[Origin and evolution of legislation on social insurance in Italy].
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Biological Evolution↗
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Rescue of social motility lost during evolution of Myxococcus xanthus in an asocial environment.
Replicate populations of the social bacterium Myxococcus xanthus underwent extensive evolutionary adaptation to an asocial selective environment (liquid batch culture). All 12 populations showed partial or complete loss of their social (S) motility function after 1,000 generations of evolution. Mutations in the pil gene cluster (responsible for type IV pilus biogenesis and function) were found to be at least partially responsible for the loss of S motility in the majority of evolved lines. Restoration (partial or complete) of S motility in the evolved lines by genetic complementation with wild-type pil genes positively affected their fruiting body development and sporulation while negatively affecting their competitive fitness in the asocial regime. This genetic tradeoff indicates that mutations in the pil region were adaptive in the asocial selective environment. This finding was confirmed by experiments showing that defined deletions of pil gene regions conferred a competitive advantage under asocial conditions. Moreover, an amino acid substitution in an evolved genotype was located in a region predicted by genetic complementation analysis to bear an adaptive mutation.
Biological Evolution↗
Social roles and the evolution of networks in extreme and isolated environments.
This article reports on the evolution of network structure as it relates to formal and informal social roles in well-bounded, isolated groups. Research was conducted at the Amundsen-Scott South Pole Station. Data were collected on crewmembers' networks of social interaction over each of three winter-over periods, when the station is completely isolated. In addition, data were collected on the informal roles played by crewmembers (e.g., instrumental leadership, expressive leadership). The study found that globally coherent networks in winter-over groups were associated with group consensus on the presence of critically important informal social roles (e.g., expressive leadership) where global coherence is the extent to which a network forms a single group composed of a unitary core and periphery as opposed to being factionalized into two or more subgroups. Conversely, the evolution of multiple subgroups was associated with the absence of consensus on critical informal social roles, above all the critically important role of instrumental leader.
Adaptation, Psychological↗
[Evolution of anti-social behavior in hospitalized mental patients].
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Biological Evolution↗
[The evolution and characteristics of social hygiene in modern Japan].
The purpose of this paper is the clarification of the theory of social hygiene and its conception in modern society. The theory of social hygiene in modern society was mainly formed by the influence of social democracy and the social reform movement. Social hygiene in modern Japan was presented by Germany in the middle Meiji era and prevailed in the Taisho era. Yoshie Fukuhara, Gito Terouka and Teido Kunisaki developed the mainstream of the theory about social hygiene in modern Japan. The principle of social hygiene in Japan was that the target group of social hygienic activities (such as laborers, poor people, consumers of medical service and so on) should establish the idea of self-government and autonomy of their lives. Social supports to the target group were recognized as combining with the idea of self-government and autonomy of lives. Some of those activities influenced by the principle were performed. Particularly, the work of Tetsuo Hoshino was unique in showing the relation between health and human culture. The work has shown that human health is reflected in human cultural activities. Social hygiene was important to the foundation of introduction and evolution of the thoughts of public health, health culture and medical insurance in modern Japan.
Health↗
Kin selection, social structure, gene flow, and the evolution of chimpanzees.
Hypotheses about chimpanzee social behavior, phylogeography, and evolution were evaluated by noninvasive genotyping of free-ranging individuals from 20 African sites. Degrees of relatedness among individuals in one community were inferred from allele-sharing at eight nuclear simple sequence repeat (SSR) loci. Males are related on the order of half-siblings, and homozygosity is significantly increased at several SSR loci compared to Hardy-Weinberg expectations. These data support the kin-selection hypothesis for the evolution of cooperation among males. Sequence variation patterns at two mitochondrial loci indicate historically high long-distance gene flow and clarify the relationships among three allopatric subspecies. The unexpectedly large genetic distance between the western subspecies, Pan troglodytes verus, and the other two subspecies suggests a divergence time of about 1.58 million years. This result, if confirmed at nuclear loci and supported by eco-behavioral data, implies that P. t. verus should be elevated to full species rank.
Africa↗
Social roles, context and evolution in the origins of depression.
This paper reviews the author's research on the social origins of depression begun in the early 1970s. It emphasizes the importance of taking account of the context and meaning of proximal causal factors by the use of investigator-based ratings using intensive interviews and the need to extend research to cover a whole lifetime. The implications of the research program that has involved some twenty inquiries in a variety of cultural settings is discussed in terms of the importance of both a comparative and an evolutionary perspective concerning meaning that bring together the biology involved in an evolutionary perspective emphasizing a common human nature with one that takes account of cultural and individual differences. In short an approach that take seriously a biopsychosocial perspective.
Causality↗
Dynamics of social balance on networks.
We study the evolution of social networks that contain both friendly and unfriendly pairwise links between individual nodes. The network is endowed with dynamics in which the sense of a link in an imbalanced triad--a triangular loop with one or three unfriendly links--is reversed to make the triad balanced. With this dynamics, an infinite network undergoes a dynamic phase transition from a steady state to "paradise"--all links are friendly--as the propensity p for friendly links in an update event passes through 1/2 . A finite network always falls into a socially balanced absorbing state where no imbalanced triads remain. If the additional constraint that the number of imbalanced triads in the network not increase in an update is imposed, then the network quickly reaches a balanced final state.
Adaptation, Physiological↗
The evolution of nonhuman primate social behavior.
A review of the recent literature concerning evolutionary mechanisms and possible genetic contributions to social behavior reveals a concentration on function rather than mechanism. Although functional consequences may influence future genetic changes in a population, they do not necessarily reflect evolutionary history. More important, genes cannot code for functions. Only when the anatomical structures and behavioral patterns of individuals are described can we study genetic contributions to social organization. Discussions of function in the abstract, without specification of mechanism, do not fall within the realm of scientific testing.
Animals↗
[The human brain as a higher stage of the evolution of living matter: social matter].
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Animals↗
Higher disease prevalence can induce greater sociality: a game theoretic coevolutionary model.
There is growing evidence that communicable diseases constitute a strong selective force on the evolution of social systems. It has been suggested that infectious diseases may determine upper limits of host sociality by, for example, inducing territoriality or early juvenile dispersal. Here we use game theory to model the evolution of host sociality in the context of communicable diseases. Our model is then augmented with the evolution of virulence to determine coevolutionarily stable strategies of host sociality and pathogen virulence. In contrast to a controversial hypothesis by Ewald (1994), our analysis indicates that pathogens may become more virulent when contact rates are low, and their prevalence can ultimately induce greater sociality.
Biological Evolution↗
Reproductive ground plan may mediate colony-level selection effects on individual foraging behavior in honey bees.
The colony-level phenotype of an insect society emerges from interactions between large numbers of individuals that may differ considerably in their morphology, physiology, and behavior. The proximate and ultimate mechanisms that allow this complex integrated system to form are not fully known, and understanding the evolution of social life strategies is a major topic in systems biology. In solitary insects, behavior, sensory tuning, and reproductive physiology are linked. These associations are controlled in part by pleiotropic networks that organize the sequential expression of phases in the reproductive cycle. Here we explore whether similar associations give rise to different behavioral phenotypes in a eusocial worker caste. We document that the pleiotropic genetic network that controls foraging behavior in functionally sterile honey bee workers (Apis mellifera) has a reproductive component. Associations between behavior, physiology, and sensory tuning in workers with different foraging strategies indicate that the underlying genetic architectures were designed to control a reproductive cycle. Genetic circuits that make up the regulatory "ground plan" of a reproductive strategy may provide powerful building blocks for social life. We suggest that exploitation of this ground plan plays a fundamental role in the evolution of social insect societies.
Animals↗
Enhanced partner preference in a promiscuous species by manipulating the expression of a single gene.
The molecular mechanisms underlying the evolution of complex behaviour are poorly understood. The mammalian genus Microtus provides an excellent model for investigating the evolution of social behaviour. Prairie voles (Microtus ochrogaster) exhibit a monogamous social structure in nature, whereas closely related meadow voles (Microtus pennsylvanicus) are solitary and polygamous. In male prairie voles, both vasopressin and dopamine act in the ventral forebrain to regulate selective affiliation between adult mates, known as pair bond formation, as assessed by partner preference in the laboratory. The vasopressin V1a receptor (V1aR) is expressed at higher levels in the ventral forebrain of monogamous than in promiscuous vole species, whereas dopamine receptor distribution is relatively conserved between species. Here we substantially increase partner preference formation in the socially promiscuous meadow vole by using viral vector V1aR gene transfer into the ventral forebrain. We show that a change in the expression of a single gene in the larger context of pre-existing genetic and neural circuits can profoundly alter social behaviour, providing a potential molecular mechanism for the rapid evolution of complex social behaviour.
Animals↗
Evolution of an obligate social cheater to a superior cooperator.
Obligate relationships have evolved many times and can be parasitic or mutualistic. Obligate organisms rely on others to survive and thus coevolve with their host or partner. An important but little explored question is whether obligate status is an evolutionarily terminal condition or whether obligate lineages can evolve back to an autonomous lifestyle. The bacterium Myxococcus xanthus survives starvation by the social development of spore-bearing fruiting bodies. Some M. xanthus genotypes defective at fruiting body development in isolation can nonetheless exploit proficient genotypes in chimaeric groups. Here we report an evolutionary transition from obligate dependence on an altruistic host to an autonomous mode of social cooperation. This restoration of social independence was caused by a single mutation of large effect that confers fitness superiority over both ancestral genotypes, including immunity from exploitation by the ancestral cheater. Thus, a temporary state of obligate cheating served as an evolutionary stepping-stone to a novel state of autonomous social dominance.
Acetyltransferases↗
Density triggers soldier production in a social aphid.
For evolution and maintenance of the social system of insect colonies, investment in the sterile caste should be adequately controlled in response to environmental cues. Recent developments using artificial diet rearing techniques have revealed an underlying mechanism of caste control in a gall-forming aphid, Tuberaphis styraci, which has a soldier caste in the second instar. Statistical analyses of field-collected galls detected a significant positive correlation between aphid density and soldier proportion in the natural colonies of T. styraci. Artificial diet experiments showed that soldiers are produced under crowded conditions. Detailed experiments demonstrated that soldiers are produced in a density-dependent manner rather than in a colony size-dependent manner. From these results, it was concluded that aphid density is the crucial cue that triggers soldier production in T. styraci. This study provides, to our knowledge, the first experimental demonstration of an environmental factor involved in aphid soldier differentiation.
Animal Nutritional Physiological Phenomena↗
Ecdysteroid titer and reproduction in queens and workers of the honey bee and of a stingless bee: loss of ecdysteroid function at increasing levels of sociality?
Evidence from field wasps and bumblebees appoints the endocrine system as a mediator between dominance status and ovarian activity in primitively social Hymenoptera. In this comparative study on ecdysteroid titers in the highly social honey bee, Apis mellifera, and a stingless bee, Melipona quadrifasciata, we focussed on the relationship between the ecdysteroid titer, social conditions (presence or absence of the queen), and ovary activity. In contrast to bumblebees, ecdysteroid titers in honey bee and stingless bee workers were either not altered, or dropped to even lower levels after the queen was removed. We also did not detect differences between virgin queens and mated, egg laying queens. These results suggest that ecdysteroids may have lost most of their reproductive functions - yet gained functions in larval caste differentiation - as higher levels of social organization were attained in the evolution of social insects. The observation that ecdysteroid titers are transiently elevated in young workers adds a new, yet functionally still speculative facet to hormonal regulation in insect societies.
Animals↗
Tug-of-war over reproduction in a social bee.
One of the main transitions in evolution is the shift from solitary organisms to societies with reproductive division of labour. Understanding social evolution requires us to determine how ecological, social and genetic factors jointly influence group stability and partitioning of reproduction between group members. Here we test the role of the three key factors predicted to influence social evolution by experimentally manipulating them in a social allodapine bee. We show that increased relatedness between nestmates results in more even reproduction among group members and a greater productivity per individual. By contrast, the degree of reproductive skew is not influenced by the opportunity for solitary breeding or by the potential benefits of cooperation. Relatedness also has a positive effect on group stability and overall productivity. These findings are in line with predictions of the tug-of-war models, in which the degree of reproductive division of labour is determined primarily by selfish competition between group members. The alternative view, where the degree of reproductive skew is the outcome of a social contract between potential breeders, was not supported by the data.
Animals↗
Matriarchs as repositories of social knowledge in African elephants.
Despite widespread interest in the evolution of social intelligence, little is known about how wild animals acquire and store information about social companions or whether individuals possessing enhanced social knowledge derive biological fitness benefits. Using playback experiments on African elephants (Loxodonta africana), we demonstrated that the possession of enhanced discriminatory abilities by the oldest individual in a group can influence the social knowledge of the group as a whole. These superior abilities for social discrimination may result in higher per capita reproductive success for female groups led by older individuals. Our findings imply that the removal of older, more experienced individuals, which are often targets for hunters because of their large size, could have serious consequences for endangered populations of advanced social mammals such as elephants and whales.
Aging↗