character of the issues - PDF document

aucial character of the issues & Williams' (1957) investigation of the enigma of sterile castes in eusocial stimulus for 186 JOHN TOOBY AND IRVEN DEVORE new phenomena. its worst, a conceptual model obscure; it unrealistic, or leaves unintegrated, known to yields conclusions that are Paradigmatic examples good conceptual models geometry, Dalton's chemistry, combined with genetics the Modem enormous array can be deduced a few tightly interdefined central Although referential models very useful where appropriate, medical research, their use in "behavioral paleontology" presents be carefully circumscribed. hominid evolution requires conceptual models. Although we far from achieving conceptual models that are both to create such models surely be more fruitful species as a distant past. choose a living species as a referential model once chosen, does one know along what dimensions the model species resembles the unobservable referent? real phenomena-baboons, chimpanzees, modern hunter-gath- arbitrarily defined which they doubt have in common with A conceptual living species extinct one, this conceptual model that there is validated principle appropriate living species a referential models is arbitrary. which parts are relevant display patterns intuitive. Consequently, large literature that discusses various and, at the baboons, bonobos, whatever, because they some trait the absence a sound conceptual model, there seems to the argument, assessing the probability assertion, or for substantive contribution progressive reconstruction hominid behavioral evolution. without a conceptual model, there are no between hominids Hominid Behavioral Evolution 187 and a model living species can hominids are bipedal: this make difference in whether dominance relations in baboons parallel dominance relations in hominids? hominid males were more predatory than baboon males, a conceptual to know. The absence legitimate method ferences between hominids proposed referential has several unfortunate on those heavily on ential research. referential models often to a dispropor- evolutionary period the model hominids is hypothesized a minimum, on the earlier more ape-like phases our evolution. Un- fortunately, this little light so signif- hominid lineage. were to learn hominid-pongid common ancestor, many most crucial questions about distinctively hominid evolution would we are humans and not or gorillas? more important, a referential perspective has differences, similarities are hominid evolution (such as high tool use, an immense expansion de-emphasized or neglected. Discontinuities between hominids catarrhines, such as high degrees carnivory, male parental investment, co- alitional intergroup ganisms are systems adaptations; a change resonates through system, changing other features the adaptive novel features frequently alter and meaning even identified similarities. Only explain uniquenesses; one cannot invoke their nature, referential or obscure important question human evolution: where most crucial and novel adaptations a referential conflated with, same as, a conceptual the referential species. So it was not simply savannah baboons that were proposed model for hominids, but a certain conception male dominance relations in baboons (Washburn and DeVore, 1961b). became less research perspective, pu- 190 JOHN TOOBY AND IRVEN DEVORE living species past species. present, we can discover shaped the past. The vary, only that govern how these each case. can estimate believed to be various points in their evolutionary history, the patterns primate homology (inves- behavioral, morphological, biochemical means), characteristics present paleontological record, archaeological record, ancient habitats. that the evolutionary principles possible hominid traits such future dis- about hominids uniquely determine about our evolutionary history. powerful conceptual model reconstructing hominid evolution does not yet well-developed form. Many components it already sohe a preliminary assembly its elements. Behavioral ecology, socio- evolutionary theory strategic modeling. Salient component theories 1964), reciprocal altruism (Trivers, 1971; Axelrod and Hamilton, 1981), parental investment, sexual selection, systems (Trivers, 1977), dominance (Parker, 1974; Popp and DeVore, 1979), foraging theory 1976), against predation (Curio, 1976), the ecology of disease and inbreeding avoidance (Tooby, 1982), strategies (Maynard Smith Price, 1973; Smith, 1982). component theories exist in a tentative form. good review exists. Therefore, a preliminary, exhaustive, list of strategic modeling prove useful. this stage, nothing more heuristic guidelines inference (a more Horninid Behavioral Evolution 191 detailed discussion strategic modeling hominid evolution I) approximate inclusive fitness maxi- Interactions between individuals are be analyzed in terms of inclusive fitness impact on the that increases between be- promoting inclusive is all is necessary or knowledge the strategy). strategies are incarnated differs includes morphological traits, and flavor preferences, complex but nonconscious learning mechanisms, mechanisms. However, contributed to the correlation strategies it may have played an increasing one-to-one correspondence between traits pressures, and there fundamental distinction morphological traits. Selection components that trait impacts. take an extreme change that makes costly will also increase the avoiding inbreeding winglessness in insects). related mates, therefore is, an adaptation to inbreeding avoidance. Individuals are selected their individual ation, not simply means that facultative strategists appropriate) rather committed to the same behavior or morphology. 6) The on the selective be a matter how common evolutionary history that situation has been, (in phylogenetic terms) been recurring, large its consequences are. Organisms adapted to common, important situations, reasonably adapted conditions and uncommon highly important conditions, uncommon, unimportant situations. 7) To extent made reasonable the considerations above, behavioral variation observed within groups, and between the same species initially have an effect either because costly, or because its The intensity of selection be a function consequences on various components variation in heritable traits (or more properly, heritable variation not explained is evidence not been acting on those traits very intensely or convergent evolution in parallel conditions direct must benefit the enhancing its eventual reproduction, eventual reproduction its relatives. This is particularly true patterned, nonhomologous ' is notable large number complex, costly, Systematic deviations from inclusive promotion are the phylogenetically rare individual competition with onto- genetic constraint, or intragenomic conflict (Dawkins and Krebs, 1979; Cosmides and Tooby, that are a trait need not advantageous under potential circumstance. need only This means that the frequency with which is advantageous, advantage, outweighs the frequency the cost. Thus, selection for a trait always against a probability distribution ancestral environmental and cannot this background. the above reasons, begins with the presumption that the great majority traits are these traits to construct a coherent descrip- investigator should attempt to adaptive consequences a feature. feature is not found (and validated), adaptation are ruled out, the nona- daptive nature will become such a to see how the larger devel- opmental, phylogenetic, adaptive patterns appears to the organism, but The Reconstruction a more encompassing system which the feature an inevitable concommitant. the feature under observation appears maladaptive, one investigates under other more conditions, the feature might under other, rarer conditions, might be compen- highly adaptive. investigate for evi- other conditions one investigates to the feature the product or physical constraint on adaptation. Adaptive any feature tures through appeal to nonadaptive aspects the evolutionary process remain alternative stochastic such as drift frequently invoked 1979) are almost the adaptationist traits as nonadaptive cannot supported without the adaptationist program. 17) There a strong underemphasized relationship between physiological) capacities adaptive strategies they pursue. enormous gap between knowing what habitat a species occupies, predicting its social other behaviors. Thus, communicative ability may also how they respond to the same pressure. The reason male coalitions intragroup are frequent savanna baboons but Hanuman different levels constraints on social cognition in the two groups. male coalitions chimpanzees may part to Therefore, as capacities increase diminish, the fitness and various strategies hominid evolution, ability to expanded enormously, and therefore communication would have appeared major impact on almost punish behavior that takes place in and what what has happened can become of negotiation. threats about what happen when punish behavior that paternity certainty 198 JOHN TOOBY AND IRVEN DEVORE organism correlates some degree with its fitness. 6 particular animal, it i actually control behavior. i behavior can t strategies allows approximate prediction. 1 proximate mechanisms, but only approximately fitness promoting strategies them. Evolutionary relates explanations I explanations in proximate mechanisms. Correct characteri- I t strategies gives precise i proximate mechanisms. a detailed analysis proximate mechapisms a species gives insight into 1 selective pressures that have traits of modern humans, including their powerful evidence past. Important clues strong male-female father- female aggression, the psychology male coalitions is a element in strategic mod- I species are used as the base to derive, test, refine, 1 evolutionary principles model. Although this data base allows kin selection, it is also primary source for principles, which in inferential re- search. Certain processes they cannot conceptually modeled measured directly. These processes so many interacting factors, which singly or together are little understood, direct observation primary or only sexual di- must be studied in this fashion. The differential impact possible existence limiting nutrients, ondary compounds, differential impact of predation, may all feed that are present knowledge is that these patterns are not directly derivable deductive framework, comparative approach is only method their investigation. among ho- uniquely derived features, non- i the comparative approach allows some in- i i i be made about functional (see Wrangham, this volume). the patterns among traits in related which traits tend to form adaptive constellations, traits are functionally hence mutually which traits may be developmentally linked, on each other. a series adaptations are present in they must mutually compatible. these kinds can occasionally quantitative inferences be made to partially known (e.g., hominid) species. such studies which kinds traits are conservative, which change track selective shifts more principles derived data are useful, they are far derived comparative all, probabilistic. specific case, because specific cases may have unique or can alter functional variables operate general relationship inapplicable or misleading. example, some (e.g., Zihlman, 1981) canine dimorphism in the hominid line a waning male-male competition, because correlation between these two variables cercopithicines. How- ever, as functional uses canines (attack, defense) may have been supplanted tools (Darwin, bipedal posture may from close combat, greater striking replacing canines as weaponry. tool use bipedalism are drastically increased in hominids, their functional appearance may render generalizations based primates inapplicable. This is an example why, ultimately, derived comparative relationships must be ultimately subsumed into) functional relationships. With a func- a unique element in deterministically. cannot explain hominid evolution that would equally impinged other species the same pre-adaptations: a theory why we are not our chimpanzees, gorillas, or bonobos. Unique adaptations evolutionary lineage. Prospective reconstructions of hominid adaptation must not only internally coherent, but they what was events that produced the hominids: bipedalism, high 202 JOHN TOOBY AND IRVEN DEVORE The Reconstruction of Horninid A description based on strategic eling would provide a can evolve into another across habitats. above (by deserve to be considered characterizing a primate species. is to hoped weighted or separated into that are prime a species' system that are fossil record, understanding the relationships of prime to secondary determinants be able infer those determinants that cannot be directly assessed from secondary factors reliable radiometric 1960s, evolution took span, rather in the to ten year period currently estimated. Although vast expanse time involved in recognized, certain habits thought shaped that narrow time frame still survive implicitly in much present hominid evolution. still com- press hominization a single rather than that it a large number discrete stages differentiated selective o om in id have not yet expanded to evolution. Although seriously argues a single "missing makes its many other to minimize (e.g., have tended generalized rejections evolutionary history. hominid evolution their inspiration (e.g., Tanner's [I9811 are treated generalized accounts often including even modern hunter-gatherers. actually involved in a series easy to see such generalizations are ill-founded. A feature, such seems to be inappropriate major adaptation chronospecies may be fully increasingly complete stratified i hominid evolution be regarded as a discrete series first place, that hominids bipedal at years (Johanson, Coppens, 1978), long before detectable stone tools, decoupled Darwin's compelling trinity brain expansion, at least in original trait requiring explanation. Sec- hominid species year range linear model species must in adaptive con- must morphologically different species at different times. Distinct fossil forms are now traits diverged sharply each other and from living animal. The teeth, limited cranial a family adaptive modes that are not human and response to many researchers a long the other. erer traits, such language, food-sharing backwards towards ape-hominid common ancestor, a slightly brainy, tool-using chimpanzee. methods, ancestors are reconstructed with a combination ape and human "Piltdown approach" ecology. Forms often considered intergraded series australopithecines as a midpoint, (e.g., Tanner, 1981). erectus as inept !Kung Strategic modeling requires a different approach The landscape hominid evolution linear, referential view accommodate; interpolating between "corridor" is seriously misleading. do not simply grade into which any feature is patible with co- only some clusters mutually consistent with each other and are therefore acceptable or hypotheses about a particular hominid or hom- Thus, each extinct form corresponds'to a distinct con- 206 JOHN TOOBY AND IRVEN DEVORE change markedly, rations to alter to continue, that drive them must also continue. This plant foods versus a number changes in underlying determinative surely relevant. denatures plant 1976), them more systematic use years ago) would alternative dietary constituents broader variety The disappearance Pleistocene megafauna would have changed hunting again possibly dramatically altering diets. changed over to be expected that hominids various stages very different animals, at least adaptations even from their direct precursors Sewall topography (Wright, 1951) hominid evolution: change in pay-offs or other variables make two previously compatible elements incompatible, the whole different configuration adaptive peak, potentially reversing earlier trends, in succession. this reason (considering large number variables regulating adaptation that to be different), it erectus even archaic sapiens were merely expansion in culture changed whole range it is surely unlikely organization remained uninfluenced these changes. The value is always to their hominid lineage, on the differences in behavioral-ecological variables, adaptive hypotheses given factor hominization must be evaluated separately each specific stage. Hypotheses must be linked discrete stages. Consequently, given this hominid evolution, (e.g., hunting, gathering) that are often treated traits present in modern humans ancestral stage, each trait must be know something powerful about ancestral hominids which alone cannot characterizing modern evolved sometime in the past, morphological traits profitable inferential characterize modern ancestral stage, then reason consequences that introduced have on the system that ancestral The zoologically explanation consistent with modern incidental, but our adaptive system. Consequently, the most telling hypotheses about hominid evolution they provide these divergent properties. how hominid adaptation propelled interrelating the prime determinants ioral ecology to our unusual traits. deal with human uniqueness principled way, these elements must be together into novel but lawful patterns. Such explanations not be hoc: novel features emerge naturally inextricable part rather than Powerful selection pressures were required to drive hominid lineage along so dif- path: any makes us other animals have addressed underlying our unusual trajectory. Close strategic analysis divergent features in terms consequences should transform the problem imponderable mystery sophisticated but straightforward unique hominid divergences include the following the ability to attain fitness goals situationally-tailored, instrumental sequences changing aspects the world (high causal the ability to communicate these models m language; 210 JOHN TOOBY AND IRvEN DEVORF or invented manipulations. The rapidity with which cogni- can circumvent genetically prey species accounts in extinctions that have are thousands of new manipulations, but also allow wide array adaptive problems. this lies causal or instrumental intelligence: to create and maintain cause-effect models prejudging which courses lead to which infinitely large number overwhelming majority maladaptive) "behavioral our innovative adaptive pattern. Our cognitive system is knowledge or information driven, potential responses behavioral sequences appropriate to bring course, exploration, trial are essential to themselves, they are to construct or anomalous features reveal themselves to objects instrumentally; acquisition is cognitive tools necessary to bring situation-specific manipulations. accident that language coe- or followed these cognitive innovations; language from animal communication systems in that it model-based information referring to cause-and- categories. This vastly increases niche, by drastically reducing information. The individual is longer limited by or the directly observes. animal occupying cognitive niche greatly favored: knowledge or model innovation can benefit individual, but its kin generations, adding a huge to counterbalance to the cognitive niche constitutes culture, which transmission between individuals information necessary to pursue terrestrial habitats is also liberation of fitness goals behavior- means that novel manipulations differing habitats. psychological mechanisms turned out Hominid be general solutions to adaptive problems, allowing us spread beyond our habitat Since such would be favored many kinds why did hominids evolve them not others? an animal not only know make, it must also be make them. The existence hands that are dexterous in their necessary precondition, limiting to certain primates, especially apes. Numerous vision and certain minimum body size are also probably important. Certain neural preadaptations are necessary, doubt, but such assertions remain vague great apes these preadaptations, develop along hominid lines? Chimpanzees, great apes, cause-and-effect-oriented cog- that parallel hominid lineage. possible answer sophisticated manipulations are possible from different such manipulations are more removed from many reasons: sharing, access other nonmoveable things such water, further bipedality evolved in the hominid line purpose (such as monitoring predators open savannah), would provide that differentiated information seeking. why gibbons, siamangs, and orangutans-solitary primates- did not more fully cognitive abilities increased pay-offs. metabolically costly organ (Martin, must be correspondingly high. may be must increase access to very food, such as meat. habitats are far more productive than tropical forests, that occupation the meat-rich differentiated hominids forest-bound apes. beyond its production the constituents brain require essential fatty acids, may prove real limiting made available by Entering the cognitive abilities behavior required cognitive abilities grow, broadening 214 JOHN TOOBY AND IRVEN DEVORE The Reconstruction coherent, a theory must account males to hunt and females to There are numerous other the human adaptations that collecting by continuous with great there is little in such a to explain differences other primates), females forage offspring. Although tools canying make foraging easier, this improvement seems to be changes in lineage-(or, did not hominid trajectory). There increased male parental investment with which males form agnatic kin-based or for the ease penetrate habitats without substantial plant resources. models provide persuasive se- females would bring plant foods feed parasitic males. There to explain sharing. Other primates share plant because: 1) it is unlikely that many plant foods aside bioenergetic costs differing aggressiveness lead to acquired foods labor inputs to be be readily consumed in quantities that are substantially greater can be burdensome) to about the to others. the gatherer models have systems where males associate with males invest little in to create intense male-male competition dimorphism. The the hominid lineage undermines assumption that low. The are gentle and the two perhaps in them anything but 1979a, sexually compete through aggressive male coalitions, in gorillas, system. Sug- (e.g., contradict knowledge that inbreeding transfer, especially among long-lived (Tooby, 1982). There nature and intersexual negotiation female choice): infanticide (as possibility'of meat provisioning, relationships (as (as 1983; Strum and Mitchell, this volume]), or the effects on females short, although undoubtedly have gathered plant foods from this single component hominid behavior seems wholly insufficient hominid evolution, proposed correlates "gathering hypothesis" characterization is modified great sexual dimorphism australopithecines is consistent robustus if so, likely resemble H. erectus any known H. such an exemplar. Lovejoy hypothesis. Lovejoy advanced a pair-bonding and prime movers. argues that innovation was a discontinuous increase in the system was monogamous, about the transition to bipedality. effort is to organize our understanding innovation (in factor in social life. inconsistent with several history theory, mating theory and the levelk implicitly invokes he has r and (MacArthur and Wilson, 1967; Pianka, 1970), seriously at argues that the orthogenetically driven de-sac, from which hominids escaped JOHN TOOBY AND IRVEN DEVORE were assumed to have gathered plant males to meat; individuals met home bases a sex-based is customary, attributed to preservational in the have begun entertain a alternative hypotheses about bones in these alternate scenarios (e.g., Isaac 1983a, 1983b, Potts, this Indeed, one problems with formulations was they hypothesized contemporary hunter-gatherers that which (in view) took place during stages depicts. Additional models stages must this approach is more a description an analysis the selection pressures shaped it. more precise and sharing is not, forager is laboring to not consume: this to be advantageous, the return must cost. Either equal value (exchange) or later equal or greater value must be provided (e.g., sexual access), or sharing must sufficiently benefit offspring (provi- or kin. answer imposes system, which should be spelled out. life, collected represents one kind used in a large ways. Provisioning young is not food sharing, not bring adults together (except mates selection, cross-sex food more limited, since adult members are pulled apart transfer. Adults be frequently separated from most a result, one than the other. provisioning based mating opportunities is possible, but does not explain with males constitutes another in this shifting marginal values different kinds at different times. must explain why other primates do Perhaps a diet on both and plant foods to a diet on either alone. involve the forager can plausible, they need to strategic model an entire about what sharing and addressed: how they invest? would females gain for repro- they gather they needed? how hominids evolved to such a stage must also and cautionary arguments about the possible misuse analogies between primate species modem hunter-gatherers hom- inid argues that there evidence indicating that extinct morphologically unlike living primate, therefore undoubtedly unique. points out widely accepted parallels between hunter-gatherers and adaptive syustems alternative interpretation for the evidential base the home scenario. Potts (1984b, proposes that instead Olduvai sites locations where tool making materials distant sources of raw materials. these stone they were processed. According to this an individual group established many such within its so that when they opportunistically acquired animal tissues, they bring them processing. Therefore, base" is on the presently available evidence. Moreover, evidence for carnivore faunal remains makes it unlikely that the (i.e., as home The most valuable aspect Potts' discussion his recognition 222 JOHN TOOBY AND IRVEN DEVORE gerous, given driving, ambush, most rapidly consumable is far less con- spicuous to scavengers search by scent, would be less draw them to vulnerable bases. Instead the opposed timid scavenger and the hunter, a fairer characterization would be the fearless scavenger. archeological finds indicate that meat bone handling were major activities. tool manufacture, stone transport over large distances raw materials, recurrent animal processing and the survived across that these activities were marginal nor Opportunistic scavenging with its rarity would not the expenditure skills this requires would far richer cut marks large to early hominids), observers would agree opportunistic scavenging meat occurred. is equally that the been lost battering stones, it seems equally clear were exploited for their marrow content (Isaac 1983b; Binford 1983, 1984). What remains at issue is scavenging behavior at the authors, beginning with Dar- (Darwin, 1871). was advanced in both so- Washburn Lancaster, 1968) sensational forms (Ardrey, 1961, 1976; Dart, 1953), fallen from cultural reasons (feminist quantitative analysis certain modern hunter-gatherer diets that plant foods provide calories. The hunting hypothesis in its extreme been regarded (Lovejoy, 1981; Shipman, with only notable exceptions 1982), been discarded downplayed in recent discussions strategic modeling to the issue the role indicates that, when considered in the certain compelling features that make its role necessary. Although only cursory analysis is possible here, clusions are hominid foraging, would elegantly economically explain large number unusual aspects hominid evolution: worth transporting and be accomplished an attractive alternative to additional competition Hunting provides ready explanation ering vegetable foods cannot plausibly match; foods large distances. through food mammals is rare in most likely Sexual dimorphism: The reduction sexual dimorphism across hominid lineage may explained through increased rental investment. most bioenergetically plausible form young through Male coalitions: and others have large game animals among the extended cooperation represents a phenomenon requiring explanation, major plausible the elaboration motivational substrate cooperation and coalitions must posit re- curring situations with and returns additional individuals. The only alternative (but and defense, as in chimpanzees. little limiting engaging in extensive relative rarity is far greater in than in other animal. Meat, unlike vegetable either captured the size the animal more on opportunities present themselves than the hunters. the other in more continuously graded quantities, and the quantity related to the expended and the 226 JOHN TOOBY AND IRVEN DEVORE much more meat other primate. divergent selection pressures are what are im- eat a large lowest estimates than that other primate, most temperate high latitude groups live almost exclusively animal products most or all year. Moreover, total caloric content is sole measure nutritional importance: may make calories least im- in optimal or successful reproduction. animal foods in the vitamins, trace minerals, essential fatty acids, calcium, and the to balance acid proportions to be examined contrasting plant foods with animal foods. Nutritional analysis needs to extend muscle tissues to include the nutritional internal organs grossest level, it is impossible for to live uncooked plant (e.g., cyanocobolamine deficiency). The view foods were hunter- gatherer diet based largely on Tanaka 1969, 1979, 1984; Tanaka, 1980). Although this nearly universal acceptance, it must be revised in the new data. Draper's press.) report on the !Kung at /Du/da, to the copious supplies !Kung at Dobe that the men / Du/da invest far far more success. Similarly, Silberbauer's (1981) G/wi, to Tanaka's the same population, reports a much higher rate dependence on much nearer hunting and !Kung at Nyae Nyae (Marshall, 1976). strategic ramifications hunting on adaptations in systematic combination, its explanatory power becomes only been space sketch in a relationships here, even such cursory examination shows that hunting has features compatible with the evolution, but distinctive properties or account many (though not all) unique features hominid sociality. primate-derived models particular primate species direct analogies fraught with problems, primates remain data from which explore comparative relationships, phylogenetic constraint relevant they provide important heuristic examples partial exploration certain issues which cannot be confidently Wrangham (this volume) uses phylogenetic comparison to identify possible conservative features organization in to characterize common ancestor. to this approach, shared features organization among humans, bon- obos are been present in common ancestor, behaviors likely to have characterized hominids at any evolutionary history. reviewing the available data, hominid-pongid common ancestor probably had closed social networks, male-dominated intergroup aggression, female transfer, a Wrangham's study constitutes innovative contribution, provide important supplementary evidence to guide hominid behav- reconstruction. However, notes, this ap- applied to these hominoids is in its infancy and adequate data are presently lacking, especially open coun- there are a number that must be kept in mind. first is simply statistical or to be developed, each estimated. compared is small, and the held in common are inevitably produce features vary rapidly along commonalities are produced entirely chance rather common ancestry. Wran- gham's list eight were considered similarities among, and humans, might also generate a these probabilities are to quantify, to select several sets well-studied primate and see many features from the same master are held among each set. Although it is likely that many are genuinely produced 230 JOHN TOOBY AND IRVEN DEVORE males differentially differentially with with females with whom they term relationships. their careful con- more sophisticated picture social life, increasing recognition and that aggression is only Additional dimensions in- individual females male aggression, meat sharing between males social knowledge, social skills, residency, cooperation, intercontingent negotiation social life. valuable observations a surer prospectively delivered assistance is "paid" for by copulations or female con- male from female cheater? How are such exchanges can male investment reciprocity by or years? such questions prove vital to behavioral reconstruction, because true evolutionary parallel might be found incipient form such male-female friendships existing in a among more solitary primates such as Monogamous primates. issue more central to hominid social systems than that volume) addresses an array this issue. central features monogamous mating poverty (or simplicity) of primate monogamy, resulting from its evolution solitary ancestral conditions. naturally raises hominid monogamy precipitate out larger social social system (like long term associations and consortships among baboons or bonobos), or did, system to include other members hominid monogamy orig- inated inside larger social group, dynamics structuring male- relationships would been considerably different those governing mating initially solitary primates the male to mother- dyad, and whose social size through retaining at the ot There are dimensions relevant human and male-female relations and the monogamy. They be inventoried with the following series exclusively with single male? male mate exclusively with single female? males invest in their their mates can unassisted females raise offspring? there only breeding female in there only breeding male in the two mates their relationship? species facultative in their selection are unique in simultaneously practicing multiple breeding males females in the same at least limited duration) individual females frequently simultaneous The features unique mating system are not other primate, are not "monogamy", especially statistical distribution deviations on the selection pressures constituting unusual behaviors, look to many different primate systems to component parallels, requires behavioral all work Common chimpanzees, bonobos and savannah baboons manifest extended relationships between individual males larger social groups. Gibbons and primates practice sexual exclusivity. Hamadryas baboons have females male, while be monogamous, now polyandrously to have several males attached to and (Sussman this volume). Although many aspects mating systems and their consequences are beginning to be understood (e.g., the reduction sexual di- morphism in monogamous the relationship between need to be sorted include the determinints female-female tolerance and intolerance in neotropical monogamous and polyandrous species), female the inhibition determinants that lead to low female male assistance. However, perhaps the single with high sexual exclusivity. What role changes may to be parasite pressure. However, this provide interesting data about Mozpho-behavioral Analysis Sussman (this vol- ume) proposes on the conservative features digestive tract. On the a pre- liminary, allometrically corrected, comparative analysis portionate potential gastrointestinal compart- Sussman found that faunivorous mammals. This consistent with a1 (1985). However, Sussman chosen to unfortunately be environmentally malle- may not after all tell us about ancestral diets. Sussman's method, commend it. it could given ancestor's (i.e., 4096 necessary for would be that has conservative aspects our dietary physiology biochemistry may ultimately reveal a nutritional requirements provide in what must be supplied in what can be and what must be present to synthesis all constitute information on ancestral animal can afford to lose ability to synthesize a nutrient reliably present in animal must available dietary substrates essential but always lacking potentially reveal considerable information on the structural fats, minerals (especially and amino all provide a starting point. The also prove be highly revealing: function digestive all provide compelling evidence that a protein, sugar, differentially absorbed, in a hierarchy. Presumably, more important acid is, digestive system selected to absorb acids in ancestral diets might be such a hierarchy. matching it against The Reconstruction Horninid Behavioral Evolution various foods uncooked fruits, tubers, shoots, leaves, bulbs, seeds, meat, heart, brain, blood, marrow, can settle about recent hominid diet. Strategic modeling the potential resolving a number thorniest issues concerning (e.g., 1976; Harris, notion that, to intelligence and behavior has forces. They argue simpler primate be- havioral mechanisms to more elaborated modern humans, a boundary was crossed. Many this, almost as a watershed transition that places in another entirely, beyond the capacity ethological methods to study, model They take humanity to mean that evolutionary terms. among primates, modeling. Essential strategic modeling is evolutionary ends. Proximate mechanisms are selected ("designed") inclusive fitness. intrinsic to the proximate mechanisms fitness is promoted change such as onto- genetic constraints, and the preadaptations (exaptations (exaptations and Vrba, 19821). The elaboration of mechanisms from the simple into changes only not the such changes will occur only when increase inclusive when they better promote the Humans are a remarkable expansion in intelli- consciousness (however defined), learning, and a sophisticated coe- motivational system. the analysis these mechanisms, precisely because anisms in terms evolutionary ends, intelligence, learning, consciousness motivational systems gressively become more sophisticated, they according to same evolutionary only on mechanisms, unprecedented