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PubMed2004

Conditional use of sex and parthenogenesis for worker and queen production in ants.

The near-ubiquity of sexual reproduction in animal species has long been considered a paradox because sexually reproducing individuals transmit only half of their genome to their progeny. Here, we show that the ant Cataglyphis cursor circumvents this cost by using alternative modes of reproduction for the production of reproductive and nonreproductive offspring. New queens are almost exclusively produced by parthenogenesis, whereas workers are produced by normal sexual reproduction. By selectively using sex for somatic growth and parthenogenesis for germline production, C. cursor has taken advantage of the ant caste system to benefit from the advantages of both sexual and asexual reproduction.

Alleles↗
PubMed2006

Chimpanzees recruit the best collaborators.

Humans collaborate with non-kin in special ways, but the evolutionary foundations of these collaborative skills remain unclear. We presented chimpanzees with collaboration problems in which they had to decide when to recruit a partner and which potential partner to recruit. In an initial study, individuals recruited a collaborator only when solving the problem required collaboration. In a second study, individuals recruited the more effective of two partners on the basis of their experience with each of them on a previous day. Therefore, recognizing when collaboration is necessary and determining who is the best collaborative partner are skills shared by both chimpanzees and humans, so such skills may have been present in their common ancestor before humans evolved their own complex forms of collaboration.

Analysis of Variance↗
PubMed1999

Complexity, pattern, and evolutionary trade-offs in animal aggregation.

One of the most striking patterns in biology is the formation of animal aggregations. Classically, aggregation has been viewed as an evolutionarily advantageous state, in which members derive the benefits of protection, mate choice, and centralized information, balanced by the costs of limiting resources. Consisting of individual members, aggregations nevertheless function as an integrated whole, displaying a complex set of behaviors not possible at the level of the individual organism. Complexity theory indicates that large populations of units can self-organize into aggregations that generate pattern, store information, and engage in collective decision-making. This begs the question, are all emergent properties of animal aggregations functional or are some simply pattern? Solutions to this dilemma will necessitate a closer marriage of theoretical and modeling studies linked to empirical work addressing the choices, and trajectories, of individuals constrained by membership in the group.

Animals↗
PubMed2000

Fairness versus reason in the ultimatum game.

In the Ultimatum Game, two players are offered a chance to win a certain sum of money. All they must do is divide it. The proposer suggests how to split the sum. The responder can accept or reject the deal. If the deal is rejected, neither player gets anything. The rational solution, suggested by game theory, is for the proposer to offer the smallest possible share and for the responder to accept it. If humans play the game, however, the most frequent outcome is a fair share. In this paper, we develop an evolutionary approach to the Ultimatum Game. We show that fairness will evolve if the proposer can obtain some information on what deals the responder has accepted in the past. Hence, the evolution of fairness, similarly to the evolution of cooperation, is linked to reputation.

Choice Behavior↗
PubMed1999

Dependency, self-criticism, interpersonal behaviour and affect: evolutionary perspectives.

Evolutionary accounts of vulnerability to depression have focussed either on the attachment system (Bowlby, 1980) or the social rank system (Gilbert, 1992; Price, 1972). According to a two-factor evolutionary model, depression-prone dependent and self-critical individuals suffer from insecurities regarding both attachment and social rank, but they differ in their strategies for dealing with those insecurities. Event-contingent recording was used to assess agentic (dominant-submissive) and communal (agreeable-quarrelsome) interpersonal behaviour as well as affect in 119 employed adults over 20 days. Participants also completed questionnaire measures of agency and communion. Self-criticism predicted low levels of agency and low levels of communion. In the sample as a whole, agentic and communal behaviours were associated with pleasant affect, but highly self-critical participants experienced relatively less pleasant affect when they acted communally or agentically. Individuals with high levels of immature dependency (neediness) were low in agency, whereas those with high levels of mature dependency (connectedness) were high in communion. Implications for evolutionary theories of vulnerability to depression were discussed, and interpersonal processes that may contribute to vulnerability were identified.

Adult↗
PubMed2005

Effects of perceived risk and strength of affiliation on decisions to help others: toward a convergence of evolutionary and social psychology.

In this study, the influence of perceived affiliation with a target and perceived risk on decisions to act altruistically were investigated. These are variables which have been suggested by the social and evolutionary psychology literatures, respectively. 12 participants responded to automobile accident scenarios that combined risk and affiliation with a target in descriptions of opportunities to render aid. Participants reported a lower likelihood to help when perceived risk was high, but only if their perceived affiliation with the targets was low or moderate; tendency to help highly affiliated targets was uniformly high throughout all risk conditions. Participants' ratings of certainty in their decisions to render aid were directly related to both perceived risk and perceived affiliation with a target. Decisions were arrived at more slowly when perceived risk and perceived affiliation were both moderate. Therefore, both risk and affiliation were considered by participants when deciding whether to act altruistically. This illustrates a convergence of predictions from social and evolutionary psychology.

Accidents, Traffic↗
PubMed1992

[Biomaterials and infection in dental and maxillofacial surgery].

Based on metals, polymers, ceramics, carbons or natural products, biomaterials represent an essential contribution to the repair or reconstruction of the hard or soft tissues of the dental and maxillofacial area. In order to avoid unsuccessful results these materials should realize a satisfactory tissue integration without bacterial colonization able to compromise the tissue-biomaterial finalized cooperation. The evolution of the science and technology of biomaterials should allow to get tissue toxicity-free materials which also inhibit microorganisms adherence, the infectability becoming a criteria as important as the biocompatibility itself.

Biocompatible Materials↗
PubMedDate not supplied

The selfish karyotype. An analysis of the biological basis of morals.

An analysis is made of the kin-selection/group-selection debate on the issue of the biological basis of morals. The kin-selection view sees altruism, and morals in the case of humans, as resting solely on genetic factors; in fact, on this view, evolution itself is to take place only through genetic change -- a position which cannot be reconciled with our knowledge that species evolution involves karyotypic change. Morality is thought to stem from a particular gene which at one time was completely absent from the human population but which later entered and spread through it. On the generally accepted conception of kin selection, this 'altruistic' gene is to be responsible not only for apparently altruistic behaviour towards near relatives, but also for parental care. Thus this view, among other things, has the absurd consequence that there was a period directly after humans first came into existence during which we did not care for our young. In contrast, the group-selection view, as developed here, sees morality as stemming from the species' karyotype, and to be passed on karyotypically from species to species through evolution. As suggested by Darwin, morality is thus derived from our social instincts, and is fundamentally directed to members of one's tribe or community, not to members of one's family. In keeping with this perspective, it is suggested here that the biological basis of morals does not concern the continuation of each individual's gene line, but the continuing existence of the individual's community, and thus, indirectly, the survival of the human species, through supporting the continuing instantiation of its karyotype.

Altruism↗
PubMed1998

The significance of relatedness and gene flow on population genetic structure in the®subsocial spider Eresus cinnaberinus (Araneae: Eresidae)

Interdemic selection, inbreeding and highly structured populations have been invoked to explain the evolution of cooperative social behaviour in the otherwise solitary and cannibalistic spiders. The family Eresidae consists of species ranging from solitary and intermediate subsocial to species exhibiting fully cooperative social behaviour. In this study we, in a hierarchical analysis, investigated relatedness of putative family clusters, inbreeding and population genetic structure of the subsocial spider Eresus cinnaberinus. Five hierarchical levels of investigation ranging from large scale genetic structure (distances of 250 and 50 km level 1 and 2) over microgeographic structure (20 km2 and 4 km2, level 3 and 4) to a single hill transect of 200 m (level 5) were performed. The purpose of level 5 was two-fold: (1) to investigate the relatedness of putative family groups, and (2) to evaluate the influence of both family living and sampling design on higher level estimates. Relatedness estimates of putative family groups showed an average relatedness of R=0.26. There was no indication of inbreeding. In contrast to social spiders, genetic variation was abundant, Heapproximately0.10. The population genetic structure was intermediate between social and asocial spiders. Genetic variance increased continually across hierarchical levels. Family structured neighbourhoods biased differentiation estimates among level 5 samples (FST=0.04) and level 3 and 4 samples (0.07 0, was caused by disjunct sampling from separate neighbourhoods. Larger scale samples were highly differentiated 0.12<FST<0.26, depending on level and sampling design. Due to a distance effect family living did not influence estimates of the higher level 1. Although the dispersing sex among social spiders and the subsocial E. cinnebarinus differ, females versus males, female behaviour of both sociality classes lead to high genetic variance.Copyright 1998 The Linnean Society of London

Journal Article↗
PubMed2004

Evolution of coordinated alternating reciprocity in repeated dyadic games.

A genetic algorithm incorporating mutation and crossing-over was used to investigate the evolution of social behaviour in repeated Prisoner's Dilemma, Chicken (Hawk-Dove), Battle of the Sexes, and Leader games. The results show that the strategic structure of an interaction has a crucial determining effect on the type of social behaviour that evolves. In particular, simulations using repeated Prisoner's Dilemma and Chicken (Hawk-Dove) games lead to the emergence of genes coding for symmetric reciprocity and the evolution of mutual cooperation, whereas simulations using repeated Battle of the Sexes and Leader games lead to near-fixation of genes coding for asymmetric strategic choices and the evolution of coordinated alternating reciprocity. A mechanism is suggested whereby, in games with asymmetric equilibrium points, coordinated alternating reciprocity might evolve without insight or communication between players.

Algorithms↗
PubMed2002

Altruistic punishment in humans.

Human cooperation is an evolutionary puzzle. Unlike other creatures, people frequently cooperate with genetically unrelated strangers, often in large groups, with people they will never meet again, and when reputation gains are small or absent. These patterns of cooperation cannot be explained by the nepotistic motives associated with the evolutionary theory of kin selection and the selfish motives associated with signalling theory or the theory of reciprocal altruism. Here we show experimentally that the altruistic punishment of defectors is a key motive for the explanation of cooperation. Altruistic punishment means that individuals punish, although the punishment is costly for them and yields no material gain. We show that cooperation flourishes if altruistic punishment is possible, and breaks down if it is ruled out. The evidence indicates that negative emotions towards defectors are the proximate mechanism behind altruistic punishment. These results suggest that future study of the evolution of human cooperation should include a strong focus on explaining altruistic punishment.

Altruism↗
PubMed1998

The spacing between binding sites controls the mode of cooperative DNA-protein interactions: implications for evolution of regulatory circuitry.

The CI repressors of lambdoid phages bind cooperatively to adjacent binding sites. Although these binding sites are found at complex operators containing three binding sites, cooperative binding occurs only between dimers bound at two of the sites, a mode of binding termed pairwise cooperativity. At the level of regulation, pairwise cooperativity allows the proper operation of the genetic switch. At the mechanistic level, it has been proposed to result from steric distortion of the complex, such that a protein dimer bound to a central site cannot contact both flanking dimers because it "leans" towards one of the two sites. We have tested this model using the CI repressor of phage HK022. Previous work suggested that reducing the spacing between adjacent operators might allow cooperative interaction among three dimers, a mode of cooperativity we term extended. Using a set of synthetic templates, we have shown that reducing the spacing allows extended cooperativity among three binding sites. Accordingly, the mode of cooperativity changes qualitatively in response to changes in the inter-site spacing. That is, the change in spacing has major functional consequences for the properties of the complex. We suggest that such changes can play important roles in the evolution of gene regulatory circuitry and of other processes involving nucleoprotein complexes.

Bacteriophage lambda↗