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Derex M.,Montpellier University | Godelle B.,Montpellier University | Raymond M.,Montpellier University | Raymond M.,CNRS Montpellier Institute of Evolutionary Sciences
Evolution | Year: 2013

Humans exhibit a rich and complex material culture with no equivalent in animals. Also, social learning, a crucial requirement for culture, is particularly developed in humans and provides a means to accumulate knowledge over time and to develop advanced technologies. However, the type of social learning required for the evolution of this complex material culture is still debated. Here, using a complex and opaque virtual task, the efficiency of individual learning and two types of social learning (product-copying and process-copying) were compared. We found that (1) individuals from process-copying groups outperformed individuals from product-copying groups or individual learners, whereas access to product information was not a sufficient condition for providing an advantage to social learners compared to individual learners; (2) social learning did not seem to affect the exploration of the fitness landscape; (3) social learning led to strong within-group convergence and also to between-group convergence, and (4) individuals used widely variable social learning strategies. The implications of these results for cumulative culture evolution are discussed. © 2012 The Author(s). Evolution © 2012 The Society for the Study of Evolution.

Derex M.,Montpellier University | Godelle B.,Montpellier University | Raymond M.,Montpellier University | Raymond M.,CNRS Montpellier Institute of Evolutionary Sciences
Evolution and Human Behavior | Year: 2014

The use of social information is a prerequisite to the evolution of culture. In humans, social learning allows individuals to aggregate adaptive information and increase the complexity of technology at a level unparalleled in the animal kingdom. However, the potential to use social information is related to the availability of this type of information. Although most cultural evolution experiments assume that social learners are free to use social information, there are many examples of information withholding, particularly in ethnographic studies. In this experiment, we used a computer-based cultural game in which players were faced with a complex task and had the possibility to trade a specific part of their knowledge within their groups. The dynamics of information transmission were studied when competition was within- or exclusively between-groups. Our results show that between-group competition improved the transmission of information, increasing the amount and the quality of information. Further, informational access costs did not prevent social learners from performing better than individual learners, even when between-group competition was absent. Interestingly, between-group competition did not entirely eliminate access costs and did not improve the performance of players as compared with within-group competition. These results suggest that the field of cultural evolution would benefit from a better understanding of the factors that underlie the production and the sharing of information. © 2014 Elsevier Inc.

Barthes J.,Montpellier University | Godelle B.,Montpellier University | Raymond M.,CNRS Montpellier Institute of Evolutionary Sciences
Evolution and Human Behavior | Year: 2013

Male homosexual preference (MHP) challenges evolutionary thinking because the preference for male-male relationships is heritable, implies a fertility cost (lower offspring number), and is relatively frequent in some societies (2%-6% in Western countries) for a costly trait. Proximate explanations include the hypothesis of a "sexually antagonistic factor" in which a trait that increases fertility in females also promotes the emergence of MHP. Because no animal species is known to display consistent MHP in the wild (only transient and contextual homosexual behavior has been described), additional human-specific features must contribute to the maintenance of MHP in human populations. We built a theoretical model that revealed that, in a stratified society, a relatively high frequency of MHP could be maintained as a result of the social ascension of females signaling high fertility (hypergyny). Additional computer simulations confirmed that this result applies to populations with various numbers of classes, conditions of demographic regulation, and mating systems. The prediction that MHP is more prevalent in stratified societies was significantly supported in a sample of 48 societies for which the presence or absence of MHP has been anthropologically documented. More generally, any traits associated with up-migration are likely to be selected for in a stratified society and will be maintained by frequency dependence even if they induce a pleiotropic cost, such as MHP. These results offer a new perspective for understanding seemingly paradoxical traits in human populations. © 2013 Elsevier Inc.

Barthes J.,Montpellier University | Crochet P.-A.,CNRS Center of Evolutionary and Functional Ecology | Raymond M.,Montpellier University | Raymond M.,CNRS Montpellier Institute of Evolutionary Sciences
PLoS ONE | Year: 2015

Male homosexual preference (MHP) has long been of interest to scholars studying the evolution of human sexuality. Indeed, MHP is partially heritable, induces a reproductive cost and is common. MHP has thus been considered a Darwinian paradox. Several questions arise when MHP is considered in an evolutionary context. At what point did MHP appear in the human evolutionary history? Is MHP present in all human groups? How has MHP evolved, given that MHP is a reproductively costly trait? These questions were addressed here, using data from the anthropological and archaeological literature. Our detailed analysis of the available data challenges the common view of MHP being a "virtually universal" trait present in humans since prehistory. The conditions under which it is possible to affirm that MHP was present in past societies are discussed. Furthermore, using anthropological reports, the presence or absence of MHP was documented for 107 societies, allowing us to conclude that evidence of the absence of MHP is available for some societies. A recent evolutionary hypothesis has argued that social stratification together with hypergyny (the hypergyny hypothesis) are necessary conditions for the evolution of MHP. Here, the link between the level of stratification and the probability of observing MHP was tested using an unprecedented large dataset. Furthermore, the test was performed for the first time by controlling for the phylogenetic non-independence between societies. A positive relationship was observed between the level of social stratification and the probability of observing MHP, supporting the hypergyny hypothesis. © 2015 Barthes et al.

Aouacheria A.,Ecole Normale Superieure de Lyon | Aouacheria A.,CNRS Montpellier Institute of Evolutionary Sciences
Biologie Aujourd'hui | Year: 2015

The concept of cell death has many links to the concept of death itself, defined as the opposite of life. Achievements obtained through research on apoptosis have apparently allowed us to transcend this Manichean view. Death is no longer outside, but rather inside living systems, as a constitutive force at work within the living matter. Whereas the death of cells can be positive and breed "creation" (e.g. during morphogenesis), its dysregulation can also cause or contribute to fatal diseases including cancer. It is tempting to apply this biological discourse to illuminate the relations between life and death, taken in general terms, but does this generalization actually hold? Is this discourse not essentially a metaphor? If cell death is considered as a vital aspect of various biological processes, then are we not faced with some vitalistic conception of death? Are there one or more meanings to the word "death"? Does the power to self-destruct act in opposition to other key features of living entities, or rather in juxtaposition to them? In this article, we first describe how the field of cell death has been developed on the basis of perceived and built dichotomies, mirroring the original opposition between life and death. We detail the limitations of the current paradigm of apoptosis regulation by BCL-2 family proteins, which nicely illustrate the problem of binary thinking in biology. Last, we try to show a way out of this dualistic matrix, by drawing on the notions of multiplicity, complexity, diversity, evolution and contingency. ©Socíeté de Biologie, 2016.

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