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PubMed2003

Monkeys reject unequal pay.

During the evolution of cooperation it may have become critical for individuals to compare their own efforts and pay-offs with those of others. Negative reactions may occur when expectations are violated. One theory proposes that aversion to inequity can explain human cooperation within the bounds of the rational choice model, and may in fact be more inclusive than previous explanations. Although there exists substantial cultural variation in its particulars, this 'sense of fairness' is probably a human universal that has been shown to prevail in a wide variety of circumstances. However, we are not the only cooperative animals, hence inequity aversion may not be uniquely human. Many highly cooperative nonhuman species seem guided by a set of expectations about the outcome of cooperation and the division of resources. Here we demonstrate that a nonhuman primate, the brown capuchin monkey (Cebus apella), responds negatively to unequal reward distribution in exchanges with a human experimenter. Monkeys refused to participate if they witnessed a conspecific obtain a more attractive reward for equal effort, an effect amplified if the partner received such a reward without any effort at all. These reactions support an early evolutionary origin of inequity aversion.

Aging↗
PubMed2006

Altruism through beard chromodynamics.

The evolution of altruism, a behaviour that benefits others at one's own fitness expense, poses a darwinian paradox. The paradox is resolved if many interactions are with related individuals so that the benefits of altruism are reaped by copies of the altruistic gene in other individuals, a mechanism called kin selection. However, recognition of altruists could provide an alternative route towards the evolution of altruism. Arguably the simplest recognition system is a conspicuous, heritable tag, such as a green beard. Despite the fact that such genes have been reported, the 'green beard effect' has often been dismissed because it is unlikely that a single gene can code for altruism and a recognizable tag. Here we model the green beard effect and find that if recognition and altruism are always inherited together, the dynamics are highly unstable, leading to the loss of altruism. In contrast, if the effect is caused by loosely coupled separate genes, altruism is facilitated through beard chromodynamics in which many beard colours co-occur. This allows altruism to persist even in weakly structured populations and implies that the green beard effect, in the form of a fluid association of altruistic traits with a recognition tag, can be much more prevalent than hitherto assumed.

Altruism↗
PubMed1989

Familiar neighbors enhance breeding success in birds.

We tested the hypothesis that long-term familiarity with neighbors is advantageous by determining whether male red-winged blackbirds (Agelaius phoeniceus) breeding adjacent to familiar neighbors have better reproductive success than other males. Using data gathered during a 10-yr study of breeding success, we found that males with familiar neighbors fledged, on average, significantly more offspring annually than males without familiar neighbors. We also found that the same males, breeding in different years on the same territories, had significantly larger harems in the years they had familiar neighbors. Improved reproductive success was due to the males' abilities to attract more females to nest in their territories. Alternative hypotheses to explain the positive relationship between familiar neighbors and breeding success were not supported by our data. Relatively high reproductive success for breeders with long-term neighbors may provide a basis for the evolution of cooperative behavior in this and other species.

Animals↗
PubMed1990

DNA "fingerprinting" reveals high levels of inbreeding in colonies of the eusocial naked mole-rat.

Using the technique of DNA fingerprinting, we investigated the genetic structure within and among four wild-caught colonies (n = 50 individuals) of a eusocial mammal, the naked mole-rat (Heterocephalus glaber; Rodentia: Bathyergidae). We found that DNA fingerprints of colony-mates were strikingly similar and that between colonies they were much more alike than fingerprints of non-kin in other free-living vertebrates. Extreme genetic similarity within colonies is due to close genetic relationship (mean relatedness estimate +/- SE, r = 0.81 +/- 0.10), which apparently results from consanguineous mating. The inbreeding coefficient (F = 0.45 +/- 0.18) is the highest yet recorded among wild mammals. The genetic structure of naked mole-rat colonies lends support to kin selection and ecological constraints models for the evolution of cooperative breeding and eusociality.

Animals↗
PubMed1998

Relatedness of matrilines, dispersing males and social groups in long-tailed macaques (Macaca fascicularis).

Genealogical relatedness is thought to be an important causal factor in the evolution of cooperation. We inferred relatedness on the basis of 11 blood protein markers using the Queller and Goodnight index of relatedness in a macaque population with long-term demographic records. This estimate reflected independently determined pedigree relationships in our data set. Mean relatedness among all members of a social group was 0.10 but much higher levels of relatedness (0.30-0.47) were found among the members of matrilineal families with a high or intermediate social rank. Groups of dispersing males that had been born into the same social group were sometimes closely related (0.43 and 0.58), but they could also be less related (0.08). We found that the pattern of distribution of relatedness was associated with gene flow and differential reproduction in males, rather than with group fission and the presence of geographical barriers.

Animals↗
PubMed2001

Spatial Ultimatum Games, collaborations and the evolution of fairness.

It is often the case that individuals in a social group can perform certain tasks (such as hunting, for example) more efficiently if they collaborate with other individuals than if they act alone. In such situations one is necessarily faced with the problem of how the resource obtained as the result of such a collaboration should be divided among the collaborating individuals. If one of the individuals in the collaboration is in a position (through its dominance rank, for example) to impose a particular division of the resource on the other members of the collaboration then we show that an evolutionary dilemma arises which prevents such collaborations being evolutionarily stable. This dilemma, which is closely related to the well-known Ultimatum Game, results from the fact that in such situations natural selection favours individuals who, if dominant, offer smaller and smaller shares of the resource to the others and, if subdominant, will accept lower and lower offers. We also show, however, that this dilemma is naturally resolved in a spatially structured population with selection favouring the evolution of a fair division of the resource and consequently ensuring the evolutionary stability of collaborations of this type.

Animals↗
PubMed2003

Contrasting relatedness patterns in bottlenose dolphins (Tursiops sp.) with different alliance strategies.

Male bottlenose dolphins (Tursiops sp.) in Shark Bay have one of the most complex male societies outside humans. Two broad mating strategies have been identified in males. In the first strategy, there are two types of alliances: stable 'first-order' pairs and trios that herd individual females in reproductive condition, and 'second-order' teams of two first-order alliances (five or six individuals) that join forces against rivals in contests for females. In the alternative strategy, a 'super-alliance' of ca. 14 individuals, males form pairs or trios to herd females, but in contrast to the stable alliances, these pairs and trios are highly labile. Here, we show that males in stable first-order alliances and the derived second-order alliances are often strongly related, so that they may gain inclusive fitness benefits from alliance membership. By contrast, members of the super-alliance are no more closely related than expected by chance. Further, the strength of the association of alliance partners within the super-alliance, as measured by an index of joint participation in consorting a female, was not correlated with their genetic relatedness. Thus, within one population and one sex, it appears that there may be simultaneous operation of more than one mode of group formation.

Animals↗
PubMed2005

Relatedness and helping in fish: examining the theoretical predictions.

Many studies have attempted to explain the evolution of cooperation, yet little attention has been paid to what factors control the amount or kind of cooperation performed. Kin selection theory suggests that more cooperation, or help, should be given by relatives. However, recent theory suggests that under specific ecological and demographic conditions, unrelated individuals must 'pay to stay' in the group and therefore may help more. We tested these contrasting predictions using the cooperatively breeding fish, Neolamprologus pulcher, and found that the degree of work effort by helpers depended on which helping behaviours were considered and on their level of relatedness to the breeding male or female. In the field, helpers unrelated to the breeding male performed more territory defence, while helpers unrelated to the breeding female contributed less to territory defence. In the laboratory, unrelated group members helped more. Our work demonstrates that a number of factors in addition to kinship shape cooperative investment patterns.

Animals↗
PubMed2006

Facing the facts.

Explore the source record for details and available documents.

Altruism↗
PubMed1976

Social behavior of the conilurine rodents (Muridae) of Australia.

This paper describes in detail the elements of social behaviour and social organizations of four closely related rodents (Notomys alexis, Pseudomys albocinereus, P. shortridgei and P. desertor) from diverse habitats, and the social organizations of seven other conilurine rodents are described briefly. Most of the data were determined from quantitative observations of animals caged in twos or in larger groups for at least ten days. Breeding pairs were observed daily throughout pregnancy and parenthood. A dispersed organization and three types of communal organization are described, and evolutionary trends in dispersion and territoriality, cohesion, communication and co-operation are discussed.

Agonistic Behavior↗