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Results for “Evolution of cooperation”

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At least 397 records · Page 22Linked to original sources
PubMed2001

Why people punish defectors. Weak conformist transmission can stabilize costly enforcement of norms in cooperative dilemmas.

In this paper, we present a cultural evolutionary model in which norms for cooperation and punishment are acquired via two cognitive mechanisms: (1) payoff-biased transmission-a tendency to copy the most successful individual; and (2) conformist transmission-a tendency to copy the most frequent behavior in the population. We first show that if a finite number of punishment stages is permitted (e.g. two stages of punishment occur if some individuals punish people who fail to punish non-cooperators), then an arbitrarily small amount of conformist transmission will stabilize cooperative behavior by stabilizing punishment at some n -th stage. We then explain how, once cooperation is stabilized in one group, it may spread through a multi-group population via cultural group selection. Finally, once cooperation is prevalent, we show how prosocial genes favoring cooperation and punishment may invade in the wake of cultural group selection.

Cooperative Behavior↗
PubMed2003

Reputation and the evolution of conflict.

The outcomes of conflicts in many human societies generate reputation effects that influence the nature of later conflicts. Those willing to escalate over even trivial offenses are considered honorable whereas those who do not are considered dishonorable (Nisbett & Cohen, 1996). Here I extend Maynard Smith's hawk-dove model of animal conflict to explore the logic of a strategy which uses reputation about its opponents to regulate its behavior. I show that a reputation-based strategy does well when (1) the value of the resource is large relative to the cost of losing a fight, (2) communities are stable, and (3) reputations are well known but subject to some amount of error. Reputation-based strategies may thus result in greater willingness to fight, but less fighting at equilibrium, depending upon the nature of the contests and the local socioecology. Additionally, this strategy is robust in the presence of poor knowledge about reputation.

Animals↗
PubMed2005

The foraging gene, behavioral plasticity, and honeybee division of labor.

In recent years, the honeybee has emerged as an excellent model for molecular and genetic studies of complex social behaviors. By using the global gene expression methods as well as the candidate gene approach, it is now possible to link the function of genes to social behaviors. In this paper, I discuss the findings about one such gene, foraging, a cGMP-dependent protein kinase. The involvement of this gene in regulating division of labor is discussed on two independent, but not mutually exclusive levels; the possible mechanisms for PKG action in regulating behavioral transitions associated with honeybee division of labor, and its possible involvement in the evolution of division of labor in bees.

Adaptation, Physiological↗
PubMed2004

Evolution of mutualism through spatial effects.

Mutualism among species is ubiquitous in natural ecosystems but its evolution is not well understood. We provided a simple lattice model to clarify the importance of spatial structure for the evolution of mutualism. We assumed reproductive rates of two species are modified through interaction between species and examine conditions where mutualists of both species, that give some benefit to the other species with their own cost, invade non-mutualists populations. When dispersal of offspring is unlimited, we verified the evolution of mutualism is impossible under any condition. On the other hand, when the dispersal is limited to neighboring lattice sites, mutualists can invade if the ratio of cost to benefit is low and the intrinsic reproductive rate is low in case where the parameter values are symmetric between species. Under the same conditions, non-mutualists cannot invade mutualist populations, that is, the latter are evolutionarily stable. In case of asymmetric parameters, mutualists tend to invade if the average value of costs to two species is low or that of benefits is high, and if the intrinsic reproductive rate is low for one of the two species. A mechanistic explanation of why mutualists increase when the dispersal is limited is given by showing that mutualist pairs of the two species at the same lattice site rapidly increase at the initial phase of the invasion.

Altruism↗
PubMed2005

Properties of a mixed ESS candidate in continuous strategy sets.

An evolutionarily stable strategy (ESS) is a strategy that if almost all members of the population adopt, then this population cannot be invaded by any mutant strategy. An ESS is not necessarily a possible end point of the evolutionary process. Moreover, there are cases where the population evolves towards a strategy that is not an ESS. This paper studies the properties of a unique mixed ESS candidate in a continuous time animal conflict. A member of a group sized three finds itself at risk and needs the assistance of another group member to be saved. In this conflict, a player's strategy is to choose the probability distribution of the interval between the beginning of the game and the moment it assists the player which is at risk. We first assume that a player is only allowed to choose an exponential distribution, and show that in this case the ESS candidate is an attracting ESS; the population will always evolve towards this strategy, and once it is adopted by most members of the population it cannot be invaded by mutant strategies. Then, we extend the strategy sets and allow a player to choose any continuous distribution. We show that although this ESS candidate may no longer be an ESS, under fairly general conditions the population will tend towards it. This is done by characterizing types of strategies that if established in the population, can be invaded by this ESS candidate, and by presenting possible paths of transition from other types of common strategies to this ESS candidate.

Animals↗
PubMed2006

The evolution of altruism: game theory in multilevel selection and inclusive fitness.

Although the prisoner's dilemma (PD) has been used extensively to study reciprocal altruism, here we show that the n-player prisoner's dilemma (NPD) is also central to two other prominent theories of the evolution of altruism: inclusive fitness and multilevel selection. An NPD model captures the essential factors for the evolution of altruism directly in its parameters and integrates important aspects of these two theories such as Hamilton's rule, Simpson's paradox, and the Price covariance equation. The model also suggests a simple interpretation of the Price selection decomposition and an alternative decomposition that is symmetrical and complementary to it. In some situations this alternative shows the temporal changes in within- and between-group selection more clearly than the Price equation. In addition, we provide a new perspective on strong vs. weak altruism by identifying their different underlying game structures (based on absolute fitness) and showing how their evolutionary dynamics are nevertheless similar under selection (based on relative fitness). In contrast to conventional wisdom, the model shows that both strong and weak altruism can evolve in periodically formed random groups of non-conditional strategies if groups are multigenerational. An integrative approach based on the NPD helps unify different perspectives on the evolution of altruism.

Altruism↗
PubMed2004

[Management of delivery in patients with Marfan's syndrome presenting aortic dilatation].

OBJECTIVE: We report the anesthesic and obstetrical management of two pregnant patients with Marfan's syndrome. An important dilatation of the root of aorta was established at the beginning of the pregnancy. Based on a review of the literature and our experience, we searched for clues to identify the ideal term and the best mode of delivery, and which type of anesthesia may be the more appropriate in patients with aortic dilatation. RESULTS: No consensus can be found in the literature as far as anesthesia and obstetric management of these patients is concerned. Pregnancy must be continued as long as possible to ensure adequate fetal growth but fetal extraction should not be delayed if the diameter of the aorta enlarges too much. A diameter of 40 mm is probably the higher limit to accept for vaginal delivery. Beyond, cautious cesarean section would be advisable. In the absence of dural ectasia or a technical problem, neuraxial anesthesia is a good option. CONCLUSION: According to the severity of the aortic dilatation and its evolution, specific management, based on good cooperation between obstetricians and anesthesiologists, is the key of a successful and safe childbirth.

Adult↗
PubMed2002

Primer: altruism.

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Altruism↗
PubMed2003

Extreme reversed sexual size dimorphism in the extinct New Zealand moa Dinornis.

The ratite moa (Aves; Dinornithiformes) were massive graviportal browsers weighing up to 250 kg (ref. 1) that dominated the New Zealand biota until their extinction approximately 500 yr ago. Despite an extensive Quaternary fossil record, moa taxonomy remains problematic and currently 11 species are recognized. Three Dinornis species were found throughout New Zealand and differed markedly in size (1-2 m height at back) and mass (from approximately 34 to 242 kg). Surprisingly, ancient mitochondrial DNA sequences show that the three species were genetically indistinguishable within each island, but formed separate North and South Island clades. Here we show, using the first sex-linked nuclear sequences from an extinct species, that on each island the three morphological forms actually represent just one species, whose size varied markedly according to sex and habitat. The largest females in this example of extreme reversed sexual size dimorphism were about 280% the weight and 150% the height of the largest males, which is unprecedented among birds and terrestrial mammals. The combination of molecular and palaeontological data highlights the difficulties of analysing extinct groups, even those with detailed fossil records.

Animals↗
PubMedDate not supplied

The recovery of trust.

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Biological Evolution↗