Historical records suggest that the political extremes—at both the “left” and the “right”—substantially endorsed conspiracy beliefs about other-minded groups. The present contribution empirically tests whether extreme political ideologies, at either side of the political spectrum, are positively associated with an increased tendency to believe in conspiracy theories. Four studies conducted in the United States and the Netherlands revealed a quadratic relationship between strength of political ideology and conspiracy beliefs about various political issues. Moreover, participants’ belief in simple political solutions to societal problems mediated conspiracy beliefs among both left- and right-wing extremists. Finally, the effects described here were not attributable to general attitude extremity. Our conclusion is that political extremism and conspiracy beliefs are strongly associated due to a highly structured thinking style that is aimed at making sense of societal events.

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Although genomic studies suggest that natural selection in humans is ongoing, the strength of selection acting on particular characteristics in human populations has rarely been measured. Positive selection on male wealth appears to be a recurrent feature of human agrarian and pastoralist societies, and there is some evidence of it in industrial populations, too. Here we investigate the strength of selection on male wealth, first in contemporary Britain using data from the National Child Development Study and then across seven other varied human societies. The British data show positive selection on male income driven by increased childlessness among low-income men but a negative association between personal income and reproductive success for women. Across cultures, selection gradients for male wealth are weakest in industrial countries and strongest in subsistence societies with extensive polygyny. Even the weakest selection gradients observed for male wealth in humans are as strong as or stronger than selection gradients reported from field studies of other species. Thus, selection on male wealth in contemporary humans appears to be ubiquitous and substantial in strength.

We examined associations between Five Factor Model personality traits and various outcomes of reproductive behavior in a sample of 15 729 women and men from the Wisconsin Longitudinal Study (WLS) and Midlife Development in the United States (MIDUS) survey. Personality and reproductive history was self-reported in adulthood (mean age: 53 years). High extraversion, high openness to experience, and low neuroticism were associated with larger number of children in both sexes, while high agreeableness and low conscientiousness correlated with larger offspring number in women only. These associations were independent of marital status. There were also more specific associations between personality and timing of childbearing. The findings demonstrate that personality traits of the Five Factor Model are systematically associated with multiple reproductive outcomes.

The existence of individual differences in personality can be puzzling from an evolutionary perspective. This paper offers a general framework for addressing this puzzle by combining insights from evolutionary, situational, and personality perspectives. To arrive at this framework, we first discuss three key evolutionary models for explaining personality variation: (1) selective neutrality, (2) mutation-selection balance, and (3) balancing selection. Second, we review four models of personality: (1) the General Factor of Personality, (2) The Big Two, (3) the Big Five, and (4) the six-dimensional HEXACO model. Third, we use situational affordances and trait activation perspectives to offer an integrative model of HEXACO domain-specific situational affordances. Finally, we use these perspectives to provide 18 propositions about situation, trait, and outcome activation (STOA) mechanisms which may help explain the maintenance of individual differences in six dimensions of personality.

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Many recent evolutionary psychology and human behavioral ecology studies have tested hypotheses by examining correlations between variables measured at a group level (e.g., state, country, continent). In such analyses, variables collected for each aggregation are often taken to be representative of the individuals present within them, and relationships between such variables are presumed to reflect individual-level processes. There are multiple reasons to exercise caution when doing so, including: (1) the ecological fallacy, whereby relationships observed at the aggregate level do not accurately represent individual-level processes; (2) non-independence of data points, which violates assumptions of the inferential techniques used in null hypothesis testing; and (3) cross-cultural non-equivalence of measurement (differences in construct validity between groups). We provide examples of how each of these gives rise to problems in the context of testing evolutionary hypotheses about human behavior, and we offer some suggestions for future research.Keywords Ecological fallacy . Cross-cultural research . Research methods . Simpson's paradox . Non-independence . Measurement equivalence Many hypothesis-testing techniques used by evolutionary behavioral scientists involve examining degrees of covariation between two or more variables and making inferences based on such relationships (e.g., analysis of variance, Pearson correlation). This approach may be applied to a number of different research designs that examine variation at different, hierarchically organized levels (e.g., individuals versus groups;

Despite clear advances in characterizing marine biofilms, details on their formation and species succession remain scarce particularly during the early stage of development. We investigated the microbial community composition and succession in coastal marine biofilms on plastic. Samples were collected over 75 days of immersion with strengthened samplings during the early stages of biofilm establishment. Biofilm composition was estimated using Illumina Miseq and microbial community interactions were assessed through microbial association network analysis. In silico analyses showed that primers used in most of previous studies considerably underestimated marine biofilm diversity. Unintentionally ignored so far, we showed that Flavobacteriia might be key actors in the functioning of marine biofilms. Gamma-proteobacteria from the genus Oleibacter strongly dominated microbial communities during the first hours of biofilm formation. These pioneer communities were quickly replaced by alpha-proteobacteria and Flavobacteriia. Bacterial communities exhibited fast temporal structure dynamics with taxa displaying rapid increases and declines. A total of 90% of operational taxonomic units (OTUs) were intermittent or ephemeral reinforcing the conclusion that marine biofilms are highly dynamics. With 2/3 of positive significant connections between bacterial OTUs, microbial biofilm communities appear to be more inclined to develop inter-specific cooperation rather than competition and might thus form sets of functional guilds with mutual metabolic exchanges.