Extensive social choice and the measurement of group fitness in biological hierarchies

Extensive social choice theory is used to study the problem of measuring group fitness in a two-level biological hierarchy. Both fixed and variable group size are considered. Axioms are identified that imply that the group measure satisfies a form of consequentialism in which group fitness only depends on the viabilities and fecundities of the individuals at the lower level in the hierarchy. This kind of consequentialism can take account of the group fitness advantages of germ-soma specialization, which is not possible with an alternative social choice framework proposed by Okasha, but which is an essential feature of the index of group fitness for a multicellular organism introduced by Michod, Viossat, Solari, Hurand, and Nedelcu to analyze the unicellular-multicellular evolutionary transition. The new framework is also used to analyze the fitness decoupling between levels that takes place during an evolutionary transition.     

Carryover effects associated with winter location affect fitness, social status, and population dynamics in a long-distance migrant

We used observations of individually marked female black brant geese (Branta bernicla nigricans; brant) at three wintering lagoons on the Pacific coast of Baja California-Laguna San Ignacio (LSI), Laguna Ojo de Liebre (LOL), and Bahía San Quintín (BSQ)-and the Tutakoke River breeding colony in Alaska to assess hypotheses about carryover effects on breeding and distribution of individuals among wintering areas. We estimated transition probabilities from wintering locations to breeding and nonbreeding by using multistratum robust-design capture-mark-recapture models. We also examined the effect of breeding on migration to wintering areas to assess the hypothesis that individuals in family groups occupied higher-quality wintering locations. We used 4,538 unique female brant in our analysis of the relationship between winter location and breeding probability. All competitive models of breeding probability contained additive effects of wintering location and the 1997-1998 El Ni?o-Southern Oscillation (ENSO) event on probability of breeding. Probability of breeding in non-ENSO years was [Formula: see text], [Formula: see text], and [Formula: see text] for females wintering at BSQ, LOL, and LSI, respectively. After the 1997-1998 ENSO event, breeding probability was between 2% (BSQ) and 38% (LOL) lower than in other years. Individuals that bred had the highest probability of migrating the next fall to the wintering area producing the highest probability of breeding.     

Testosterone, cognition, and social status

What leads some people to perform better than others on certain cognitive tasks? One explanation involves individual differences in testosterone. Testosterone is associated with higher performance on spatial tests, and lower performance on verbal tests. However, a large literature suggests that testosterone only predicts behavior when status is in jeopardy. In the present study, we manipulated status before administering a spatial and verbal test. In a high-status position, high-testosterone individuals performed well on both tests, and blood pressure dropped. In a low-status position, high-testosterone individuals performed relatively poorly on both tests, and blood pressure did not change. These data suggest that differences in cognitive performance stem from an interaction between testosterone and the social situation.     

Serotonin, social status and aggression

Serotonin, social status and aggression appear to be linked in many animal species, including humans. The linkages are complex,and, for the most part, details relating the amine to the behavior remain obscure. During the past year, important advances have been made in a crustacean model system relating serotonin and aggression. The findings include the demonstration that serotonin injections will cause transient reversals in the unwillingness of subordinate animals to engage in agonistic encounters, and that at specific synaptic sites involved in activation of escape behavior, the direction of the modulation by serotonin depends on the social status of the animal.     

Allostatic load, social status and stress hormones: the costs of social status matter

Cooperation and social support are the major advantages of living in social groups. However, there are also disadvantages arising from social conflict and competition. Social conflicts may increase allostatic load, which is reflected in increased concentrations of glucocorticoids. We applied the emerging concept of allostasis to investigate the relation between social status and glucocorticoid concentrations. Animals in a society experience different levels of allostatic load and these differences may predict relative glucocorticoid concentrations of dominant and subordinate individuals. We reviewed the available data from free-ranging animals and generated, for each sex separately, phylogenetic independent contrasts of allostatic load and relative glucocorticoid concentrations. Our results suggest that the relative allostatic load of social status predicts whether dominants or subordinates express higher or lower concentrations of glucocorticoids. There was a significant correlation between allostatic load of dominance and relative glucocorticoid concentrations in both females and males. When allostatic load was higher in dominants than in subordinates, dominants expressed higher levels of glucocorticoids; when allostatic load was similar in dominants and subordinates, there were only minor differences in glucocorticoid concentrations; and when allostatic load was lower in dominants than in subordinates, subordinates expressed higher levels of glucocorticoids than dominants. To our knowledge, this is the first model that consistently explains rank differences in glucocorticoid concentrations of different species and sexes. The heuristic concept of allostasis thus provides a testable framework for future studies of how social status is reflected in glucocorticoid concentrations.     

Group size and direct fitness in social queues

We explore the effects of group size on the direct reproductive success of subordinate helpers in eusocial animals where only a single, dominant individual reproduces at one time. Helpers can reproduce directly if they inherit dominance, but when dominance is age based, an individual born into a larger group has a longer wait to inherit. We show that this disincentive to help can potentially be offset by increased productivity, increased life span, and insurance-based benefits for helpers if they survive to inherit dominance in larger groups. We analyze a field experiment in which group size was manipulated in the hover wasp Liostenogaster flavolineata. Productivity increased linearly with group size, larger groups were less likely to fail, and dominants in larger groups may have lived longer. Combined with the probability of inheriting dominance, these effects led overall to a negative correlation between group size and expected direct fitness, mainly because group size decreased during our study period, so that helpers could not expect to inherit as large a group as they started queuing in. Our analysis suggests that the relationship between group size and productivity plays a central role in determining the fitness consequences of helping.     

Individuals,groups, fitness and utility: multi-level selection meets social choice theory

In models of multi-level selection, the property of Darwinian fitness is attributed to entities at more than one level of the biological hierarchy, e.g. individuals and groups. However, the relation between individual and group fitness is a controversial matter. Theorists disagree about whether group fitness should always, or ever, be defined as total (or average) individual fitness. This paper tries to shed light on the issue by drawing on work in social choice theory, and pursuing an analogy between fitness and utility. Social choice theorists have long been interested in the relation between individual and social utility, and have identified conditions under which social utility equals total (or average) individual utility. These ideas are used to shed light on the biological problem.     

Social status,social context,and arterial blood pressure

As social change and economic development have proceeded, the prevalence of chronic diseases, especially cardiovascular diseases, has increased in the developing world. In part this is due to the adoption of diets and other health behaviors characteristic of industrialized nations; in part it is a function of changing social and economic circumstances. In this paper, we describe the development and testing of a model designed to account for social and economic effects on cardiovascular disease risk. The model incorporates the fact that global economic processes have made a lifestyle characterized by the consumption of Euroamerican material goods and information a basis for the assignment of social status in local communities. But economic change at the local level is rarely sufficient to provide a foundation for individuals' status aspirations. Hence, many individuals attempt to maintain a lifestyle inconsistent with their economic standing, a variable we term lifestyle incongruity. Here we describe how this factor is associated with higher blood pressure in a variety of settings and also how the effects of lifestyle incongruity can be modified in local contexts by social class and social role processes. This latter process, contextual modification, is illustrated by data from American Samoa. In this example, the association of lifestyle incongruity with blood pressure is examined in 30 male household heads and 26 spouses. After an examination of Samoan ethnography focused attention on the importance of age and gender differences as defining social contexts of intracultural variation, the model was modified to assess interactions between age and gender as they affect the association of lifestyle incongruity and blood pressure. Lifestyle incongruity is strongly associated with higher systolic and diastolic blood pressure for the younger household heads, minimally associated with blood pressure for older household heads, and only slightly associated with the blood pressure of their spouses. The regression coefficients for the lifestyle incongruity by age by sex interaction term was significant at P ≤ 0.01 for both systolic and diastolic blood pressure. The consistency of these results with expectations based on the ethnographic record is emphasized in the interpretation. We feel that the lifestyle incongruity model represents an empirically successful attempt to link global political-economic processes, local social structure, and biological outcomes. Am J Phys Anthropol 102:55–66, 1997. © 1997 Wiley-Liss, Inc.     

Child mortality, social status, and fertility in India

The incidence of child mortality in relation to the social status and fertility of Indian women was investigated on the assumptions that: 1) the higher the social status, the lower the child mortality rate; and 2) the lower the child mortality rate, the lower the family size. 311 married women in Chandigarh were grouped into 4 status categories: (1) higher educated working women (95); (2) higher educated nonworking women (75); (3) less educated nonworking women (75); and (4) less educated working women (66). The 311 women gave birth to a total of 1075 children (960 living and 115 who had died, mostly between the ages 0-5 years). Percentage of children living (89%) was different for each status category: 93% for category 1; 92% for category 2; 91% for category 3; and 81% for category 4. When analyzed by proportion of women who had lost children in each status category, the relationship between child mortality and social status confirmed the assumption that the higher the social status, the lower the mortality. In category 1, 87% had not experienced any child mortality in their family; in category 2, the figure was 77%; category 3, 72%; and category 4, 48%. The findings also confirmed the other assumption that the lower the mortality rate, the lower the fertility (Table 2).     

Perceived social isolation,evolutionary fitness and health outcomes: a lifespan approach

Sociality permeates each of the fundamental motives of human existence and plays a critical role in evolutionary fitness across the lifespan. Evidence for this thesis draws from research linking deficits in social relationship—as indexed by perceived social isolation (i.e. loneliness)—with adverse health and fitness consequences at each developmental stage of life. Outcomes include depression, poor sleep quality, impaired executive function, accelerated cognitive decline, unfavourable cardiovascular function, impaired immunity, altered hypothalamic pituitary–adrenocortical activity, a pro-inflammatory gene expression profile and earlier mortality. Gaps in this research are summarized with suggestions for future research. In addition, we argue that a better understanding of naturally occurring variation in loneliness, and its physiological and psychological underpinnings, in non-human species may be a valuable direction to better understand the persistence of a ‘lonely’ phenotype in social species, and its consequences for health and fitness.     

The effects of social status on biological aging as measured by white-blood-cell telomere length

Low socio-economic status (SES) is associated with a shortened life expectancy, but its effect on aging is unknown. The rate of white-blood-cell (WBC) telomere attrition may be a biological indicator of human aging. We tested the hypothesis that SES is associated with telomere attrition independent of known risk factors influencing the aging process. We studied 1552 female twins. A venous blood sample was taken from each twin and isolated WBCs used for extraction of DNA. Terminal restriction fragment length (TRFL) was measured. Questionnaire data were collected on occupation, education, income, smoking, exercise, height and weight. Standard multiple linear regression and multivariate analyses of variance tested for associations between SES and TRFL, adjusting for covariates. A discordant twin analysis was conducted on a subset to verify findings. WBC telomere length was highly variable but significantly shorter in lower SES groups. The mean difference in TRFL between nonmanual and manual SES groups was 163.2 base pairs (bp) of which 22.9 bp (approximately 14%) was accounted for by body mass index, smoking and exercise. Comparison of TRFL in the 17 most discordant SES twin pairs confirmed this difference. Low SES, in addition to the harmful effects of smoking, obesity and lack of exercise, appears to have an impact on telomere length.     

Wealth, status, and fitness: a historical study of Norwegians in variable environments

Wealth and status covary with lifetime reproductive success in preindustrial human populations. Local ecology is likely to modify this association, but details of this presumed relationship are not yet known. We sought to determine whether local ecology modifies the relationship between status and fitness (number of grandchildren). Our approach to the problem was to measure variation in fitness relative to status (landless or with land) and to local ecology (inland versus coastal communities). We also analyzed life history traits that might explain observed variations in fitness. Our results confirm previous findings that both status (landless=9.9 vs. with land=16.5) and ecology (inland=12.3 vs. coast=14.1) affect the number of grandchildren produced by a female in pre-industrial society. We also found that the differences in number of children between the status groups were less pronounced on the coast (landless=12.0 vs. with land=16.1) than inland (landless=7.8 vs. with land=16.8). Our findings are novel because they suggest that the fitness consequences of human status may depend on details of local ecology. We discuss four different mechanisms that could account for these fitness differences: (1) differential reproductive rate of mothers, (2) differential marriage rate of children (3) differential survival rate of children, and (4) different social practices (breastfeeding, inheritance of property and diet).     

Genomic admixture increases fitness during a biological invasion

Abstract During biological invasions, multiple introductions can provide opportunities for admixture among genetically distinct lineages. Admixture is predicted to contribute to invasion success by directly increasing fitness through hybrid vigour or by enhancing evolutionary potential within populations . Here, we demonstrate genome‐wide admixture during an invasion that substantially boosted fitness in the cosmopolitan weed, Silene vulgaris. We identified three divergent demes in the native European range that expanded from glacial refugia and experienced historical admixture in a well‐known suture zone. During recent invasion of North America, multiple introductions created additional opportunities for admixture. In common garden experiments, recombinant genotypes from North America experienced a two‐fold increase in fitness relative to nonrecombinants, whereas recombinant genotypes from Europe showed no lasting fitness benefits. This contrast implicates hybrid vigour behind the boost in fitness and supports the hypothesis that admixture can lead to fitness increases that may catapult invasion into a new range.     

Pride,personality, and the evolutionary foundations of human social status

Based on evolutionary logic, Henrich and Gil-White [Evolution and Human Behavior, 22(3), 165–196] distinguished between two routes to attaining social status in human societies: dominance, based on intimidation, and prestige, based on the possession of skills or expertise. Independently, emotion researchers Tracy and Robins [Journal of Personality and Social Psychology, 92(3), 506–525] demonstrated two distinct forms of pride: hubristic and authentic. Bridging these two lines of research, this paper examines whether hubristic and authentic pride, respectively, may be part of the affective-motivational suite of psychological adaptations underpinning the status-obtaining strategies of dominance and prestige. Support for this hypothesis emerged from two studies employing self-reports (Study 1), and self-and peer-reports of group members on collegiate athletic teams (Study 2). Results from both studies showed that hubristic pride is associated with dominance, whereas authentic pride is associated with prestige. Moreover, the two facets of pride are part of a larger suite of distinctive psychological traits uniquely associated with dominance or prestige. Specifically, dominance is positively associated with traits such as narcissism, aggression, and disagreeableness, whereas prestige is positively associated with traits such as genuine self-esteem, agreeableness, conscientiousness, achievement, advice-giving, and prosociality. Discussion focuses on the implications of these findings for our understanding of the evolutionary origins of pride and social status, and the interrelations among emotion, personality, and status attainment.     

Colour, fat and social status in male damselflies, Calopteryx maculata

In the black-winged damselfly, Calopteryx maculata, younger males challenge and displace older males from mating territories. Fatter males tend to win fights. These fights were initially interpreted as wars of attrition based on fat reserves, but the distributions of fat at the end of fights suggests at least some assessment of the opponent's condition. Alternatively, new models have been developed that show how the observed pattern could result without assessment. We show that there is a subtle but reliable cue to fat reserves: colour. Females are a relatively drab brown-black. Males are a strikingly iridescent blue-green colour, resulting from a multilayer constructive interference reflector system in the epicuticle. In fatter males the lamellae are more compressed and the peak reflectance is at shorter wavelengths (blue). Leaner, greener males have greater spacing between lamellae and reflect longer wavelengths. The peak reflectance is as predicted from transmission electron micrograph measurements of the lamellar spacing. The rate of change in spacing over time can be manipulated experimentally by manipulating the diet. Individuals on a higher food diet remained blue longer and at the end of the experiment were fatter and bluer. In our studies, colour is a better predictor of territorial status than fat. Copyright 2000 The Association for the Study of Animal Behaviour.     

Early and adult social environments have independent effects on individual fitness in a social vertebrate

Evidence that the social environment at critical stages of life-history shapes individual trajectories is accumulating. Previous studies have identified either current or delayed effects of social environments on fitness components, but no study has yet analysed fitness consequences of social environments at different life stages simultaneously. To fill the gap, we use an extensive dataset collected during a 24-year intensive monitoring of a population of Alpine marmots (Marmota marmota), a long-lived social rodent. We test whether the number of helpers in early life and over the dominance tenure length has an impact on litter size at weaning, juvenile survival, longevity and lifetime reproductive success (LRS) of dominant females. Dominant females, who were born into a group containing many helpers and experiencing a high number of accumulated helpers over dominance tenure length showed an increased LRS through an increased longevity. We provide evidence that in a wild vertebrate, both early and adult social environments influence individual fitness, acting additionally and independently. These findings demonstrate that helpers have both short- and long-term effects on dominant female Alpine marmots and that the social environment at the time of birth can play a key role in shaping individual fitness in social vertebrates.     

Modern economic growth and biological status

One of the most important recent findings of the anthropometric history research program is that human beings were becoming shorter at the onset of modern economic growth. There were hidden stresses on the biological system created by the new socio-economic environment that were not fully compensated by increases in income. This essay gives the outlines of an explanation for the "early-industrial-growth puzzle".