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PubMed2006

Reliance on head versus eyes in the gaze following of great apes and human infants: the cooperative eye hypothesis.

As compared with other primates, humans have especially visible eyes (e.g., white sclera). One hypothesis is that this feature of human eyes evolved to make it easier for conspecifics to follow an individual's gaze direction in close-range joint attentional and communicative interactions, which would seem to imply especially cooperative (mututalistic) conspecifics. In the current study, we tested one aspect of this cooperative eye hypothesis by comparing the gaze following behavior of great apes to that of human infants. A human experimenter "looked" to the ceiling either with his eyes only, head only (eyes closed), both head and eyes, or neither. Great apes followed gaze to the ceiling based mainly on the human's head direction (although eye direction played some role as well). In contrast, human infants relied almost exclusively on eye direction in these same situations. These results demonstrate that humans are especially reliant on eyes in gaze following situations, and thus, suggest that eyes evolved a new social function in human evolution, most likely to support cooperative (mututalistic) social interactions.

Animals↗
PubMed2006

Genetic stability and territorial structure facilitate the evolution of tag-mediated altruism.

Evolutionary theorists have long been interested in the conditions that permit the evolution of altruistic cooperation. Recent work has demonstrated that altruistic donation can evolve in surprisingly simple models, in which agents base their decisions to donate solely on the similarity of evolved "tags" relative to evolved tag-difference tolerances. There is disagreement, however, about the conditions under which tag-mediated altruism will in fact evolve. Here we vary two critical parameters in a standard model of tag-mediated altruism-genetic stability and territorial structure-and show that altruism evolves in a wide range of conditions. We demonstrate the evolution of significant levels of altruism even when the immediate costs to donors equal the benefits to recipients. We describe the mechanism that permits the emergence of altruism in the model as a form of kin selection that is facilitated by interactions between altruism, genetic drift, and fecundity.

Altruism↗
PubMed2006

Interspecific communicative and coordinated hunting between groupers and giant moray eels in the Red Sea.

Intraspecific group hunting has received considerable attention because of the close links between cooperative behaviour and its cognitive demands. Accordingly, comparisons between species have focused on behaviours that can potentially distinguish between the different levels of cognitive complexity involved, such as "intentional" communication between partners in order to initiate a joint hunt, the adoption of different roles during a joint hunt (whether consistently or alternately), and the level of food sharing following a successful hunt. Here we report field observations from the Red Sea on the highly coordinated and communicative interspecific hunting between the grouper, Plectropomus pessuliferus, and the giant moray eel, Gymnothorax javanicus. We provide evidence of the following: (1) associations are nonrandom, (2) groupers signal to moray eels in order to initiate joint searching and recruit moray eels to prey hiding places, (3) signalling is dependent on grouper hunger level, and (4) both partners benefit from the association. The benefits of joint hunting appear to be due to complementary hunting skills, reflecting the evolved strategies of each species, rather than individual role specialisation during joint hunts. In addition, the partner species that catches a prey item swallows it whole immediately, making aggressive monopolisation of a carcass impossible. We propose that the potential for monopolisation of carcasses by one partner species represents the main constraint on the evolution of interspecific cooperative hunting for most potentially suitable predator combinations.

Animal Communication↗
PubMed2006

Parochial altruism in humans.

Social norms and the associated altruistic behaviours are decisive for the evolution of human cooperation and the maintenance of social order, and they affect family life, politics and economic interactions. However, as altruistic norm compliance and norm enforcement often emerge in the context of inter-group conflicts, they are likely to be shaped by parochialism--a preference for favouring the members of one's ethnic, racial or language group. We have conducted punishment experiments, which allow 'impartial' observers to punish norm violators, with indigenous groups in Papua New Guinea. Here we show that these experiments confirm the prediction of parochialism. We found that punishers protect ingroup victims--who suffer from a norm violation--much more than they do outgroup victims, regardless of the norm violator's group affiliation. Norm violators also expect that punishers will be lenient if the latter belong to their social group. As a consequence, norm violations occur more often if the punisher and the norm violator belong to the same group. Our results are puzzling for evolutionary multi-level selection theories based on selective group extinction as well as for theories of individual selection; they also indicate the need to explicitly examine the interactions between individuals stemming from different groups in evolutionary models.

Adolescent↗
PubMed2006

Evolutionary games and population dynamics: maintenance of cooperation in public goods games.

The emergence and abundance of cooperation in nature poses a tenacious and challenging puzzle to evolutionary biology. Cooperative behaviour seems to contradict Darwinian evolution because altruistic individuals increase the fitness of other members of the population at a cost to themselves. Thus, in the absence of supporting mechanisms, cooperation should decrease and vanish, as predicted by classical models for cooperation in evolutionary game theory, such as the Prisoner's Dilemma and public goods games. Traditional approaches to studying the problem of cooperation assume constant population sizes and thus neglect the ecology of the interacting individuals. Here, we incorporate ecological dynamics into evolutionary games and reveal a new mechanism for maintaining cooperation. In public goods games, cooperation can gain a foothold if the population density depends on the average population payoff. Decreasing population densities, due to defection leading to small payoffs, results in smaller interaction group sizes in which cooperation can be favoured. This feedback between ecological dynamics and game dynamics can generate stable coexistence of cooperators and defectors in public goods games. However, this mechanism fails for pairwise Prisoner's Dilemma interactions and the population is driven to extinction. Our model represents natural extension of replicator dynamics to populations of varying densities.

Animals↗
PubMed1998

Transcriptional control of Drosophila bicoid by Serendipity delta: cooperative binding sites, promoter context, and co-evolution.

Concentration of maternal BICOID (BCD) establishes the anterior pattern in the Drosophila embryo. Successive deletions in the bcd promoter allowed us to localize an enhancer sequence in the 5'-UTR and a down-regulating element downstream of the ATG initiator codon, and identify a 49 bp region sufficient to drive transcription of a reporter gene specifically in nurse cells. This fragment contains two binding sites for the Serendipity (Sry) d zinc finger activator, that mediate its cooperative binding. Both sites (sdbs) are essential for bcd expression. Further analysis showed that the bcd promoter configuration is decisive for Sry d activating function. Replacement of sdbs by binding sites for Sry b, the Sry d paralog, restores bcd transcription in sry d mutant ovaries, demonstrating that the functional divergence between these two proteins during evolution was mainly driven by changes in their DNA-specific recognition properties, resulting in the control of separate developmental pathways.

Animals↗
PubMed2005

Experimental evolution of conflict mediation between genomes.

Transitions to new levels of biological complexity often require cooperation among component individuals, but individual selection among those components may favor a selfishness that thwarts the evolution of cooperation. Biological systems with elements of cooperation and conflict are especially challenging to understand because the very direction of evolution is indeterminate and cannot be predicted without knowing which types of selfish mutations and interactions can arise. Here, we investigated the evolution of two bacteriophages (f1 and IKe) experimentally forced to obey a life cycle with elements of cooperation and conflict, whose outcome could have ranged from extinction of the population (due to selection of selfish elements) to extreme cooperation. Our results show the de novo evolution of a conflict mediation system that facilitates cooperation. Specifically, the two phages evolved to copackage their genomes into one protein coat, ensuring cotransmission with each other and virtually eliminating conflict. Thereafter, IKe evolved such extreme genome reduction that it lost the ability to make its own virions independent of f1. Our results parallel a variety of conflict mediation mechanisms existing in nature: evolution of reduced genomes in symbionts, cotransmission of partners, and obligate coexistence between cooperating species.

Bacteriophages↗
PubMed1999

Mutational analysis of the affinity maturation of antibody 48G7.

The affinity maturation of antibody 48G7 from its germline predecessor 48G7g has been studied at a molecular level through a combination of structural and biochemical means. Each of the nine somatic mutations accumulated during affinity maturation has been assessed for gain or loss of function in both the germline and affinity-matured antibodies. Individual somatic mutations were found to be either positive or neutral in their effects on affinity for hapten JWJ1, with a marked context-dependence for some sites of mutation. In a number of cases significant cooperativity was found between pairs of somatically mutated residues. Interpretation of the structural changes introduced by many of the point mutations has been possible due to the availability of high-resolution crystal structures of 48G7g and 48G7, and mechanisms by which these structural changes may result in enhanced affinity for hapten have been identified. Precise dissection of structure-function relationships in this system provides additional insights into the role of cooperativity in the evolution of antibody affinity. Comparison of 48G7 with previously characterized systems provides a varied view of the structure-function mechanisms by which the humoral immune system produces large increases in affinity.

Animals↗
PubMedDate not supplied

Energy intake during reproduction in captive common marmosets (Callithrix jacchus).

Among haplorhine primates, the highly specialized Callitrichidae (marmosets and tamarins) are expected to have comparatively high reproductive costs, a feature that might be related to the evolution of a cooperative breeding system. Costs of reproduction in captivity were investigated on the basis of changes in energy intake and body weight during pregnancy and lactation in pair-living female and male common marmosets (Callithrix jacchus). The experimental design had little effect on carrying behavior, food intake, and body weight of adults, but a negative transitory effect of offspring body weight. Increased energetic requirements during pregnancy did not result in a higher energy intake in females. During lactation, females increased their energy intake up to 100% and gradually lost weight, suggesting even higher costs. Extensive carrying behavior by males, on the other hand, did not result in an increased energy intake in males, or in changes in male body weight. It is suggested that, at least in captivity, increased energetic demands during reproduction are reduced by behavior allocations towards energetically less expensive behaviors.

Aging↗
PubMedDate not supplied

The socioeconomic significance of nature-based recreation in Canada.

In recognition of the many values that people ascribe to nature, federal, provincial, and territorial agencies worked in partnership to complete the 'Survey on the Importance of Nature to Canadians' (SINC) in 1981, 1987, 1991, and 1996. Between 1981 and 1996, more than 80% of Canadians 15 years of age and older engaged in one or more nature-related activities. This paper describes the evolution of this cooperative monitoring program, defines a classification system as a context for the values examined by the SINC, highlights trends of some nature-related recreational activities measured by the survey, and comments on the importance of this information to Canadians.

Animals↗
PubMed2002

Scale-invariant behavior in a spatial game of prisoners' dilemma.

A spatially extended version of the game of prisoner's dilemma, originally proposed by Nowak and May, is modified to include stochastic updating and found to exhibit scale-invariant behavior. Two critical regimes with different scaling behaviors are found; the corresponding exponents have been determined numerically. Spatially, the critical states are characterized by the existence of delicately balanced networks of defectors separating domains of cooperators; temporally, the evolution of the critical states following local perturbations is characterized by avalanches of various magnitudes, which cause restructuring of the networks of defectors on all scales.

Journal Article↗
PubMed2004

The neural basis of altruistic punishment.

Many people voluntarily incur costs to punish violations of social norms. Evolutionary models and empirical evidence indicate that such altruistic punishment has been a decisive force in the evolution of human cooperation. We used H2 15O positron emission tomography to examine the neural basis for altruistic punishment of defectors in an economic exchange. Subjects could punish defection either symbolically or effectively. Symbolic punishment did not reduce the defector's economic payoff, whereas effective punishment did reduce the payoff. We scanned the subjects' brains while they learned about the defector's abuse of trust and determined the punishment. Effective punishment, as compared with symbolic punishment, activated the dorsal striatum, which has been implicated in the processing of rewards that accrue as a result of goal-directed actions. Moreover, subjects with stronger activations in the dorsal striatum were willing to incur greater costs in order to punish. Our findings support the hypothesis that people derive satisfaction from punishing norm violations and that the activation in the dorsal striatum reflects the anticipated satisfaction from punishing defectors.

Adult↗
PubMed1998

The ecology and behavior of burying beetles.

Burying beetles conceal small vertebrate carcasses underground and prepare them for consumption by their young. This review places their complex social behavior in an ecological context that focuses on the evolution of biparental care and communal breeding. Both males and females provide extensive parental care, and the major benefit of male assistance is to help defend the brood and carcass from competitors. As intensity and type of competition vary, so do the effectiveness and duration of male care. In many species, a single brood may be reared on large carcasses by more than one male and/or female. Limited reproductive opportunities, the greater effectiveness of groups in preventing the probability of brood failure (especially that caused by competing flies), and the superabundance of food on large carcasses have contributed to the evolution of this cooperative behavior.

Journal Article↗
PubMed2003

Functional cooperation between exonucleases and endonucleases--basis for the evolution of restriction enzymes.

Many types of restriction enzymes cleave DNA away from their recognition site. Using the type III restriction enzyme, EcoP15I, which cleaves DNA 25-27 bp away from its recognition site, we provide evidence to show that an intact recognition site on the cleaved DNA sequesters the restriction enzyme and decreases the effective concentration of the enzyme. EcoP15I restriction enzyme is shown here to perform only a single round of DNA cleavage. Significantly, we show that an exonuclease activity is essential for EcoP15I restriction enzyme to perform multiple rounds of DNA cleavage. This observation may hold true for all restriction enzymes cleaving DNA sufficiently far away from their recognition site. Our results highlight the importance of functional cooperation in the modulation of enzyme activity. Based on results presented here and other data on well-characterised restriction enzymes, a functional evolutionary hierarchy of restriction enzymes is discussed.

Binding Sites↗
PubMed1976

[International strategies in medical education: technical assistance and technical cooperation].

This article reviews the evolution of international activity for national development in general and for medical education in particular. The concepts of traditional technical aid and the new method of technical cooperation are studied. That method appeared just before the beginning of this decade as a response to needs existing at the time to coordinate development with the emerging international economic order. This article discusses the emphasis given to strategy in this new concept of international activity. Strategy, in this sense, consists of a clear definition of goals and objectives by the countries themselves, mobilization of local resources, and full participation of national personnel in all phases of the process. The projects promoted by the Pan American Health Organization in applying technical cooperation to the field of health manpower training are discussed. Such activities include: coordinating the above mentioned training, providing overall support for institutional development, training professors and administrators, developing educational technology, creating and developing a network of biomedical information, developing social sciences as applied to medicine, and encouraging medical, epidemiological, social, and operational research.

Education, Medical↗
PubMed2007

What can microbial genetics teach sociobiology?

Progress in our understanding of sociobiology has occurred with little knowledge of the genetic mechanisms that underlie social traits. However, several recent studies have described microbial genes that affect social traits, thereby bringing genetics to sociobiology. A key finding is that simple genetic changes can have marked social consequences, and mutations that affect cheating and recognition behaviors have been discovered. The study of these mutants confirms a central theoretical prediction of social evolution: that genetic relatedness promotes cooperation. Microbial genetics also provides an important new perspective: that the genome-to-phenome mapping of social organisms might be organized to constrain the evolution of social cheaters. This constraint can occur both through pleiotropic genes that link cheating to a personal cost and through the existence of phoenix genes, which rescue cooperative systems from selfish and destructive strategies. These new insights show the power of studying microorganisms to improve our understanding of the evolution of cooperation.

Animals↗
PubMed2007

Negotiation of mutualism: rhizobia and legumes.

The evolution and persistence of biological cooperation have been an important puzzle in evolutionary theory. Here, we suggest a new approach based on bargaining theory to tackle the question. We present a mechanistic model for negotiation of benefits between a nitrogen-fixing nodule and a legume plant. To that end, we first derive growth rates for the nodule and plant from metabolic models of each as a function of material fluxes between them. We use these growth rates as pay-off functions in the negotiation process, which is analogous to collective bargaining between a firm and a workers' union. Our model predicts that negotiations lead to the Nash bargaining solution, maximizing the product of players' pay-offs. This work introduces elements of cooperative game theory into the field of mutualistic interactions. In the discussion of the paper, we argue for the benefits of such an approach in studying the question of biological cooperation.

Biological Evolution↗