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Who says that research on humans cannot yield general principles? A recent paper by Zhou et al. (2005) shows that "Collating a variety of measures collected under a wide range of conditions and in different countries [documents] a coherent set of characteristic group
Robin Dunbar
Robin Dunbar.
sizes organized according to a geometric series with a preferred scaling ratio close to three. The fact that the signature of this scaling ratio comes through so strongly despite the fact that the data derive from a variety of different small- and large-scale societies suggests that it is very much a universal feature." (p. 442). Although these researchers conclude that "At present, there is no obvious reason why a ratio of three should be important.", there is, of course, a very large literature on the importance of "triadic" relations in primatology (e.g., Kummer) and other species (chickens). Is it possible that vertebrate brains code information in triads and combinations of triads (absolutely or relatively)? Time will tell.
* Zhou, W.-X, Sornette, D., Hill, R.A., & Dunbar, R.I.M. (2005). Discrete hierarchical organization of social group sizes. Proc. R. Soc. B, 272, 439-444.

The topics of alternative reproductive behaviors, tactics, and strategies continue to attract the attention of behavioral ecologists and sociobiologists as indicated by a forthcoming book to be edited by several major researchers (e.g., Joan Strassmann and Michael Taborsky) which is sure to become a classic. In addition, Plaistow et al. (2004) have recently contributed an important paper titled, "Evolution of alternative mating tactics: Conditional versus mixed strategies." These authors' treatment evaluates the conditions under which both types of polymorphisms are likely to occur. Applying ESS modeling, Plaistow et al. show that "equilibrium populations may frequently consist of a mixture of conditional and pure strategists." Further, the occurrence of conditional strategists is expected to be a function of reproductive skew. These findings have important implications for the expression of conditional strategies in primates who are very likely to exhibit intermediate levels of skew. The paper by Plaistow et al. also extends previous work on alternative reproductive behaviors in primates (e.g., Jones & Agoramoorthy, 2003: Chapter [PDF: 529K] and Table I [PDF: 11K]), including general properties of these responses across taxa.
* Jones, C.B., & Agoramoorthy, G. (2003). Alternative reproductive behaviors in primates: Towards general principles. In C.B. Jones (Ed.), Sexual selection and reproductive competition in primates: New perspectives and directions (pp. 103-139). Norman, OK: American Society of Primatologists.
* Plaistow, S.J., Johnstone, R.A., Colegrave, N., & Spencer, M. (2004). Evolution of alternative mating tactics: Conditional versus mixed strategies. Behavioral Ecology, 15, 534-542.

Two recent papers highlight the importance of studying primate populations in relation to guilds as well as community and ecosystem ecology. In one paper, Kerstiens et al. (2004) show that folivores influence the physiological responses of trees which in turn modify soil biological processes. Research is needed to assess the extent to which primates might be affected by and important to these processes. In a second paper, Ellwood & Foster (2004) show that the biomass of insects is more than 2 times current estimates. Since insects are major competitors of many primate species (e.g., howlers: Jones, 1995; also see Fleagle et al., 1999), these results may have significant implications for primate population numbers, foraging tactics and strategies, and the like.
* Ellwood, D.F., & Foster, W.A. (2004). Doubling the estimate of invertebrate biomass in a rainforest canopy. Nature, 429, 549-551.
* Fleagle, J.G., Janson, C., & Reed, K.E. (eds.) (1999). Primate communities. Cambridge: Cambridge University Press.
* Jones, C.B. (1995). The potential for metacommunity effects upon howler monkeys. Neotropical Primates, 3, 43-45.
* Kerstiens, G., Ayres, E., Heath, J., Possell, M., Black, H.I.J., & Bardgett, R.D. (2004). Tree physiological responses to above-ground herbivory directly modify below-ground processes of soil carbon and nitrogen cycling. Ecology Letters, 7, 469-479.

Data from primate societies suggest that infanticide by males is most likely to occur in single male ("harem")-multifemale groups. Broom et al. (2004) attempt to model the conditions accounting for the infrequent occurrence of infanticide in multimale-multifemale groups. Beginning with the assumption that paternity certainty is lower [on average (Editor's note)] for males in multimale-multifemale groups, these authors utilize several input parameters [infant mortality, reduction of interbirth intervals (IBI), lifetime reproductive success, and contribution to the gene pool] with an ESS treatment.
Reinmar Hager and friend
Reinmar Hager and friend.
These models provide a good fit to variations in the occurrence of infanticide observed in primate field studies and show that the benefits to infanticidal males are, particularly, governed by reductions in IBIs. These results are also consistent with Taborsky's [2001; also see Jones and Agoramoorthy, 2003 (full citation here)] schema to describe male alternative reproductive strategies [bourgeois (i.e., infanticidal), parasitic (i.e., subordinate), and cooperative] and should also be assessed in relation to the recent paper by Hager and Johnstone (2004) showing that "high levels of infanticide tend to occur only when discrimination is poor, costs of offspring production are low, and/or relatedness is low."
* Broom, M., Borries, C., & Koenig, A. (2004). Infanticide and infant defence by males--modelling the conditions in primate multi-male groups. J. Theor. Biol., 231, 261-270.
* Hager, R., & Johnstone, R.A. (2004). Infanticide and control of reproduction in cooperative and communal breeders. Anim. Behav., 67, 941-949.
* Taborsky, M. (2001). The evolution of bourgeois, parasitic, and cooperative reproductive behaviors in fishes. J. Heredity, 92, 100-110.

My favorite paper of 2004 is Rufus A. Johnstone & Redouan Bshary's, "Evolution of spite through indirect reciprocity [reputation]" (Proc. R. Soc. Lond. B, 271, 1917-1922). Reading and re-reading of the literature on human "cooperation" [see, for example, Ernst Fehr & Simon Gachter (2002) Altruistic punishment in humans. Nature, 415, 137-140] leads one to wonder whether humans may be behaving spitefully rather than cooperatively in many of the experimental conditions. Indeed, the recent paper by de Quervain et al. [(2004). The neural basis of altruistic punishment. Science, 305, 1245-1258] indicates that the (neural) reward systems for "altruistic punishment" and for "spite" are the same, a condition that may hold, as well for "indirect reciprocity" and "spite." In their theoretical treatment, Johnstone & Bshary conclude that, "existing theory suggests spite is unlikely to persist, but we demonstrate that it may do so when spiteful individuals are less likely to incur aggression from observers (a negative form of indirect reciprocity)" (p. 1917). Research is needed on the physiological, phenotypic, and adaptive relationships between "cooperation" and "spite" in order to obtain a more complete understanding of human--and other vertebrate--social behavior.

A recent article in TREE discusses the utility of modeling complex systems designed for experimental analysis (manipulation)--as opposed to models intended to fit data. In the author's words, "Simulation can add to theory development and testing, can offer hypotheses about the way the world works, and can give guidance as to which data are most important to gather experimentally."
* Peck, S.L. (2004). Simulation as experiment: A philosophical reassessment for biological modeling. Trends in Ecology and Evolution, 19, 530-534.

Primatologists and psychologists will want to read the paper by Gardner and West titled, "Cooperation and punishment, especially in humans." In this paper, these authors provide (theoretical) results showing "how the fundamental factor driving the evolution of social traits is a correlation between social partners and how this can arise for reasons other than genealogical kinship." The "rub" leading Gardner and West to investigate cooperation and punishment is that "punishing behavior is often costly for the punisher;" thus, it has been difficult to explain how costly behavior (e.g., altruistic cooperation) benifiting another could evolve. This paper will be of interest to anyone concerned with the proximate and ultimate domains of punishment and negative reinforcement (Jones, 2002), and it demonstrates clearly (as do several other papers) how cooperation may be viewed as compliance.
* Gardner, A., & West, S.A. (2004). Cooperation and punishment, especially in humans. American Naturalist, 164, 753-764. [Here is the link to the abstract.]
* Jones, C.B. (2002). Negative reinforcement in primate societies related to aggressive restraint. Folia Primatologica, 73, 140-143. [See first paragraph of Brief Report.]

An important group of commentaries is currently available online (but in a non-printable PDF format) at the website of the Finnish journal, Annales Zoologici Fennici [42(6), 2005]. Several high profile sociobiologists and behavioral ecologists (e.g., Sherman, Wicslo) discuss "eusociality," in particular, its definition and appropriate applications. Note, especially, the brief contribution by Bernie Crespi [PDF] (pp. 569-571) who presents what may be the best tripartite classification of social systems we are likely to achieve. Discussing "unambiguous convergence on small suites of core social traits" (p. 570), Bernie conceptualizes these taxa as three groups: (1) eusocial (permanently distinct types, as, castes); (2) cooperative breeders (temporarily distinct types); and, (3) communal (social species with one type of individual who both helps and engages in reproduction). The latter category may include most social mammals, including primates (not excepting humans) characterized by condition-dependent and/or facultative responses. These taxa are likely to display moderate to low levels of reproductive skew.

Commenting on a new book by Evelyn Fox Keller criticizing the primacy of the gene in the 20th century, Jerry Coyne (2000, p. 26) stated: "The supposed non-autonomy and complexity of genes lead Keller to suggest that we should replace a reductionist approach to genetics with a more holistic programme that incorporates trendy concepts such as developmental networks and self-organization. But she does not specify how this approach would work. In fact, history shows clearly that the greatest triumphs of genetics have been born of reductionism: progress nearly always comes by first studying single genes and then examining their interactions with others." In the current issue of Nature, Flack et al. (2006) attempt a non-reductionist approach to "policing" (the suppression of selfish behavior within groups: see Frank, 2003), suggesting that this category of responses (e.g., aggression, ejection of individuals from groups) "significantly contributes to maintaining stable resource networks in the face of chronic perturbations that arise through conflict" (426). Viewing group mates as potential resources to one another (via "networks"), the new paper suggests that some individuals are more successful than others in maintaining key and copious "local connections". Flack and her colleagues show that the parameters of interest to them (conflict management strategies and their influence on "multiple, overlapping social networks") significantly influence patterns of infant survivorship, aspects of cooperative behavior, and other responses.
     Of what utility might this "top down" approach be? Time will be required to "unpack" the assumptions and implications of this paper, in particular, the authors' emphasis upon "niche construction" (see Jones, 2005) which some view as a recent fad. Nonetheless, the new paper addresses an important topic not wholly resolved in ecology: What keeps groups together once they form (say, once they form in response to predation pressure)? By developing the concept that conspecifics are potential resources to one another, Flack and her associates mine these dynamic interactions in an attempt to characterize their stable (?) and perturbed (?) states, an important and intriguing exercise. These authors, however, do not treat stability in relation to individual (inclusive) fitness nor do they discuss or assess the meaning of stability relative to T (generation time), a key parameter in population biology [see Roughgarden's (1979) introduction]. Briefly, Flack et al. (2006) ignore within-group dynamics in the context of population biology and evolution, failing to discuss, for example, differential (genetic) costs and benefits to individuals and, crucially, the implications for their treatment of "local competition" (see West et al., 2002).
     The new paper is likely to generate much discussion and further studies, a worthy contribution to the literature on social complexity. It will be important to consider not only the aforementioned concerns but also the constraints on policing and other mechanisms of competition-suppression (e.g., counterstrategies such as coalitions and alliances in time and space) and the capacity to build and to sustain networks. When, for example, do individuals "go it alone"--at least for the short term, and what do time periods mean relative to T as well as an individual's reproductive value? What options do individuals have to respond to conflict relative to "effective" time periods (i.e., time periods influencing individual inclusive fitness), and when and under what conditions will individuals abort their participation in one or more social networks? Finally, it will be interesting in future to observe animal (including human) behavior for what we can learn about the (genotypic and phenotypic) costs and benefits to individuals of combining and recombining options within and between networks, social currency that may be viewed as manipulation and/or exploitation. These and other lines of investigation are likely to improve our understanding of the evolution of social behavior and, ultimately, to integrate the approach taken by Flack and her colleagues with the more conventional approaches of behavioral ecology and evolutionary biology.
* Coyne, J.A. (2000). The gene is dead; long live the gene. Nature, 408, 26-27.
* Flack, J.C., Girvan, M., de Waal, F.B.M., & Krakauer, D.C. (2006). Policing stabilizes construction of social niches in primates. Nature, 439, 426-429. [Abstract online]
* Frank, S.A. (2003). Perspective: Repression of competition and the evolution of cooperation. Evolution, 57, 693-705.
* Jones, D. (2005). Personal effects. Nature, 438, 14-16.
* Roughgarden, J. (1979). Theory of population genetics and evolutionary ecology: An introduction. New York: Macmillan.
* West, S.A., Pen, I., & Griffin, A.S. (2002). Cooperation and competition between relatives. Science, 296, 72-75.

Joan Roughgarden (JR) and colleagues have a theoretical paper in the current issue of Science titled, "Reproductive social behavior: Cooperative games to replace sexual selection". The math in this paper is not daunting; thus, the article should be accessible to anyone who is interested in JR's development of her ideas about "social selection" since the publication of her 2004 book, Evolution's rainbow: Diversity, gender, and sexuality in nature and people (see the International Society for Behavioral Ecology for a recent review [PDF]). It is not clear how the new paper will be received, and, I suspect, there is some not insignificant chance that it will be ignored. Further, it is not clear to me that JR is, in fact, saying anything new, though she may be presenting a (game) theoretical framework that has some novel features. I raise here several questions in response to her final section. Words in quotation marks are excerpted from JR's "Conclusions" (p. 968).
(1) "Reproductive social behavior and sexual reproduction are cooperative." Reproduction is "social" in the sense that social behavior is defined as interindividual interactions among conspecifics. The issue is whether mates are "cooperative"--Do mates facilitate each others' reproduction? Do mates facilitate each others' reproductive interests? When and under what circumstances do the interests of mates overlap? When and under what conditions are the optima of mates (more or less) the same?
(2) "Sexual conflict derives from negotiation breakdown." JR will need to convince Rice, Gavrilets, Holland, and others of this.
(3) "In sexual selection, sexual conflict is primitive and cooperation derived, whereas in social selection sexual cooperation is primitive and conflict derived." Well, one might say that, in evolutionary theory, including sexual selection, conflict is primitive. This and other of JR's statements can be empirically tested. Relative to this quote, it might be instructive to study taxa in which complex social traits have been lost (e.g., Parker & Rissing, 2002; Sumner et al., 2004).
(4) "Within reproductive social groups, organisms bargain and trade direct ecological benefits to maximize number of young reared." This statement bears some resemblance to "reproductive skew" theory, in particular, "incomplete control" and "tug of war" models (e.g., Clutton-Brock, 1998; Reeve et al., 1998).
(5) "Reproductive groups are coalitions of one or both sexes that may include prezygotic 'helpers'...who assist in courtship together with postzygotic helpers who assist in raising offspring." What differential individual costs and behefits obtain where asymmetries (say, in resource holding potential) obtain? What will prevent selfish individuals ("cheaters") from invading this system? When, under what conditions, and for whom do benefits of "coalitions of one or both sexes" begin to decline? What are the tradeoffs? How stable is this system (in what conditions, etc.)?
(6) "Families are reproductive groups whose participants share kinship." OK, but, under certain regimes, kin are each others' worst enemies (e.g., Perez-Tome & Toro, 1982; West et al., 2002).
(7) "Secondary sex characters are social-inclusionary traits that permit participating in the species' social system, and exclusion is reproductively lethal." Here, JR confuses SOCIAL SYSTEM with MATING SYSTEM (see Emlen & Oring, 1977). Exclusion from the mating system is "lethal" for selfish (individual, direct) reproduction; but, indirect reproduction may occur via relatives (Hamilton, 1964) as long as the individual has not been excluded from the social system(s). How are secondary sexual characters necessary for inclusion in social system (e.g., in range of non-reproductive conspecific interindividual interactions)?
(8) JR terms grooming, preening, between-sex and same-sex sexuality, etc., "coordinated team play" without considering the possibly coercive implications of these responses (Smuts & Smuts, 1993).
(9) JR terms the peacock's tail a "functionally useless badge"! This is true, in a sense. But, I wonder what peahens would have to say about JR's characterization?
(10) "In social selection theory, cooperation and team play coexist with prejudice and exclusion." This is true, as well, for natural, sexual, and group selection.
* Clutton-Brock, T.H. (1998). Reproductive skew, concessions, and limited-control. Trends in Ecology and Evolution, 13, 288-292.
* Emlen, S.T., & Oring, L.W. (1977). Ecology, sexual selection, and the evolution of mating systems. Science, 197, 215-223.
* Hamilton, W.D. (1964). The genetical evolution of social behavior (I, II). Journal of Theoretical Biology, 7, 1-52.
* Jones, C.B. (2004, Fall/Winter). A challenge worthy of the challenger? [Book review of Evolution's Rainbow (Joan Roughgarden)]. International Society for Behavioral Ecology Newsletter, 16(2), 14-16. [Link to PDF file]
* Parker, J.D., & Rissing, S.W. (2002). Molecular evidence for the origin of workerless social parasites in the ant genus Pogonomyrmex. Evolution, 56, 2017-2028.
* Perez-Tome, J.M., & Toro, M.A. (1982). Competition of similar and non-similar genotypes. Science, 299, 153-154.
* Reeve, H.K., Emlen, S.T., & Keller, L. (1998). Reproductive sharing in animal societies: Reproductive incentives or incomplete control by dominant breeders? Behavioral Ecology, 9, 267-278.
* Roughgarden, J. (2004). Evolution's rainbow: Diversity, gender, and sexuality in nature and people. Berkeley, CA: University of California Press.
* Roughgarden, J., Oishi, M., & Akcay, E. (2006). Reproductive social behavior: Cooperative games to replace sexual selection. Science, 311, 965-969.
* Smuts, B.B., & Smuts, R.W. (1993). Male aggression and sexual coercion of females in nonhuman primates and other mammals: Evidence and theoretical implications. Advances in the Study of Behavior, 22, 1-63.
* Sumner, S., Hughes, W.O.H., Pederson, J.S., & Boomsma, J. (2004). Ant parasite queens revert to mating singly. Nature, 428, 35-36.
* West, S.A., Pen, I., & Griffin, A.S. (2002). Cooperation and competition between relatives. Science, 296, 72-75.

Three new papers are of import to the TPP purpose (Melis et al., 2006; Warneken & Tomasello, 2006; Nonacs et al., 2006) and have the potential to stimulate primate, including human, research.
(1) The paper by Melis et al. (2006) is an elegant laboratory investigation of collaboration between non-kin among chimpanzees. The paper, in my view, stands on its own without need for comment except, perhaps, to gently chide the authors for making too much of conscious and aware processes and for not making enough of the study's implications for the evolution of self-interest (i.e., chimpanzees discriminate between competent and less competent partners).
(2) Warneken & Tomasello (2006) conducted a study of helping behavior by human infants and young chimpanzees. In both conditions, the young organisms help a human adult. This paper is laden with terminology of which many students of primates are very fond ("altruistic helping", "motivation", "cognitive", "goals") in addition to untested claims of human uniqueness. A major problem with this study is the inherent asymmetry in resource holding potential, fighting ability, and/or "power" between the immature individuals ("altruists" read "dependents" or "victims") and their adult partners (read, "despots"). The authors' findings of compliance and/or acquiescence by the immatures are more likely to represent avoidance of (potential) aggression, punishment, social parasitism, manipulation, etc. than "altruistic helping". Related to this, rather than demonstrating preadaptations for altruism in chimps and humans, might the results of Warneken & Tomasello's (2006) study demonstrate preadaptation for social learning and/or imitation? Indeed, social learning and/or imitation may have evolved initially as mechanisms to avoid punishment (e.g., aggression, phenotypic manipulation, etc.). In an article published 6 March in The Boston Globe, Warneken is quoted as saying: "You have to be motivated to act on behalf of the other, not your own goals." It genuinely saddens me to acknowledge that the findings of behavioral ecology have not, for the most part, penetrated primatology: cooperation and altruism ARE selfish in the sense that, relative to certain environmental regimes (abiotic and biotic, including social), cooperation and/or altruism may yield the highest benefits to the actor (among those options available and perceived). Indeed, it is likely that cooperation and altruism represent "best of a bad job" responses likely to have been favored in the heterogeneous regimes characteristic of human (and many other primate) evolution. These arguments will apply, as well, to other social mammals.
(3) Nonacs and his colleagues (2006), studying wasps, address the evolution of subordinance, showing that cooperation and/or altruism may occur without high skew and high coefficients of relatedness (r). Exploring these conditions theoretically, these authors address alternative explanations for the results summarized in their review of the literature. These authors' findings may not be surprising since it seems likely that cooperation and/or altruism may evolve wherever there is some likelihood that conspecifics may share some (threshold) proportion of one's genes (e.g., in "neighborhoods"). This idea could be tested by measuring whether the likelihood of helping decreases with increasing distance from a natal source. As stated above, cooperation and altruism are likely to be "best of a bad job" responses and may be temporary as well as permanent, a possibility generally not tested. Again, like the comments above, the results discussed by Nonacs et al. might be explained by avoidance of punishment or by "involuntary altruism" and/or social parasitism (parasitism of subordinates by dominants), including phenotypic manipulation.
* Melis, A.P., Hare, B., & Tomasello, M. (2006). Chimpanzees recruit the best collaborators. Science, 311, 1297-1300 (DOI: 10.1126/science.1123007). [Abstract online]
* Nonacs, P., Liebert, A.E., & Starks, P.T. (2006). Transactional skew and assured fitness return models fail to predict patterns of cooperation in wasps. American Naturalist, 167, 000-000. [Abstract online]
* Warneken, F., & Tomasello, M. (2006). Altruistic helping in human infants and young chimpanzees. Science, 311, 1301-1303 (DOI: 10.1126/science.1121448). [Abstract online]

I read with interest Joan Herbers' article in the 24 March 2006 Chronicle of Higher Education titled, "The loaded language of science". Herbers, a professor of evolution, ecology, and organismal biology at Ohio State University, calls for substituting the term "pirate" for "slavemaking" in studies of social parasitism, particularly in ants. According to Herbers, the term "slavemaking" is an inaccurate analogy between the observed social parasitism and human slavery and may be socially offensive. Certainly scientific terminology, like language in general, may lend itself to multiple interpretations, possibly socially laden. While scientists are, of course, free to use any terminology they wish to describe their own investigations and while the "pirate" metaphor has utility for describing some socially parasitic responses, I think that it is not a good metaphor to substitute for what we mean when we use "slavemaking" or "dulosis" since pirates do not appropriate the "work" of their victims (i.e., hosts). Further, Herbers states that "captive worker ants cannot breed", using this observation for evidence against the appropriateness of "slavemaking" as an analogy to human behavior. Yet, many (male) slaves were, indeed, castrated, and the offspring of slaves were, themselves, intended to serve their slavemasters (social parasites) as victims/slaves/hosts. The fundamental similarity between slavemaking in social insects and slavemaking in humans, in my opinion, is the social parasite's appropriation of the host's (the victim's) energy and time (labor/resources) for selfish allocation by slavemasters.
     Social parasitism in primates, including humans, has been addressed in several publications (e.g., Jones, 2005a, b) and it has been proposed that kidnapping in non-human primates may be ancestral to "slavemaking" in humans (Jones, 2005b). Kidnapping and adoption may be derived from "allomothering"/"alloparenting" behavior(s).
* Herbers, J. (2006, 24 March). The loaded language of science. Retrieved 24 March 2006 from <http://chronicle.com>.
* Jones, C.B. (2005a). Behavioral flexibility in primates: Causes and consequences. New York: Springer.
* Jones, C.B. (2005b). Social parasitism in mammals with particular reference to Neotropical primates. Mastozoologia Neotropical, 12(1), 19-35. [Full text online as PDF file]
Addendum
An investigation of the evolution of slavemaking in primates will entail the use of comparative (phylogenetic) methods. I am currently collaborating with Patrik Lindenfors [home page] to test the idea that the evolution of (1) Maternal Care----> (is ancestral to) (2) Alloparenting/Allomothering (Helping)----> (3) Adoption----> (4) Kidnapping----> (5) Slavemaking. Each of these might be relatively short-term or relatively long-term relative to generation time (T). It is not clear at this time which, if any, stages might be skipped evolutionarily (e.g., can "maternal care" proceed directly, evolutionarily, to "kidnapping"). We will keep subscribers informed of our results.




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