boyd, 1962).

18. Kristen Hawkes and Eric Charnov, “Human Fertility: Individualor Group Benefit?” Current Anthropology 20 (1988): 469–471.

19. Alexander, The Biology of Moral Systems; W. Irons, “How DidMorality Evolve?” Zygon 26 (1991): 49–89.

20. Sewall Wright, “Tempo and Mode in Evolution: A CriticalReview,” Ecology 26 (1945): 415–419; William D. Hamilton, “InnateSocial Aptitudes in Man: An Approach from EvolutionaryGenetics,” in Robin Fox, ed., Biosocial Anthropology (New York:Wiley, 1975); D. S. Wilson, Natural Selection of Populations andCommunities (Menlo Park, CA: Benjamin Cummings, 1979);Wilson, Sociobiology: The New Synthesis.

21. Robert Boyd and Peter Richerson, Culture and the EvolutionaryProcess (Chicago: University of Chicago Press, 1985); WilliamDurham, Coevolution: Genes, Culture, and Human Diversity(Stanford: Stanford University Press, 1991); C. J. Lumsden and


Edward O. Wilson, Genes, Mind, and Culture (Cambridge, MA:Harvard University Press, 1981).

22. Boyd and Richerson, Culture and the Evolutionary Process, p. 240.23. Kent Redford, “The Ecologically Noble Savage,” Orion 9 (1991):

137–154.24. Bobbi S. Low and Joel Heinen, “Population, Resources, and

Environment,” Population and Environment 15, no. 1 (1993): 7–41;Raymond Hames, “Time, Efficiency, and Fitness in theAmazonian Protein Quest,” Research in Economic Anthropology 11(1989): 43–85; Raymond Hames, “Wildlife Conservation in TribalSocieties,” in Margery Oldfield and Janis Alcorn, eds., Culture,Conservation, and Ecodevelopment (Boulder, CO: Westview Press,1991); Michael Alvard, “Testing the ‘Ecologically Noble Savage’Hypothesis: Interspecific Prey Choice by Piro Hunters ofAmazonian Peru,” Human Ecology 21 (1993): 355–387.

25. Bobbi S. Low, “Behavioral Ecology of Conservation in TraditionalSocieties,” Human Nature, in press.

26. Alvard, “Testing the ‘Ecologically Noble Savage’ Hypothesis,” pp.355–387.

27. See, for example, George Peter Murdock, Social Systems (New York:Free Press, 1949); Carol R. Ember and Melvin Ember, Anthropology,7th ed. (Englewood Cliffs, NJ: Prentice Hall, 1993); Melvin Emberand Carol R. Ember, Marriage, Family, and Kinship (New Haven, CT:HRAF Press, 1983); and Mark V. Flinn and Bobbi S. Low,“Resource Distribution, Social Competition, and Mating Systems inHuman Societies,” in Richard Wrangham and David Rubenstein,eds., Ecological Aspects of Social Systems (Princeton: PrincetonUniversity Press, 1986), pp. 217–243.

28. For the general arguments, see Cronk, “Human BehavioralEcology,” pp. 25–53; and Monique Borgerhoff Mulder,“Reproductive Decisions,” in Eric A. Smith and BruceWinterhalder, eds., Evolutionary Ecology and Human Behavior(Chicago: Aldine, 1992), pp. 339–374. For the parasite correlations,see Bobbi S. Low, “Marriage Systems and Pathogen Stress inHuman Societies,” American Zoologist 30 (1990): 325–339; andBobbi S. Low, “Pathogens and Polygyny in Humans,” in LauraBetzig, Monique Borgerhoff Mulder, and Paul Turke, eds., HumanReproductive Behaviour: A Darwinian Perspective (Cambridge:Cambridge University Press, 1988), pp. 115–127.

29. Bobbi S. Low, “Human Responses to Environmental Extremenessand Uncertainty: A Cross-Cultural Perspective,” in ElizabethCashdan, ed., Risk and Uncertainty in Tribal and Peasant Economies(Boulder, CO: Westview Press, 1989), pp. 229–255; Low, “MarriageSystems and Pathogen Stress in Human Societies,”pp. 325–339.


30. The original description of polygyny threshold was that ofGordon Orians, “On the Evolution of Mating Systems in Birds andMammals,” American Naturalist 103 (1969): 589–603. It is applied tohuman systems in Mulder, “Reproductive Decisions,” pp.339–374.

31. Richard D. Alexander, John L. Hoogland, Richard D. Howard,Katharine M. Noonan, and Paul W. Sherman, “SexualDimorphism and Breeding Systems in Pinnipeds, Ungulates,Primates, and Humans,” in Napoleon A. Chagnon and WilliamIrons, eds., Evolutionary Biology and Human Social Behavior: AnAnthropological Perspective (North Scituate, MA: Duxbury Press,1979); Bobbi S. Low, “Measures of Polygyny in Humans,” CurrentAnthropology 29, no. 1 (1988): 189–194.

32. William Durham, Coevolution: Genes, Culture, and Human Diversity(Stanford: Stanford University Press, 1991); M. Goldstein, “Pahariand Tibetan Polyandry Revisited,” Ethnology 17 (1978): 325–337; N.E. Levine, The Dynamics of Polyandry: Kinship, Domesticity, andPopulation on the Tibetan Border (Chicago: University of ChicagoPress, 1988).

33. Nicholas G. Blurton Jones, “Bushman Birth Spacing: A Test forOptimal Interbirth Intervals,” Ethology and Sociobiology 7 (1986):91–105; N. G. Blurton Jones, “Bushman Birth Spacing: Direct Testsof Some Simple Predictions,” Ethology and Sociobiology 8 (1987):183–203.

34. A. Magdelana Hurtado and Kim Hill, “Tradeoffs between FemaleFood Acquisition and Childcare among Hiwi and Ache Foragers,”Human Nature 3 (1992): 185–216.

35. Paul W. Turke, “Helpers at the Nest: Childcare Networks onIfaluk,” in Laura Betzig, Monique Borgerhoff Mulder, and PaulTurke, eds., Human Reproductive Behaviour: A Darwinian Perspective(Cambridge: Cambridge University Press, 1988), pp. 173–188.

36. Kristen Hawkes, J. O’Connell, and Nicholas Blurton Jones,Hardworking Hadza Grandmothers, in V. Standen and R. Foley, eds.,The Behavioural Ecology of Mammals and Man (London: BlackwellScientific, 1989), pp. 341–366.

37. Sarah Blaffer Hrdy, “Fitness Tradeoffs in the History andEvolution of Delegated Mothering, with Special Reference to Wet-Nursing, Abandonment, and Infanticide,” Ethology and Sociobiology13 (1992): 409–442.

38. Sarah Blaffer Hrdy and Glen Hausfater, eds., Infanticide:Comparative and Evolutionary Perspectives (New York: Aldine deGruyter, 1984); Martin Daly and Margo Wilson , “Child Abuseand Other Risks of Not Living with Both Parents,” Ethology andSociobiology 6 (1985): 197–210; Martin Daly and Margo Wilson,


“Children as Homicide Victims,” In R. J. Gelles and Jane B.Lancaster, eds., Child Abuse and Neglect: Biosocial Dimensions (NewYork: Aldine, 1987), pp. 201–214.

39. Martin Daly and Margo Wilson, Homicide (Hawthorn NY: Aldinede Gruyter, 1988).

40. Daly and Wilson, Homicide. 41. See review by Low, “Ecological Demography: A Synthetic Focus

in Evolutionary Anthropology,” pp. 106–112.42. Daly and Wilson, Homicide.43. Elizabeth Hill and Bobbi S. Low, “Contemporary Abortion

Patterns: A Life History Approach,” Ethology and Sociobiology 13(1991): 35–48. Laura Betzig and L. Lombardo, “Who’s Pro-Choiceand Why,” Ethology and Sociobiology 13 (1991): 49–71.

44. R. Fuchs, Abandoned Children: Foundlings and Child Welfare inNineteenth-Century France (Albany: SUNY Press, 1984); J.Sherwood, Poverty in Eighteenth-Century Spain: Women and Childrenof the Inclusa (Toronto: University of Toronto Press, 1988); D.Ransel, Mothers in Misery: Child Abandonment in Russia (Princeton:Princeton University Press, 1988).

45. John Boswell, The Kindness of Strangers: The Abandonment ofChildren in Western Europe from Late Antiquity to the Renaissance(New York: Vintage Press, 1990); See review by Low, “EcologicalDemography: A Synthetic Focus in Evolutionary Anthropology,”pp. 106–112.

46. The phenotypic gambit assumes that the phenotype (what you cansee about the organism) reflects its genotype, or genetic composi-tion, and that the organisms we see have nonrandom characteristicsarising from particular genes interacting with particular environ-ments. This allows us to ask, “What kinds of traits or characteristicswork better in this particular environment?”—even when we can-not specify what particular gene or genes produce those characteris-tics. The phrase phenotypic gambit was coined by Grafen, “NaturalSelection, Kin Selection and Group Selection,” pp. 62–84.

47. Melvin Ember, “Warfare, Sex Ratio, and Polygyny,” Ethnology 13(1974): 197–206.

48. Bobbi S. Low, “An Evolutionary Perspective on War,” in WilliamZimmerman and Harold K. Jacobson, eds., Behavior, Culture, andConflict in World Politics (Ann Arbor: University of MichiganPress, 1993). For the underlying general arguments, see Cronk,“Human Behavioral Ecology,” pp. 25–53; Mulder, “ReproductiveDecisions,” pp. 339–374; Low, “Ecological Demography: ASynthetic Focus in Evolutionary Anthropology,” pp. 106-112;and Matt Ridley, The Red Queen: Sex and the Evolution of HumanNature (New York: Viking, 1993).


49. For general arguments, see Martin Daly and Margo Wilson, Sex,Evolution, and Behavior, 2nd ed. (Boston: Willard Grant, 1982); J.R. Krebs and N. B. Davies, eds., Behavioural Ecology: AnEvolutionary Approach, 3rd ed. (Oxford: Blackwell Scientific,1991); Smith and Winterhalder, Evolutionary Ecology and HumanBehavior; and Elizabeth Cashdan, ed., Risk and Uncertainty inTribal and Peasant Economies (Boulder, CO: Westview Press,1990). For foraging models see B. Winterhalder and E. A. Smith,eds., Hunter-Gatherer Foraging Strategies: Ethnographic andArchaeological Analyses (Chicago: University of Chicago Press,1981); For evolutionary psychology arguments, see JeromeBarkow, Leda Cosmides, and John Tooby, eds., The AdaptedMind: Evolutionary Psychology and the Generation of Culture(Oxford: Oxford University Press, 1992).

SUGGESTED READINGS

Alcock, John. Animal Behavior, 5th ed. Sunderland, MA: Sinauer, 1993,chapter 1, pp. 1–21, chapter 17, pp. 541–574. Here, treatment ofhuman behavior in a classic animal behavior text gives insight intothe behavioral ecological approach.

Betzig, Laura L., Monique Borgerhoff Mulder, and Paul Turke, eds.Human Reproductive Behaviour: A Darwinian Perspective.Cambridge: Cambridge University Press, 1988. Interesting collec-tion of empirical work—how to test hypotheses in the real world.

Cronk, Lee. “Human Behavioral Ecology.” Annual Review ofAnthropology 20 (1991): 25–53. Probably the best short, easy-to-readoverview of the general issues.

Daly, Martin, and Margo Wilson. Sex, Evolution, and Behavior, 2nd ed.Boston: Willard Grant, 1982. Easy to read, with many excellentexamples—makes the evolutionary continuity between humansand other species clear.

Dawkins, Richard. The Selfish Gene, 2nd ed. Oxford: Oxford UniversityPress, 1989. The classic statement of the selfish gene paradigm.

Smith, Eric A., and Bruce Winterhalder. Evolutionary Ecology andHuman Behavior. New York: Aldine de Gruyter, 1992. An editedcollection of optimality approaches to the behavior of humans(and related primates).


Research TOC

behavioral ecology “sociobiology,” h...

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