A considerable number of publications have examined the effect of various geographical, life history, social, economic and political factors on homicide. However, few studies were interested in examining the effect of these forces in an integrated social biogeography of homicide. This study collected data for 172 nation-states from various publications and databases. Standardized Studentized residuals were extracted from a multilevel model examining the effects of geographical adjacency upon homicide rates. A general linear model was used, with the residuals, to observe the effects of physical, community, social, cultural, and cognitive ecology upon homicide. Two sequential canonical analyses (SEQCA) were conducted to determine the mediating effects among the ecological indicators with respect to homicide. In the SEQCA, we hypothesized physical ecology would lead to communal ecology, in turn leading to social ecology, subsequently leading to cognitive ecology, and ultimately to homicide. A parsimony test concluded that economic growth and inequality fully mediated the relationship between cognitive ecology and homicide residuals. Similarly, the effects of life history upon homicide were fully mediated by social ecology. This study suggests several social ecology factors appear to directly affect homicide; however, other aspects of ecology indirectly affected homicide through influences on social ecology. The effect of indicators of social ecology such as income inequality and the operational sex ratio indicate competition for resources is a significant force generating differences in homicide rates across populations. In conclusion, a suite of evolutionary pressures seems to influence homicide rates, but mainly in a sequential nature rather than simultaneously.

Simple models from the neutral theory of molecular evolution are claimed to be flexible enough to incorporate the complex effects of background selection against linked deleterious mutations. Complexities are collapsed into an "effective" population size that specifies neutral genetic diversity. To achieve this, current background selection theory assumes linkage equilibrium among deleterious variants. Data do not support this assumption, nor do theoretical considerations when the genome-wide deleterious mutation is realistically high. We simulate genomes evolving under background selection, allowing the emergence of linkage disequilibria. With realistically high deleterious mutation rates, neutral diversity is much lower than predicted from previous analytical theory.

Haldane’s Dilemma refers to the concern that the need for many “selective deaths” to complete a substitution creates a speed limit to adaptation. However, discussion of this concern has been marked by confusion over which features of substitutions produce limits to the speed of adaptation, what those limits are, and the consequences of violating speed limits. The term ‘substitution load’ has been particularly unhelpful in this regard. Here we distinguish different lines of reasoning that lead to speed limits, including one line of reasoning which has not yet been fully addressed. We then apply these lines of reasoning to a dataset measuring survival and fecundity of 517 different genotypes of Arabidopsis thaliana grown in eight different environmental conditions. We estimate highly permissive limits to the speed of adaptation in all environmental conditions. We also estimate that much higher proportions of deaths contribute to adaptation than were anticipated during historical discussions of speed limits.