3,424 research outputs found
The Evolution of Altruism in Spatially Structured Populations
The evolution of altruism in humans is still an unresolved puzzle. Helping other individuals is often kinship-based or reciprocal. Several examples show, however, that altruism goes beyond kinship and reciprocity and people are willing to support unrelated others even when this is at a cost and they receive nothing in exchange. Here we examine the evolution of this "pure" altruism with a focus on altruistic teaching. Teaching is modeled as a knowledge transfer which enhances the survival chances of the recipient, but reduces the reproductive efficiency of the provider. In an agent-based simulation we compare evolutionary success of genotypes that have willingness to teach with those who do not in two different scenarios: random matching of individuals and spatially structured populations. We show that if teaching ability is combined with an ability to learn and individuals encounter each other on a spatial proximity basis, altruistic teaching will attain evolutionary success in the population. Settlement of the population and accumulation of knowledge are emerging side-products of the evolution of altruism. In addition, in large populations our simple model also produces a counterintuitive result that increasing the value of knowledge keeps fewer altruists alive.Altruism, Teaching, Knowledge Transfer, Spatially Structured Social Dilemmas
Evolution of Helping and Harming in Viscous Populations When Group Size Varies
Funding: Balliol College and the Royal Society.Recent years have seen huge interest in understanding how demographic factors mediate the evolution of social behavior in viscous populations. Here we study the impact of variation in group size on the evolution of helping and harming behavior. Although variation in group size influences the degree of relatedness and the degree of competition between groupmates, we find that these effects often exactly cancel, so as to give no net impact of variation in group size on the evolution of helping and harming. Specifically, (1) obligate helping and harming are never mediated by variation in group size, (2) facultative helping and harming are not mediated by variation in group size when this variation is spatial only, (3) facultative helping and harming are mediated by variation in group size only when this variation is temporal or both spatial and temporal, and (4) when there is an effect of variation in group size, facultative helping is favored in big groups and facultative harming is favored in little groups. Moreover, we find that spatial and temporal heterogeneity in individual fecundity may interact with patch-size heterogeneity to change these predictions, promoting the evolution of harming in big patches and of helping in little patches.Publisher PDFPeer reviewe
Network Homophily and the Evolution of the Pay-It-Forward Reciprocity
The pay-it-forward reciprocity is a type of cooperative behavior that people who have benefited from others return favors to third parties other than the benefactors, thus pushing forward a cascade of kindness. The phenomenon of the pay-it-forward reciprocity is ubiquitous, yet how it evolves to be part of human sociality has not been fully understood. We develop an evolutionary dynamics model to investigate how network homophily influences the evolution of the pay-it-forward reciprocity. Manipulating the extent to which actors carrying the same behavioral trait are linked in networks, the computer simulation model shows that strong network homophily helps consolidate the adaptive advantage of cooperation, yet introducing some heterophily to the formation of network helps advance cooperation's scale further. Our model enriches the literature of inclusive fitness theory by demonstrating the conditions under which cooperation or reciprocity can be selected for in evolution when social interaction is not confined exclusively to relatives
The bargaining model of depression
Minor depression—low mood often accompanied by a loss of motivation—is almost certainly an adaptation to circumstances that, in ancestral environments, imposed a fitness cost. It is, in other words, the psychic equivalent of physical pain. Major depression is characterized by additional symptoms—such as loss of interest in virtually all activities and suicidality—that have no obvious utility. The frequent association of these severe and disabling symptoms with apparently functional symptoms like sadness and low mood challenges a functional account of depression as a whole. Given that the principle cause of major unipolar depression is a significant negative life event, and that its characteristic symptom is a loss of interest in virtually all activities, it is possible that this syndrome functions somewhat like a labor strike. When powerful others are benefiting from an individual’s efforts, but the individual herself is not benefiting, she can, by reducing her productivity, put her value to them at risk in order to compel their consent and assistance in renegotiating the social contract so that it will yield net fitness benefits for her. In partial support of this hypothesis, depression is associated with the receipt of considerable social benefits despite the negative reaction it causes in others
Pathways to social evolution: reciprocity, relatedness, and synergy
Many organisms live in populations structured by space and by class, exhibit
plastic responses to their social partners, and are subject to non-additive
ecological and fitness effects. Social evolution theory has long recognized
that all of these factors can lead to different selection pressures but has
only recently attempted to synthesize how these factors interact. Using models
for both discrete and continuous phenotypes, we show that analyzing these
factors in a consistent framework reveals that they interact with one another
in ways previously overlooked. Specifically, behavioral responses
(reciprocity), genetic relatedness, and synergy interact in non-trivial ways
that cannot be easily captured by simple summary indices of assortment. We
demonstrate the importance of these interactions by showing how they have been
neglected in previous synthetic models of social behavior both within and
between species. These interactions also affect the level of behavioral
responses that can evolve in the long run; proximate biological mechanisms are
evolutionarily stable when they generate enough responsiveness relative to the
level of responsiveness that exactly balances the ecological costs and
benefits. Given the richness of social behavior across taxa, these interactions
should be a boon for empirical research as they are likely crucial for
describing the complex relationship linking ecology, demography, and social
behavior.Comment: 4 figure
Population Dynamics Constrain the Cooperative Evolution of Cross-Feeding
Cross-feeding is the exchange of nutrients among species of microbes. It has two
potential evolutionary origins, one as an exchange of metabolic wastes or
byproducts among species, the other as a form of cooperation known as reciprocal
altruism. This paper explores the conditions favoring the origin of cooperative
cross-feeding between two species. There is an extensive literature on the
evolution of cooperation, and some of the requirements for the evolution of
cooperative cross-feeding follow from this prior work–specifically the
requirement that interactions be limited to small groups of individuals, such as
colonies in a spatially structured environment. Evolution of cooperative
cross-feeding by a species also requires that cross-feeding from the partner
species already exists, so that the cooperating mutant will automatically be
reciprocated for its actions. Beyond these considerations, some unintuitive
dynamical constraints apply. In particular, the benefit of cooperative
cross-feeding applies only in the range of intermediate cell densities. At low
density, resource concentrations are too low to offset the cost of cooperation.
At high density, resources shared by both species become limiting, and the two
species become competitors. These considerations suggest that the evolution of
cooperative cross-feeding in nature may be more challenging than for other types
of cooperation. However, the principles identified here may enable the
experimental evolution of cross-feeding, as born out by a recent study
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