Paternal provisioning versus mate seeking in human populations

The Original Industrial Revolution. Did Cold Winters Select for Cognitive Ability?

Rushton and Jensen argued that cognitive ability differs between human populations. But why are such differences expectable? Their answer: as modern humans spread out of Africa and into northern Eurasia, they entered colder and more seasonal climates that selected for the ability to plan ahead, in order to store food, make clothes, and build shelters for winter. This cold winter theory is supported by research on Paleolithic humans and recent hunter-gatherers. Tools become more diverse and complex as effective temperature decreases, apparently because food has to be obtained during limited periods and over large areas. There is also more storage of food and fuel and greater use of untended traps and snares. Finally, shelters have to be sturdier, and clothing more cold-resistant. The resulting cognitive demands are met primarily by women because the lack of opportunities for food gathering pushes them into more cognitively demanding tasks, like garment making, needlework, weaving, leatherworking, pottery, and kiln operation. The northern tier of Paleolithic Eurasia thus produced the “Original Industrial Revolution”—an explosion of creativity that preadapted its inhabitants for later developments, i.e., farming, more complex technology and social organization, and an increasingly future-oriented culture. Over time, these humans would spread south, replacing earlier populations that could less easily exploit the possibilities of the new cultural environment. As this environment developed further, it selected for further increases in cognitive ability. Indeed, mean intelligence seems to have risen during recorded history at temperate latitudes in Europe and East Asia. There is thus no unified theory for the evolution of human intelligence. A key stage was adaptation to cold winters during the Paleolithic, but much happened later.

Temperature, Cultural Masculinity, and Domestic Political Violence

Cross-national data sets were used to examine the association between ambient temperature and internal political violence in 136 countries between 1948 and 1977. Political riots and armed attacks occur more frequently in warm countries than in both cold and hot countries, after controlling for effects of population size and density and levels of socioeconomic development and democracy. National differences on the cultural masculinity dimension, however, do account for this curvilinear temperature-violence association, in a subsample of 53 countries, suggesting that culture mediates the association. An explanation for this mediation in terms of Paternal Investment Theory is proposed.

Evolution, Culture, and the Five-Factor Model

Following areview of evolutionary approaches to the five-factor model (FEM), I develop a synthetic perspective that incorporates three levels of analysis: personality systems as universal psychological mechanisms, systematic group (i.e., gender, birth order, age, ethnic) differences that can be illuminated by evolutionary theory, and individual differences. At the level of universal mechanisms, personality systems are species-typical systems with adaptive functions in the human environment of evolutionary adaptedness. At the level of group differences, the evolutionary theory of sex, parent-offspring conflict theory, and life history are used to analyze sex, age, and ethnic differences in personality systems. At the level of individual differences, variation in personality consists of a range of viable evolutionary strategies for humans. Humans evaluate and act on the genetic and phenotypic diversity represented by this range of viable strategies to solve adaptive problems. Evolutionary perspectives on cross-cultural variation are noted and illustrated.

The Cognitive Differentiation-Integration Effort Hypothesis: A Synthesis between the Fitness Indicator and Life History Models of Human Intelligence

This article presents a potential synthesis between the fitness indicator and life history models of human intelligence through consideration of the phenomena of ability differentiation and integration. The cognitive differentiation-integration effort hypothesis proposes that these effects result from a life history tradeoff between cognitive integration effort, a mating effort component associated with strengthening the positive manifold amongst abilities; and cognitive differentiation effort, a somatic effort component associated with the cultivation of specific abilities. This represents one of two largely independent sources of genetic variance in intelligence; the other is mediated by general fitness and mutation load and is associated with individual differences in levels of ‘genetic g‘. These two sources (along with a common source of environmental variance) combine to give rise to a variety of cognitive phenotypes characterized by different combinations of high or low levels of ‘genetic g‘ and cognitive specialism or generalism. Fundamental to this model is the assumption that measures of life history speed ( K) and g are essentially independent, which is demonstrated via meta-analysis of 10 studies reporting correlations between the variables (ρ = .023, ns, n = 2056). The implications of the model are discussed in an evolutionary, ecological, and developmental context. Seven key predictions are made in the discussion which if tested could provide definitive evidence for the hypothesis.

A life-history model of human fitness indicators

Recent adaptationist accounts of human mental and physical health have reinvigorated the debate over the evolution of human intelligence. In the tradition of strong inference the current study was developed to determine whether either Miller's (1998, 2000a) Fitness Indicator Theory or Rushton's (1985, 2000) Differential-K Theory better accounts for general intelligence ("g") in an undergraduate university population (N=192). Owing to the lengthy administration time of the test materials, a newly developed 18-item short form of the Ravens Advanced Progressive Matrices (APM-18; Sefcek, Miller, and Figueredo 2007) was used. A significant, positive relationship between K and F (r = .31, p < .001) emerged. Contrary to predictions, no significant relationships were found between "g" and either K or F (r = -.09, p > or = .05 and r = .11, p > or = .05, respectively). Though generally contrary to both hypotheses, these results may be explained in relation to antagonistic pleiotropy and a potential failure to derive correct predictions for within-species comparisons directly from the results of between-species comparisons.

Evolution and proximate expression of human paternal investment

In more than 95% of mammalian species, males provide little direct investment in the well-being of their offspring. Humans are one notable exception to this pattern and, to date, the factors that contributed to the evolution and the proximate expression of human paternal care are unexplained (T. H. Clutton-Brock, 1989). The nature, extent, and influence of human paternal investment on the physical and social well-being of children are reviewed in light of the social and ecological factors that are associated with paternal investment in other species. On the basis of this review, discussion of the evolution and proximate expression of human paternal investment is provided.