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The Social Epistasis Amplification Model: A Diachronic Test and Expansion of Theoretical Foundations
Abstract
We build on the finding of accumulating deleterious mutations with the SEAM (the social epistasis amplification model), which posits that the fitness costs of deleterious mutations are not limited to the organisms that carry them. This is possible in light of the existence of interorganismal genomic interactions, that is, social epistasis, whereby the genome of an organism (or the genomes of organisms) can influence another organism’s (or other organisms’) gene expression and therefore phenotypic traits.
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We tracked the relative integration and differentiation among life history traits over the period spanning AD 1800–1999 in the Britannic and Gallic biocultural groups. We found that Britannic populations tended toward greater strategic differentiation, while Gallic populations tended toward greater strategic integration. The dynamics of between-group competition between these two erstwhile rival biocultural groups were hypothesized as driving these processes. We constructed a latent factor that specifically sought to measure between-group competition and residualized it for the logarithmic effects of time. We found a significantly asymmetrical impact of between-group competition, where the between-group competition factor appeared to be driving the diachronic integration in Gallic populations but had no significantly corresponding influence on the parallel process of diachronic differentiation in Britannic populations. This suggests that the latter process was attributable to some alternative and unmeasured causes, such as the resource abundance consequent to territorial expansion rather than contraction.
We report successful diachronic replication of two major sets of prior findings in the
social biogeography of human life history (LH) strategy: (1) the constructive replication of
the diachronic changes in the latent hierarchical structure of intelligence in Britannic
populations, but as presently applied to the latent hierarchical structure of human LH
strategy, now cross-validated in both Britannic and Gallic populations; and (2) the
diachronic replication in both Britannic and Gallic populations of the structural relations
found synchronically among human LH strategy, between-group competition, and
economic productivity in cross-sectional data on contemporary samples of both national
and subnational polities. In addition, a supplementary methodological objective was: (3)
the convergent validation of diachronic lexicographic measures of LH strategy with
respect to more traditional non-lexicographic indicators of LH strategy, such as infant
mortality rates, total fertility rates, and life expectancies. We obtained complete
configural invariance across Britannic and Gallic biocultural groups, meaning that the
same model predictors were statistically significant, but incomplete metric invariance,
meaning that most but not all model parameter estimates were statistically equivalent in
magnitude and direction. All new results obtained from diachronic data in Britannic
populations were replicated almost perfectly in Gallic populations.
Although the relationship between social dominance status and reproductive success is universally positive in those species in which the relationship has been studied, in human societies today the relationship is more often negative. The present study uses detailed information from the General Social Survey in the United States to address this apparent paradox. Results show that education and intelligence had negative relationships with number of children across birth cohorts during most or all of the 20th century. Family income has only minor effects, especially when marital fertility rather than total cohort fertility is considered. The results do not support sociobiological predictions that modern humans turn material resources into reproductive success. Religion, ideology and income are identified as factors that influence the relationship between intelligence and fertility. Results are discussed in the broader context of emerging knowledge in demographics and molecular genetics, especially with respect to the direction of biological and cultural evolution in the modern United States and in modern societies more generally.
There is growing evidence that human ideology as well as social and political attitudes also have a genetic basis. In case of some genetic predisposition of political attitude, an association with fertility would be a hint of potential selection on political ideology. We therefore investigated on the basis of men and women that have completed, respectively, almost completed reproduction, of three different data sets (the World Value Survey 1981-2014 covering a wide range of countries and developmental levels, n = 152,380, the Survey of Health, Ageing and Retirement in Europe of 2005, n = 65,912, and the General Social Survey of the United States 1972-2014, n ⇠ 6200) whether political attitude is associated with number of children. Overall, in the world wide survey, both extreme political attitudes, albeit more pronounced for right/conservative than for left/liberal attitude, are associated with higher average offspring number compared to intermediate attitudes. If countries are analyzed separately, however, the picture is inconsistent, and in most countries, the association is non-significant. In the European and the US-survey, only the political right is associated with above average number of children. The time series of US data from 1972 to 2014 shows that at least in the US-sample, this pattern emerged during the 1990s: in the 1970s and 1980s, also in the US-sample both political extremes had a reproductive advantage, which vanished for left wing individuals during the 1990s. From an evolutionary perspective, we are not able to draw final conclusions as the association between political attitude and reproduction varies across countries and time. Nonetheless, the overall pattern suggests that in human evolutionary history, both left and right political attitudes may have conveyed fitness benefits so that both attitudes have been kept in the population.
Life history strategies reflect resource allocation decisions, which manifest as physiological, psychological, and behavioral traits. We investigated whether human ejaculate quality is associated with indicators of relatively fast (greater resource allocation to mating effort) or slow (greater resource allocation to parenting effort) life history strategies in a test of two competing hypotheses: (1) The phenotype-linked fertility hypothesis, which predicts that men pursuing a relatively fast life history strategy will produce higher-quality ejaculates, and (2) The cuckoldry-risk hypothesis, which predicts that men pursuing a relatively slow life history strategy will produce higher-quality ejaculates. Men (n = 41) completed a self-report measure assessing life history strategy and provided two masturbatory ejaculate samples. Results provide preliminary support for the cuckoldry-risk hypothesis: Men pursuing a relatively slow life history strategy produced higher-quality ejaculates. Ejaculate quality may therefore reflect resource allocation decisions for greater parenting effort, as opposed to greater mating effort. The findings contribute informative data on correlations between physiological and phenotypic indicators of life history strategies.
Biologists and social scientists have long tried to understand why some societies have more fluid and open interpersonal relationships and how those differences influence culture. This study measures relational mobility, a socioecological variable quantifying voluntary (high relational mobility) vs. fixed (low relational mobility) interpersonal relationships. We measure relational mobility in 39 societies and test whether it predicts social behavior. People in societies with higher relational mobility report more proactive interpersonal behaviors (e.g., self-disclosure and social support) and psychological tendencies that help them build and retain relationships (e.g., general trust, intimacy, self-esteem). Finally, we explore ecological factors that could explain relational mobility differences across societies. Relational mobility was lower in societies that practiced settled, interdependent subsistence styles, such as rice farming, and in societies that had stronger ecological and historical threats.
Conservatives report greater life satisfaction than liberals, but this relationship is relatively weak. To date, the evidence is limited to a narrow set of well-being measures that ask participants for a single assessment of their life in general. We address this shortcoming by examining the relationship between political orientation and well-being using measures of life satisfaction, affect, and meaning and purpose in life. Participants completed well-being measures after reflecting on their whole life (Studies 1a, 1b, and 2), at the end of their day (Study 3), and in the present moment (Study 4). Across five studies, conservatives reported greater meaning and purpose in life than liberals at each reporting period. This finding remained significant after adjusting for religiosity and was usually stronger than the relationships involving other well-being measures. Finally, meaning in life was more closely related to social conservatism than economic conservatism.
Theoretical models of critical mass have shown how minority groups can initiate social change dynamics in the emergence of new social conventions. Here, we study an artificial system of social conventions in which human subjects interact to establish a new coordination equilibrium. The findings provide direct empirical demonstration of the existence of a tipping point in the dynamics of changing social conventions. When minority groups reached the critical mass—that is, the critical group size for initiating social change—they were consistently able to overturn the established behavior. The size of the required critical mass is expected to vary based on theoretically identifiable features of a social setting. Our results show that the theoretically predicted dynamics of critical mass do in fact emerge as expected within an empirical system of social coordination.
Background and objectives:
The body mass index (BMI) is an established anthropometric index for the development of obesity-related conditions. However, little is known about the distribution of BMI within a population, especially about this distribution's temporal change. Here, we analysed changes in the distribution of height, weight and BMI over the past 140 years based on data of Swiss conscripts and tested for correlations between anthropometric data and standard blood parameters.
Methods:
Height and weight were measured in 59 504 young Swiss males aged 18-19 years during conscription in 1875-79, 1932-36, 1994 and 2010-12. For 65% of conscripts in 2010-12, results of standard blood analysis were available. We calculated descriptive statistics of the distribution of height, weight and BMI over the four time periods and tested for associations between BMI and metabolic parameters.
Results:
Average and median body height, body weight and BMI increased over time. Height did no longer increase between 1994 and 2010-12, while weight and BMI still increased over these two decades. Variability ranges of weight and BMI increased over time, while variation of body height remained constant. Elevated levels of metabolic and inflammatory blood parameters were found at both ends of BMI distribution.
Conclusions and implications:
Both overweight and underweight subgroups showed similar changes in inflammation parameters, pointing toward related metabolic deficiencies in both conditions. In addition to environmental influences, our results indicate a potential role of relaxed natural selection on genes affecting metabolism and body composition.
Fitness is always relative to the fitness of others in the group or breeding population. Even in very low-fertility societies, individual fitness as measured by the share of genes in subsequent generations may still be maximized. Further, sexual selection theory from evolutionary biology suggests that the relationship between status and fertility will differ for males and females. For this reason it is important to examine the relationship between status and fertility separately for males and females–something few demographic studies of fertility do. When male fertility is measured separately, high-status men (as measured by their wealth and personal income) have higher fertility than low-status men, even in very low-fertility societies, so individual males appear to be maximizing their fitness within the constraints posed by a modern society. Thus male fertility cannot be considered maladaptive. When female fertility is measured separately, in both very high- and very low-fertility societies, there is not much variance across women of different statuses in completed fertility. Only in societies currently changing rapidly (with falling fertility rates) is somewhat high variance across women of different statuses in completed fertility found. What is seen across all phases of the demographic transition appears to be a continuation of two somewhat different evolved human reproductive strategies–one male, one female–in changing social and material contexts. Whether contemporary female fertility is maladaptive remains an open question.
Humans tend to form social relationships with others who resemble them. Whether this sorting of like with like arises from historical patterns of migration, meso-level social structures in modern society, or individual-level selection of similar peers remains unsettled. Recent research has evaluated the possibility that unobserved genotypes may play an important role in the creation of homophilous relationships. We extend this work by using data from 5,500 adolescents from the National Longitudinal Study of Adolescent to Adult Health (Add Health) to examine genetic similarities among pairs of friends. Although there is some evidence that friends have correlated genotypes, both at the whole-genome level as well as at trait-associated loci (via polygenic scores), further analysis suggests that meso-level forces, such as school assignment, are a principal source of genetic similarity between friends. We also observe apparent social-genetic effects in which polygenic scores of an individual's friends and schoolmates predict the individual's own educational attainment. In contrast, an individual's height is unassociated with the height genetics of peers.
Like nonaffected adults, individuals with autism spectrum disorders (ASDs) show the entire range of sexual behaviors. However, due to the core symptoms of the disorder spectrum, including deficits in social skills, sensory hypo- and hypersensitivities, and repetitive behaviors, some ASD individuals might develop quantitatively above-average or nonnormative sexual behaviors and interests. After reviewing the relevant literature on sexuality in high-functioning ASD individuals, we present novel findings on the frequency of normal sexual behaviors and those about the assessment of hypersexual and paraphilic fantasies and behaviors in ASD individuals from our own study. Individuals with ASD seem to have more hypersexual and paraphilic fantasies and behaviors than general-population studies suggest. However, this inconsistency is mainly driven by the observations for male participants with ASD. This could be due to the fact that women with ASD are usually more socially adapted and show less ASD symptomatology. The peculiarities in sexual behaviors in ASD patients should be considered both for sexual education and in therapeutic approaches.
Industrialisation leads to relaxed selection and thus the accumulation of fitness-damaging genetic mutations. We argue that religion is a selected trait that would be highly sensitive to mutational load. We further argue that a specific form of religiousness was selected for in complex societies up until industrialisation based around the collective worship of moral gods. With the relaxation of selection, we predict the degeneration of this form of religion and diverse deviations from it. These deviations, however, would correlate with the same indicators because they would all be underpinned by mutational load. We test this hypothesis using two very different deviations: atheism and paranormal belief. We examine associations between these deviations and four indicators of mutational load: (1) poor general health, (2) autism, (3) fluctuating asymmetry, and (4) left-handedness. A systematic literature review combined with primary research on handedness demonstrates that atheism and/or paranormal belief is associated with all of these indicators of high mutational load.
What is the adapted structure of the behavioral immune system? By definition, the behavioral immune system motivates pathogen avoidance. One prominent suggestion is that the behavioral immune system also contains an additional component that generates motivation to avoid individuals from unfamiliar outgroups. The evolvability of this component has recently been questioned, however, and it has been noted that all supportive evidence stems from WEIRD samples. In this paper, we conducted between-subject experiments in large samples of adult residents of the USA (N = 1615) and India (N = 1969). In the experiment, we measured comfort with physical contact with a depicted individual. The individual was either from an ethnic ingroup or outgroup and either showed a pathogen cue or not. Results were inconsistent with the view that the behavioral immune system motivates the avoidance of individuals from unfamiliar outgroups. Instead, the results strongly supported that the system simply motivates the avoidance of any infected individual regardless of their group membership.
This study investigates the dimensions of cultural variation in the modern world as assessed by the World Values Survey. It confirms the previously reported existence of two major dimensions of cultural variation that can be described as “modern” and “postmodern,” respectively. Modern values are characterized by skepticism and critical thinking, with a rejection of religion and traditional authority along with an interest in politics. In multiple regression models, modern values are directly related to the IQ of the population. Postmodern values are characterized by trust, tolerance, and self-realization. In multiple regression models, they are inversely related to corruption. Subjective well-being is positively related to postmodern values and negatively to modern values. Modern values are interpreted as the emancipation of reason from the constraints of traditional custom and religion, and postmodern values as the emancipation of pleasure-seeking and social emotions from the constraints of dysfunctional social systems. The historical context and the roles of these value orientations in the evolution of contemporary societies are discussed.
Background:
Reported declines in sperm counts remain controversial today and recent trends are unknown. A definitive meta-analysis is critical given the predictive value of sperm count for fertility, morbidity and mortality.
Objective and rationale:
To provide a systematic review and meta-regression analysis of recent trends in sperm counts as measured by sperm concentration (SC) and total sperm count (TSC), and their modification by fertility and geographic group.
Search methods:
PubMed/MEDLINE and EMBASE were searched for English language studies of human SC published in 1981-2013. Following a predefined protocol 7518 abstracts were screened and 2510 full articles reporting primary data on SC were reviewed. A total of 244 estimates of SC and TSC from 185 studies of 42 935 men who provided semen samples in 1973-2011 were extracted for meta-regression analysis, as well as information on years of sample collection and covariates [fertility group ('Unselected by fertility' versus 'Fertile'), geographic group ('Western', including North America, Europe Australia and New Zealand versus 'Other', including South America, Asia and Africa), age, ejaculation abstinence time, semen collection method, method of measuring SC and semen volume, exclusion criteria and indicators of completeness of covariate data]. The slopes of SC and TSC were estimated as functions of sample collection year using both simple linear regression and weighted meta-regression models and the latter were adjusted for pre-determined covariates and modification by fertility and geographic group. Assumptions were examined using multiple sensitivity analyses and nonlinear models.
Outcomes:
SC declined significantly between 1973 and 2011 (slope in unadjusted simple regression models -0.70 million/ml/year; 95% CI: -0.72 to -0.69; P < 0.001; slope in adjusted meta-regression models = -0.64; -1.06 to -0.22; P = 0.003). The slopes in the meta-regression model were modified by fertility (P for interaction = 0.064) and geographic group (P for interaction = 0.027). There was a significant decline in SC between 1973 and 2011 among Unselected Western (-1.38; -2.02 to -0.74; P < 0.001) and among Fertile Western (-0.68; -1.31 to -0.05; P = 0.033), while no significant trends were seen among Unselected Other and Fertile Other. Among Unselected Western studies, the mean SC declined, on average, 1.4% per year with an overall decline of 52.4% between 1973 and 2011. Trends for TSC and SC were similar, with a steep decline among Unselected Western (-5.33 million/year, -7.56 to -3.11; P < 0.001), corresponding to an average decline in mean TSC of 1.6% per year and overall decline of 59.3%. Results changed minimally in multiple sensitivity analyses, and there was no statistical support for the use of a nonlinear model. In a model restricted to data post-1995, the slope both for SC and TSC among Unselected Western was similar to that for the entire period (-2.06 million/ml, -3.38 to -0.74; P = 0.004 and -8.12 million, -13.73 to -2.51, P = 0.006, respectively).
Wider implications:
This comprehensive meta-regression analysis reports a significant decline in sperm counts (as measured by SC and TSC) between 1973 and 2011, driven by a 50-60% decline among men unselected by fertility from North America, Europe, Australia and New Zealand. Because of the significant public health implications of these results, research on the causes of this continuing decline is urgently needed.
The relationship between intelligence and handedness remains a matter of debate. The present study is a systematic review of 36 studies (totaling 65,519 individuals), which have measured full IQ scores in different handedness groups. Eighteen of those studies were further included in three sets of meta-analyses (totaling 19,744 individuals), which investigated differences in standardized mean IQ scores in (i) left-handers, (ii) non-right-handers, and (iii) mixed-handers compared to right-handers. The bulk of the studies included in the systematic review reported no differences in IQ scores between left- and right-handers. In the meta-analyses, statistically significant differences in mean IQ scores were detected between right-handers and left-handers as well as right-handers and non-right-handers, but were marginal in magnitude (d=-.07 and d=-.06, respectively); the data sets were found to be homogeneous. Significance was lost when the largest study was excluded. No differences in mean IQ scores were found between right-handers and mixed-handers. No sex differences were found. Overall, the intelligence differences between handedness groups in the general population are negligible.
In most mammals, including humans, the postnatal acquisition of normal social and nonsocial behavior critically depends on interactions with peers. Here we explore the possibility that mixed-group housing of mice carrying a deletion of Nlgn3, a gene associated with autism spectrum disorders, and their wild-type littermates induces changes in each other’s behavior. We have found that, when raised together, male Nlgn3 knockout mice and their wild-type littermates displayed deficits in sociability. Moreover, social submission in adult male Nlgn3 knockout mice correlated with an increase in their anxiety. Re-expression of Nlgn3 in parvalbumin-expressing cells in transgenic animals rescued their social behavior and alleviated the phenotype of their wild-type littermates, further indicating that the social behavior of Nlgn3 knockout mice has a direct and measurable impact on wild-type animals’ behavior. Finally, we showed that, unlike male mice, female mice lacking Nlgn3 were insensitive to their peers’ behavior but modified the social behavior of their littermates. Altogether, our findings show that the environment is a critical factor in the development of behavioral phenotypes in transgenic and wild-type mice. In addition, these results reveal that the social environment has a sexually dimorphic effect on the behavior of mice lacking Nlgn3, being more influential in males than females.
In the literature, explanations of support for populist radical right (PRR) parties usually focus on voters’ socio-structural grievances, political discontent or policy positions. This article suggests an additional and possibly overarching explanation: societal pessimism. The central argument is that the nostalgic character of PRR ideology resonates with societal pessimism among its voters. Using European Social Survey data from 2012, the study compares levels of societal pessimism among PRR, radical left, mainstream left and mainstream right (MR) voters in eight European countries. The results show that societal pessimism is distributed in a tilted U-curve, with the highest levels indeed observed among PRR voters, followed by radical left voters. Societal pessimism increases the chance of a PRR vote (compared to a MR vote) controlling for a range of established factors. Further analyses show that societal pessimism is the only attitude on which MR and PRR voters take opposite, extreme positions. Finally, there is tentative evidence that societal pessimism is channelled through various more specific ideological positions taken by PRR voters, such as opposition to immigration.
Hayek’s social theory of evolution suggests that market liberal morality is adaptive for social groups. He justified the evolutionary superiority of market liberalism by asserting that groups operating under a market liberal morality would have a higher capacity to expand and reproduce than groups with alternative tribal moralities. Thus, market liberal groups would be favoured through cultural and genetic group selection. But in fact, market liberal morality reveals maladaptive tendencies and remains insufficiently powerful to create adaptive social groups. Hayek’s dismissal of moral tribalism in favour of market liberal morality is found to underestimate the importance of tribal goals in the evolutionary system.
The often-posed claim that Europe is a pessimistic continent is not unjustified. In 2012, 53 percent of European Union (EU) citizens were pessimistic about their country. Surprisingly, however, societal pessimism has received very little scientific attention. In this article, we examine to what extent political and economic factors drive societal pessimism. In terms of political factors, we expect that supranationalization, political instability, and corruption increase societal pessimism, as they diminish national political power and can inspire collective powerlessness. Economically, we expect that the retrenchment of welfare state provisions and economic decline drive societal pessimism, as these developments contribute to socioeconomic vulnerability. We assess the impact of these political and economic factors on the level of societal pessimism in the EU, both cross-nationally and over time, through multilevel analyses of Eurobarometer data (13 waves between 2006 and 2012 in 23 EU countries). Our findings show that the political factors (changes in government, corruption) primarily explain cross-national differences in societal pessimism, while the macro-economic context (economic growth, unemployment) primarily explains longitudinal trends within countries. These findings demonstrate that, to a large extent, societal pessimism cannot be viewed separately from its political and economic context.
Deleterious mutations are typically understood exclusively in terms of their harmful effects on carrier organisms. But there are convincing reasons to think that such adverse effects are not confined to the individual level. We argue that in social species, interorganismal gene-gene interactions, which in previous literatures have been termed social epistasis, allow genomes carrying deleterious mutations to reduce via group-level pleiotropy the fitness of others, including noncarriers. This fitness reduction occurs by way of degradation of group-level processes that optimize the reproductive ecology of a population for intergroup competition through, among other mechanisms, suppression of free-riding. Such damage to group regulatory processes suggests a hidden role for the accumulation of behavior-altering "spiteful" mutations in the dynamics of the demographic transition—these mutations may have contributed to the maladaptive outcomes of this process, such as widespread subreplacement fertility. A structured population model is presented describing aspects of this social epistasis amplification model. This phenomenon is also considered as a potential explanation for the results of Calhoun’s mouse utopia experiments, which provide an opportunity to directly test a major prediction stemming from the model.
Developmental theories of the biological basis of sexual orientation suggest that sexually differentiated psychological and behavioural traits should be linked with sexual orientation. Subgroups of gay men delineated by anal sex roles differ according to at least one such trait: gender expression. The present study assessed the hypothesis that handedness, a biologically determined sexually differentiated trait, corresponds to differences in subgroups of gay men based on anal sex role. Furthermore, it assessed whether handedness mediates the association between gender nonconformity and male sexual orientation. Straight and gay men (N = 333) completed the Edinburgh Inventory of Handedness and the Recalled Childhood Gender Nonconformity Scale. Gay men also completed measures of anal sex role preference. As in previous studies, gay men showed greater non-right-handedness and gender nonconformity than straight men. Also, among gay men, bottoms/versatiles (i.e., gay men who take a receptive anal sex role, or who take on both a receptive and insertive anal sex role) were more gender-nonconforming than tops (i.e., gay men who take an insertive anal sex role). In support of the hypothesis, bottoms/versatiles were more non-right-handed than tops and handedness mediated the male sexual orientation and anal sex role differences in Recalled Childhood Gender Nonconformity. Together, these findings suggest that developmental processes linked to handedness underpin variation among men in sexual orientation and gender nonconformity as well as variation among subgroups of gay men that are delineated by anal sex roles.
Worldwide rise of obesity may be partly related to the relaxation of natural selection in the last few generations. Accumulation of mutations affecting metabolism towards excessive fat deposition is suggested to be a result of less purging selection. Using the WHO and UN data for 159 countries there is a significant correlation (r = 0.60, p<0.01) between an index of the relaxed opportunity for selection (Biological State Index) and prevalence of obesity (percentage of individuals with BMI >30kg/m²). This correlation remains significant (r = 0.32., p<0.01) when caloric intake and insufficient physical activity prevalence are kept statistically constant (partial correlation analysis, N = 82). The correlation is still significant when gross domestic product per capita is also kept constant (r = 0.24, p <0.05, N = 81). In the last decades, prevalence of both obesity and underweight has increased in some countries despite no change in caloric intake nor in physical inactivity prevalence. Relaxed selection against genes affecting energy balance and metabolism may contribute to the increase of fatness independent from commonly considered positive energy balance. Diagnoses of individual predispositions to obesity at an early age and individual counselling on diet and behaviour may be appropriate strategies to limit further increases in body mass.
Since good-looking politicians win more votes, a beauty advantage for politicians on the left or on the right is bound to have political consequences. We show that politicians on the right look more beautiful in Europe, the United States and Australia. Our explanation is that beautiful people earn more, which makes them less inclined to support redistribution. Our model of within-party competition predicts that voters use beauty as a cue for conservatism when they do not know much about candidates and that politicians on the right benefit more from beauty in low-information elections. Evidence from real and experimental elections confirms both predictions.
Fluctuating asymmetry, the random deviation from perfect symmetry, is a widely used population-level index of developmental instability, developmental noise, and robustness. It reflects a population's state of adaptation and genomic coadaptation. Here, we review the literature on fluctuating asymmetry of human populations. The most widely used bilateral traits include skeletal, dental, and facial dimensions; dermatoglyphic patterns and ridge counts; and facial shape. Each trait has its advantages and disadvantages, but results are most robust when multiple traits are combined into a composite index of fluctuating asymmetry (CFA). Both environmental (diet, climate, toxins) and genetic (aneuploidy, heterozygosity, inbreeding) stressors have been linked to population-level variation in fluctuating asymmetry. In general, these stressors increase average fluctuating asymmetry. Nevertheless, there have been many conflicting results, in part because (1) fluctuating asymmetry is a weak signal in a sea of noise; and (2) studies of human fluctuating asymmetry have not always followed best practices. The most serious concerns are insensitive asymmetry indices (correlation coefficient and coefficient of indetermination), inappropriate size scaling, unrecognized mixture distributions, inappropriate corrections for directional asymmetry, failure to use composite indices, and inattention to measurement error. Consequently, it is often difficult (or impossible) to compare results across traits, and across studies.
Personality is influenced by genetic and environmental factors and associated with mental health. However, the underlying genetic determinants are largely unknown. We identified six genetic loci, including five novel loci, significantly associated with personality traits in a meta-analysis of genome-wide association studies (N = 123,132-260,861). Of these genome-wide significant loci, extraversion was associated with variants in WSCD2 and near PCDH15, and neuroticism with variants on chromosome 8p23.1 and in L3MBTL2. We performed a principal component analysis to extract major dimensions underlying genetic variations among five personality traits and six psychiatric disorders (N = 5,422-18,759). The first genetic dimension separated personality traits and psychiatric disorders, except that neuroticism and openness to experience were clustered with the disorders. High genetic correlations were found between extraversion and attention-deficit-hyperactivity disorder (ADHD) and between openness and schizophrenia and bipolar disorder. The second genetic dimension was closely aligned with extraversion-introversion and grouped neuroticism with internalizing psychopathology (e.g., depression or anxiety).
Political ideology represents an imperfect yet important indicator of a host of personality traits and cognitive preferences. These preferences, in turn, seemingly propel liberals and conservatives towards divergent life-course experiences. Criminal behavior represents one particular domain of conduct where differences rooted in political ideology may exist. Using a national dataset, we test whether and to what extent political ideology is predictive of self-reported criminal behavior. Our results show that self-identified political ideology is mono-tonically related to criminal conduct cross-sectionally and prospectively and that liberals self-report more criminal conduct than do conservatives. We discuss potential causal mechanisms relating political ideology to individual conduct.
This sequential canonical cascade model of social biogeography is an extension of an integrated model of human cognitive ecology (Cabeza de Baca & Figueredo, 2014) that predicted state-level life history and cognitive abilities in Mexico. We integrate such population-level factors by utilizing a sample of sixty-six recognized national polities for which sufficiently complete information was available on all the variables modeled. These national polities were limited to those found in Europe, Asia, and Africa. The Americas and Australia were excluded to avoid sampling parts of the world that had recently undergone massive colonizations by human and nonhuman animals and plants from other zoogeographic zones, which might have disrupted the evolutionarily expected relations between physical, community, and social human ecologies. Data were obtained from national census databases and international organizations, and only national polities with complete data were analyzed, meaning that no missing data were imputed based on values from nearby or otherwise similar polities. This integrated model of social biogeography proposes that abiotic climatic factors in the physical ecology as well as biotic factors in the community ecology produce variation in subsistence and natural resources that then impact biometric markers of life history, triggering changes in social equality, within-group and between-group peace, sexual equality, macroeconomic diversification, and human capital. These effects, in turn, ultimately produce changes in brain volume and aggregate cognitive abilities. The final equation in our cascade model explains 88% of the variance in aggregate cognitive abilities by supplying more detailed information on socioecological conditions than previous work.
Social behavior in animals is an adaptive process influenced by environmental factors and direct and indirect genetic effects. Indirect genetic effects (IGEs) include mechanisms by which individuals of particular genotypes can influence the behavioral phenotypes and genotypes (via modulated patterns of gene expression) of other individuals with different genotypes. In groups of adult mice, IGEs can be unidirectional, from one genotype to the other, or bidirectional, resulting in a homogenization of the behavioral phenotypes within the group. Critically, it has been theorized that IGEs constitute a large fitness target on which deleterious mutations can have pleiotropic effects, meaning that individuals carrying certain behavior-altering mutations can impose the fitness costs of those mutations on others comprising the broader social genome. Experimental data involving a mouse model support the existence of these IGE-amplified fitness losses; however, the underlying biological mechanisms that facilitate these remain unknown. In a mouse model of IGEs, we demonstrate that the Major Urinary Protein 20 pheromone, also called Darcin, produced by mice lacking the adhesion protein Neuroligin-3 acts as a vector to deleteriously modify the social behavior of wild-type mice. Additionally, we showed that lack of social interest on the part of Neuroligin-3 knockout mice is independent of their environment. These findings reveal a new role for mammalian pheromones in mediating the externalization of social deficits from one individual to others comprising the population through IGEs.
Author Summary
Indirect genetic effects (IGEs) are mechanisms by which individuals of particular genotypes can influence the behavioral phenotype of individuals of different genotypes, sometimes disruptively, in instances where one member of the population carriers a deleterious behavior altering variant. Although disruptive IGEs have been demonstrated in mice, its underlying molecular and genetic mechanisms remain unknown. Using an IGEs mouse model, we demonstrated that the pheromone protein Major Urinary Protein 20, also named Darcin, is as a vector and target of social epistasis a specific type of IGEs. This finding reveals a new function for mammalian pheromones in mediating social epistasis to degrade group social behavior.
Interactions between organisms are ubiquitous and have important consequences for phenotypes and fitness. Individuals can even influence those they never meet, if they have extended phenotypes that alter the environments others experience. North American red squirrels (Tamiasciurus hudsonicus) guard food hoards, an extended phenotype that typically outlives the individual and is usually subsequently acquired by non‐relatives. Hoarding by previous owners can, therefore, influence subsequent owners. We found that red squirrels breed earlier and had higher lifetime fitness if the previous hoard owner was a male. This was driven by hoarding behaviour, as males and mid‐aged squirrels had the largest hoards, and these effects persisted across owners, such that if the previous owner was male or died in mid‐age, subsequent occupants had larger hoards. Individuals can, therefore, influence each other's resource‐dependent traits and fitness without ever meeting, such that the past can influence contemporary population dynamics through extended phenotypes.
Animal models of conflict behavior predict that an organism's behavior in a conflict situation is influenced by physical characteristics related to abilities to impose costs on adversaries. Stronger and larger organisms should be more motivated to seek larger shares of resources and higher places in hierarchies. Previous studies of human males have suggested that measures of upper‐body strength are associated with measures of support for inequality including Social Dominance Orientation (SDO), a measure of individual differences in support for group‐based hierarchies. However, other studies have failed to replicate this association. In this article, we reexamine the link between upper‐body strength and support for inequality using 12 different samples from multiple countries in which relevant measures were available. These samples include student and locally representative samples with direct measures of physical strength and nationally representative samples with self‐reported measures related to muscularity. While the predicted correlation does not replicate for every single available measure of support for inequality, the overall data pattern strongly suggests that for males, but not females, upper‐body strength correlates positively with support for inequality.
The relationship between the general factor of intelligence (g) and handedness is investigated using a combined sample of 23511 respondents from three large databases: the NLSY'79 (US), NLSY'97 (US) and NCDS (UK). Dextrals - those who use their right hands were found to be 1.22 IQ points higher than sinistrals (left handers) after controlling for sex and age and correcting for sources of measurement error. To see if the association between IQ and handedness was strongest on the abilities that were the best measures of g, the method of correlated vectors was used to test for moderation. Across the three studies, g was found to very weakly negatively moderate the association between ability measure and handedness (ρ = -.023, K = 3, N = 23511), however in the NLSY'79, the coding speed subtest was an outlier in terms of the strength of its association with handedness. Its removal yielded indications of positive moderation in this dataset, which when aggregated boosted the overall vector correlation value to .539 (K = 3, N = 23511), suggesting that g might be an important moderator of this relationship. Secondary analysis of secular trend data on the changing percentage of sinistrals in Western populations indicates that overall, sinistrality has increased, entailing a g decline of .106 points over 150 years (.006 points per decade). The secular increase in sinistrality is consistent with other data indicating long-term declines in developmental stability and may stem from some combination of increasing mutation load and environmental stress in Western populations.
This article explores links between cultural individualism and the age at which adult-role responsibilities are assumed (the speed of maturation to adulthood). Across 43 years (1973-2015) within the United States, yearly indicators of individualism were positively correlated with later onset of work and family responsibilities (a slow life strategy). The same pattern appeared cross-culturally: Across 53 nations, cultural individualism was significantly correlated with slower maturation to adulthood. These links remained over time and cross-culturally when unemployment rate, an indicator of economic strength, was included in the model. Analyses including GDP showed mixed results, suggesting a complex relationship between economic indicators, individualism, and maturation to adulthood. Across nations and time, more individualistic cultures are also those with slower maturation to adulthood (a slow life strategy).
Cambridge Core - Comparative Politics - Cultural Evolution - by Ronald F. Inglehart
Physical attractiveness is an important social factor in our daily interactions. Scholars in social psychology provide evidence that attractiveness stereotypes and the “halo effect” are prominent in affecting the traits we attribute to others. However, the interest in attractiveness has not directly filtered down to questions of political behavior beyond candidates and elites. Utilizing measures of attractiveness across multiple surveys, we examine the relationship between attractiveness and political beliefs. Controlling for socioeconomic status, we find that more attractive individuals are more likely to report higher levels of political efficacy, identify as conservative, and identify as Republican. These findings suggest an additional mechanism for political socialization that has further implications for understanding how the body intertwines with the social nature of politics.
This book provides a new perspective on the association between religious beliefs and mental health. The book is divided into five parts, the first of which traces the development of theories of organic evolution in the cultural and religious context before Charles Darwin. Part II describes the major evolutionary theories that Darwin proposed in his three books on evolution, and the religious, sociological, and scientific reactions to his theories. Part III introduces the reader to the concept of evolutionary psychiatry. It discusses how different regions of the brain evolved over time, and explains that certain brain regions evolved to protect us from danger by assessing threats of harm in the environment, including other humans. Specifically, this part describes: how psychiatric symptoms that are commonly experienced by normal individuals during their everyday lives are the product of brain mechanisms that evolved to protect us from harm; the prevalence rate of psychiatric symptoms in the U.S. general population; how religious and other beliefs influence the brain mechanisms that underlie psychiatric symptoms; and the brain regions that are involved in different psychiatric disorders. Part IV presents the findings of U.S. studies demonstrating that positive beliefs about God and life-after-death, and belief in meaning-in-life and divine forgiveness have salutary associations with mental health, whereas negative beliefs about God and life-after-death, belief in the Devil and human evil, and doubts about one’s religious beliefs have pernicious associations with mental health. The last part of the book summarizes each section and recommends research on the brain mechanism underlying psychiatric symptoms, and the relationships among these brain mechanisms, religious beliefs, and mental health in the context of ETAS Theory.
What does it mean to label someone a fascist? Today, it is equated with denouncing him or her as a Nazi. But as intellectual historian Paul E. Gottfried writes in this provocative yet even-handed study, the term’s meaning has evolved over the years. Gottfried examines the semantic twists and turns the term has endured since the 1930s and traces the word’s polemical function within the context of present ideological struggles. Like “conservatism," “liberalism," and other words whose meanings have changed with time, “fascism” has been used arbitrarily over the years and now stands for a host of iniquities that progressives, multiculturalists, and libertarians oppose, even if they offer no single, coherent account of the historic evil they condemn. Certain factors have contributed to the term’s imprecise usage, Gottfried writes, including the equation of all fascisms with Nazism and Hitler, as well as the rise of a post-Marxist left that expresses predominantly cultural opposition to bourgeois society and its Christian and/or national components. Those who stand in the way of social change are dismissed as “fascist," he contends, an epithet that is no longer associated with state corporatism and other features of fascism that were once essential but are now widely ignored. Gottfried outlines the specific historical meaning of the term and argues that it should not be used indiscriminately to describe those who hold unpopular opinions. His important study will appeal to political scientists, intellectual historians, and general readers interested in politics and history. © 2016 by Northern Illinois University Press. All rights reserved.
Individual freedom looms large in political and ethical thought. Nevertheless, the theoretical foundations underlying modern liberalism continue to be contested by proponents and opponents alike. The Myth of Liberalism offers a unique contribution to this debate by following through on the often-underdeveloped suggestion that liberal principles are untenable because they are self-contradictory. By analyzing and ultimately refuting each of the proposed underpinnings of liberalism-liberty, equality, rights, privacy, autonomy, or dignity-Safranek concludes that contemporary liberalism is a myth: it is not a coherent political philosophy as much as a collection of causes masked by emotively potent political rhetoric. Safranek marshals thorough evidence to make the case that each of the allegedly fundamental liberal principles amount to the right to do as one desires. As a result, liberalism's proponents must offer some method or principle to mediate the inevitable conflict of desires. In fact, all liberal scholars invoke some form of John Stuart Mill's harm principle to proscribe unacceptable desires. But this leads to self-contradiction: because all acknowledge that harm can be psychological as well as physical, anyone suffers harm when his act is legally prohibited, as this denies him the object of his desires (liberty) for the sake of another's desires. Therefore any right advanced in the name of liberty contradicts that very principle. While finding inherent flaws in liberal justifications for personal liberty, including rights to same-sex marriage, abortion, and assisted suicide, Safranek reveals the consequences of the contemporary liberaldisdain for morality as a basis for law and constitutional rights. To correct for these shortcomings of the modern liberal notions of freedom, which are grounded in the passions, The Myth of Liberalism proposes an alternative way of safeguarding the human desire for liberty: a cogent retrieval of a pre-modern intellectual tradition that esteems reason and virtue. © 2015 The Catholic University of America Press. All rights reserved.
Author Summary
Daily interactions between individuals can influence their health both in positive and negative ways. Often the mechanisms mediating social effects are unknown, so current approaches to study social effects are limited to a few phenotypes for which the mediating mechanisms are known a priori or suspected. Here we propose to leverage the fact that most traits are genetically controlled to investigate the influence of the social environment. To do so, we study associations between genotypes of one individual and phenotype of another individual (social genetic effects, SGE, also called indirect genetic effects). Importantly, SGE can be studied even when the traits that mediate the influence of the social environment are not known. For the first time we quantified the contribution of SGE to more than 100 organismal phenotypes and genome-wide gene expression measured in laboratory mice. We find that genetic variation in cage mates (i.e. SGE) explains up to 29% of the variation in anxiety, wound healing, immune function, and body weight. Hence our study uncovers an unexpectedly large influence of the social environment. Additionally, we show that ignoring SGE can severely bias estimates of direct genetic effects (effects of an individual’s genotypes on its own phenotype), which has important implications for the study of the genetic basis of complex traits.
Generational IQ test score changes (i.e., the Flynn effect) have been shown to affect most measures of cognitive ability, although certain domains appear to be impervious. Because IQ test score changes have been found to differ between domains, evidence for specific domains is warranted to explain the nature, meaning, and causes of the Flynn effect. In the present cross-temporal meta-analysis, we investigated potential test score changes over time for ability emotional intelligence as assessed with a widely-used measure (i.e., the MSCEIT V2.0) based on data from 160 samples (N = 16,738) from English-speaking countries over a time-span of 15 years (2001–2015). We found no evidence for substantial generational test score changes in overall or branch (i.e., subscale) ability emotional IQ scores. Consistent with our expectations, test performance was substantially higher for women in most measures. Contrary to our expectations though, average performance of our participants was considerably lower than the performance of normative samples on all scales, thus raising concerns about the appropriateness of the current norms. In all, we argue that ability emotional IQ as measured with the MSCEIT V2.0 is largely unaffected by typical causes that have been proposed as responsible for the Flynn effect. This may be due to the close association of this construct with psychometric g (associations of MSCEIT V2.0 scores with cognitive task performance were modest in our data) on one hand and personality traits on the other hand, both of which have been shown not to be associated with test score gains.
Humans are biological systems and thus exposed to evolution, both in the past and in the future. Since evolution is recognized by life sciences as a real phenomenon, approaches to human health need to take it into account. This is done by the established discipline of evolutionary medicine. Evolutionary approaches to medical problems use past adaptations to indicate their mismatches with the present-day living conditions and suggest remediation of such mismatches. The aim of this chapter is to specifically focus on the most recent changes of human variation such as structural reduction of human morphology, changes in natural selection, or gene flow. Changes in reproduction and the ongoing coevolution of humans and pathogens are most relevant issues for clinical medicine too. All this research shall lead to a change in human health and disease definition. A new framework of disease classification, taking into account evolutionary rather than pure single-factored, mechanistic criteria, would be more up to date. Evolutionary medicine can contribute with a differentiated perspective to the understanding of human nature, its major medical challenges, and future.
In three nationally representative surveys of U.S. residents (N = 10 million) from 1970 to 2015, more Americans in the early 2010s (vs. previous decades) identified as Independent, including when age effects were controlled. More in the early 2010s (vs. previous decades) expressed polarized political views, including stronger political party affiliation or more extreme ideological self-categorization (liberal vs. conservative) with fewer identifying as moderate. The correlation between party affiliation and ideological views grew stronger over time. The overall trend since the 1970s was toward more Americans identifying as Republican or conservative. Older adults were more likely to identify as conservative and Republican. More Millennials (born 1980-1994) identify as conservative than either GenXers or Boomers did at the same age, and fewer are Democrats compared with Boomers. These trends are discussed in the context of social identification processes and their implications for the political dynamics in the United States.