Increasing body and brain size constitutes a key macro-evolutionary pattern in the hominin lineage, yet the mechanisms behind these changes remain debated. Hypothesized drivers include environmental, demographic, social, dietary, and technological factors. Here we test the influence of environmental factors on the evolution of body and brain size in the genus Homo over the last one million years using a large fossil dataset combined with global paleoclimatic reconstructions and formalized hypotheses tested in a quantitative statistical framework. We identify temperature as a major predictor of body size variation within Homo, in accordance with Bergmann’s rule. In contrast, net primary productivity of environments and long-term variability in precipitation correlate with brain size but explain low amounts of the observed variation. These associations are likely due to an indirect environmental influence on cognitive abilities and extinction probabilities. Most environmental factors that we test do not correspond with body and brain size evolution, pointing towards complex scenarios which underlie the evolution of key biological characteristics in later Homo.
Labyrinth fishes (Perciformes: Anabantoidei) are primary freshwater fishes with a disjunct African-Asian distribution that exhibit a wide variety of morphological and behavioral traits. These intrinsic features make them particularly well suited for studying patterns and processes of evolutionary diversification. We reconstructed the first molecular-based phylogenetic hypothesis of anabantoid intrarelationships using both mitochondrial and nuclear nucleotide sequence data to address anabantoid evolution. The mitochondrial data set included the complete cytochrome b, partial 12S rRNA, complete tRNA Val, and partial 16S rRNA genes (3332 bp) of 57 species representing all 19 anabantoid genera. The nuclear data set included the partial RAG1 gene (1494 bp) of 21 representative species. The phylogenetic analyses of a combined (mitochondrial + nuclear) data set recovered almost fully resolved trees at the intrafamily level with different methods of phylogenetic inference. Phylogenetic relationships at this taxonomic level were compared with previous morphology-based hypotheses. In particular, the enigmatic pike-head (Luciocephalus) was confidently placed within the “spiral egg” clade, thus resolving the long-standing controversy on its relative phylogenetic position. The molecular phylogeny was used to study the evolution of the different forms of parental care within the suborder. Our results suggest that the evolution of breeding behavior in anabantoids is highly correlated with phylogeny, and that brood care evolved three times independently from an ancestral free spawning condition without parental care. Ancestral character state reconstructions under maximum parsimony and maximum likelihood further indicated that both bubble nesting and mouthbrooding have evolved recurrently during anabantoid evolution. The new phylogenetic framework was also used to test alternative biogeographic hypotheses that account for the disjunct African-Asian distribution. Molecular divergence time estimates support either a drift vicariance linked to the breakup of Gondwana or Late Mesozoic Early Tertiary dispersal from Africa to Asia or vice versa.
Speciation mechanisms remain controversial. Two speciation models occur in Israeli subterranean mole rats, genus Spalax: a regional speciation cline southward of four peripatric climatic chromosomal species and a local, geologic-edaphic, genic, and sympatric speciation. Here we highlight their genome evolution. The five species were separated into five genetic clusters by single nucleotide polymorphisms, copy number variations (CNVs), repeatome, and methylome in sympatry. The regional interspecific divergence correspond to Pleistocene climatic cycles. Climate warmings caused chromosomal speciation. Triple effective population size, Ne, declines match glacial cold cycles. Adaptive genes evolved under positive selection to underground stresses and to divergent climates, involving interspecies reproductive isolation. Genomic islands evolved mainly due to adaptive evolution involving ancient polymorphisms. Repeatome, including both CNV and LINE1 repetitive elements, separated the five species. Methylation in sympatry identified geologically chalk-basalt species that differentially affect thermoregulation, hypoxia, DNA repair, P53, and other pathways. Genome adaptive evolution highlights climatic and geologic-edaphic stress evolution and the two speciation models, peripatric and sympatric.
Informal social hierarchies within small human groups are argued to be based on prestige, dominance, or a combination of the two (Henrich & Gil-White, 2001). Prestige-based hierarchies entail the ordering of individuals by the admiration and respect they receive from others due to their competence within valued domains. This type of hierarchy provides benefits for subordinates such as social learning opportunities and both private and public goods. In contrast, dominance-based hierarchies entail the ordering of individuals by their capacity to win fights, and coerce or intimidate others. This type of hierarchy produces costs in subordinates due to its aggressive and intimidating nature. Given the benefits and costs associated with these types of social hierarchies for subordinates, we hypothesised that prestige and dominance cues are better recalled and transmitted than social rank cues that do not elicit high prestige or dominance associations (i.e. medium social rank cues). Assuming that for the majority of the population who are not already at the top of the social hierarchy it is more important to avoid the costs of dominance-based hierarchies than to obtain the benefits of prestige-based hierarchies, we further hypothesised that dominance cues are better transmitted than prestige cues. We conducted a recall-based transmission chain experiment with 30 chains of four generations each (N = 120). Participants read and recalled descriptions of prestigious, dominant, and medium social rank footballers, and their recall was passed to the next participant within their chain. As predicted, we found that both prestige cues and dominance cues were better transmitted than medium social rank cues. However, we did not find support for our prediction of the better transmission of dominance cues than prestige cues. We discuss whether the results might be explained by a specific social-rank content transmission bias or by a more general emotional content transmission bias.
Previous research has sought to explain the rise of right-wing populist leaders in terms of the evolutionary framework of dominance and prestige. In this framework, dominance is defined as high social rank acquired via coercion and fear, and prestige is defined as high social rank acquired via competence and admiration. Previous studies have shown that right-wing populist leaders are rated as more dominant than nonpopulist leaders, and right-wing populist / dominant leaders are favoured in times of economic uncertainty and intergroup conflict. In this paper we explore and critique this application of dominance-prestige to politics. First, we argue that the dominance-prestige framework, originally developed to explain inter-personal relationships within small-scale societies characterised by face-to-face interaction, does not straightforwardly extend to large-scale democratic societies which have frequent anonymous interaction and complex ingroup-outgroup dynamics. Second, we show that economic uncertainty and intergroup conflict predict not only preference for dominant leaders, but also prestigious leaders. Third, we show that perceptions of leaders as dominant or prestigious are not fixed, and depend on the political ideology of the perceiver: people view leaders who share their ideology as prestigious, and who oppose their ideology as dominant, whether that ideology is liberal or conservative. Fourth, we show that political ideology is a stronger predictor than economic uncertainty of preference for Donald Trump vs Hillary Clinton in the 2016 US Presidential Election, contradicting previous findings that link Trump‟s success to economic uncertainty. We conclude by suggesting that, if economic uncertainty does not directly affect preferences for right-wing populist leaders, other features of their discourse such as higher emotionality might explain their success.
Cultural evolutionary theories define prestige as social rank that is freely conferred on individuals possessing superior knowledge or skill, in order to gain opportunities to learn from such individuals. Consequently, information provided by prestigious individuals should be more memorable, and hence more likely to be culturally transmitted, than information from non-prestigious sources, particularly for novel, controversial arguments about which preexisting opinions are absent or weak. It has also been argued that this effect extends beyond the prestigious individual’s relevant domain of expertise. We tested whether the prestige and relevance of the sources of novel, controversial arguments affected the transmission of those arguments, independently of their content. In a four-generation linear transmission chain experiment, British participants (N = 192) recruited online read two conflicting arguments in favour of or against the replacement of textbooks by computer tablets in schools. Each of the two conflicting arguments was associated with one of three sources with different levels of prestige and relevance (high prestige, high relevance; high prestige, low relevance; low prestige, low relevance). Participants recalled the pro-tablets and anti-tablets arguments associated with each source and their recall was then passed to the next participant within their chain. Contrary to our predictions, we did not find a reliable effect of either the prestige or relevance of the sources of information on transmission fidelity. We discuss whether the lack of a reliable effect of prestige on recall might be a consequence of differences between how prestige operates in this experiment and in everyday life.