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PubMed1989

Finite social space, evolutionary pathways, and reconstructing hominid behavior.

Changes in social behavior were a key aspect of human evolution, and yet it is notoriously difficult for paleobiologists to determine patterns of social evolution. By defining the limited number of distributional strategies available to members of each sex of any species and investigating the conditions under which they may occur and change, the social behavior of different hominid taxa may be reconstructed.

Animals↗
PubMed1978

Kin selection: A classical approach and a general solution.

The necessary conditions for the spread of genes that determine social behaviors and the rate of spread of these genes are derived for a simple model (single locus, two alleles, random mating, discrete generations) by using the classical population genetics approach pioneered by Haldane and the linear fitness function used previously by D. S. Wilson. These results are derived for social behaviors that are manifested by individuals within families, within pairs of families, or within groups of k families, for both diploid and haplodiploid organisms. I show that, when the groups of socially interacting individuals consist of the members of more than one family, severe restrictions are placed on the evolution of altruistic and social behaviors. Specifically, in these instances, the necessary conditions for the evolution of social behaviors are more stringent and the rate of evolution is greatly reduced.

Journal Article↗
PubMed1977

Towards a method for assessing social support systems.

Man is committed by his biological and cultural evolution to a social existence. While the social environment is the source of many stressors, it may also be protective. This latter function is called 'support'. Social bonds are to be found universally, but some cultural groups have the integrity of these bonds conspicuously endangered. The application of the affective component of the social network to psychiatry promises to be useful, but cannot progress further until an instrument is developed for assessing the support available to an individual. We have gone some way towards a method for assessing the components of primary group interaction. The task now is to determine if low social support, such as is seen in Western suburban wives, some migrant groups and some women in the Middle East and Asia, is causally related to some psychiatric disorders The principal appeal of this area is that we may be tapping something very fundamental about human social organisation, something which, unlike adversity, is subject to modification.

Community Psychiatry↗
PubMed1987

Pregnancy outcome and social conditions of women under 20: evolution in France from 1972 to 1981.

Two studies based on national samples of births in France in 1972 and 1981 have enabled a comparison of the changes in perinatal risk and social situation of women under 20 years of age with those of women 20 and over. Preterm delivery among women under 20 remained stable during the 10-year period, while it declined significantly among older women. Also, the social situation of teenagers deteriorated in terms of occupational activity, educational level, presence of the child's father in the home, and his occupation. The changes in these social characteristics do not adequately explain the increased relative risk of preterm delivery among women under 20.

Adolescent↗
PubMed1989

Host density and the evolution of parasite virulence.

Social and cultural habits of human populations affect the biological evolution of the agents of infectious diseases. Measles and similar diseases have evolved in the Old World and cannot have existed in their present form before the rise of the great river valley civilizations. It is suggested that increased virulence of measles in white and indigenous communities in America 1500-1800 may be due to a rare strain of the virus, which was selected during transfer from Europe. The release of viruses for biological pest control has provided new material for the study of the co-evolution of host-parasite systems, which has upset the dogma "evolution tends to avirulence". It is pointed out that this issue is closely related to the group selection debate among ethologists, i.e. to the problem: how can group selection overcome individual selection? A model is proposed in which differential growth of two strains of a parasite within the host and their transmission to new hosts is considered. It is supposed that transmission stages excreted by infectious hosts enter a common pool where they are mixed before infecting new hosts. Under these conditions, selection of the slower strain is possible only if the mean size of parasite inoculum is very small, i.e. if the density of transmission stages in the environment is low. The impact of this result on host pathology depends on the relation between virulence and transmission efficiency of the parasite.

Animals↗
PubMed1995

Maternity assignment and queen replacement in a social wasp.

Assigning offspring to parents is important for understanding the evolution of reproductive conflicts and cooperation, particularly in the model systems represented by social insects. Molecular genetic markers are often used to exclude, and occasionally used to assign, candidate parents. However, their use in social insects has been unsatisfactory so far because candidate mothers are often highly related and candidate fathers are unknown. Here, we show that microsatellite loci can be scored from each mother's stored sperm permitting effective maternity assignment. The theoretical power of this method is huge, and we demonstrate its practical utilization in this large-scale study of the wasp, Polistes annularis. All 219 genotyped daughters were either assigned to a unique mother or shown to be the progeny of an uncollected dead mother. The data reveal an unexpectedly high number of changes in reproductive dominance. Maternity assignments using this method should help solve many difficult questions in social evolution.

Alleles↗
PubMed2006

The evolution of worker caste diversity in social insects.

Morphological diversification of workers is predicted to improve the division of labor within social insect colonies, yet many species have monomorphic workers. Individual-level selection on the reproductive capacities of workers may counter colony-level selection for diversification, and life-history differences between species (timing of caste determination, colony size, genetic variation available) may mediate the strength of this selection. We tested this through phylogenetically independent contrast analyses on a new data set for 35 ant species. Evidence was found that early divergence of queen-worker developmental pathways may facilitate the evolution of worker diversity because queen-worker dimorphism was strongly positively associated with diversity. By contrast, risks for colonies that invest in specialized workers and colony size effects on costs of worker reproduction seem unlikely to strongly affect the evolution of worker diversity because there was no significant association between colony size and diversity when controlling statistically for queen-worker dimorphism. Finally, worker diversity was greater in species with multiple lineages per colony, and it was negatively associated with relatedness in monogynous species. This could be due to high intracolonial genetic variance favoring the expression and evolution of great worker diversity or to diversity evolving more easily when there is selection for repression of worker reproduction (worker policing).

Animals↗
PubMed1991

Evolution and facial action in reflex, social motive, and paralanguage.

Based upon current evolutionary theory and recent laboratory and field data, this paper introduces a behavioral-ecology view of human facial displays that contrasts with previous views of faces as innate, prototypic, "iconic" expressions of fundamental emotions. First, I detail the criteria for establishing genetic and epigenetic contributions to facial behavior. Under these criteria, cross-cultural communality in canonical facial displays implies neither their genetic control nor their fundamental relation to emotion. New findings reestablish phylogenetic continuity by showing that human facial displays and vigilance for them, like their nonhuman counterparts, coevolve in the service of social motives; faces issued in solitude typically reflect imaginary or implicit interaction. Two evolutionary trends are probably involved in shaping facial actions--emancipation of reflexes, and automatization of instrumental acts. Modern conceptions of genetic and cultural evolution, and knowledge about animal signaling, suggest new hypotheses regarding the origins and functions of facial displays. In so doing, they clarify how facial displays relate to reflexion, motive and intention, emotion and psychophysiology, and language and paralanguage.

Animals↗
PubMed2006

A simple rule for the evolution of cooperation on graphs and social networks.

A fundamental aspect of all biological systems is cooperation. Cooperative interactions are required for many levels of biological organization ranging from single cells to groups of animals. Human society is based to a large extent on mechanisms that promote cooperation. It is well known that in unstructured populations, natural selection favours defectors over cooperators. There is much current interest, however, in studying evolutionary games in structured populations and on graphs. These efforts recognize the fact that who-meets-whom is not random, but determined by spatial relationships or social networks. Here we describe a surprisingly simple rule that is a good approximation for all graphs that we have analysed, including cycles, spatial lattices, random regular graphs, random graphs and scale-free networks: natural selection favours cooperation, if the benefit of the altruistic act, b, divided by the cost, c, exceeds the average number of neighbours, k, which means b/c > k. In this case, cooperation can evolve as a consequence of 'social viscosity' even in the absence of reputation effects or strategic complexity.

Altruism↗