Rats exposed to ethanol throughout their gestation were found to have abnormally distributed mossy fibers in temporal regions of the hippocampus. This demonstrates that prenatal exposure to ethanol causes alterations in neuronal circuitry that persist to maturity. Such defects may play a role in the mental retardation often observed in children with fetal alcohol syndrome.

Evolution at multiple gene positions is complicated. Direct selection on one gene disturbs the evolutionary dynamics of associated genes. Recent years have seen the development of a multilocus methodology for modeling evolution at arbitrary numbers of gene positions with arbitrary dominance and epistatic relations, mode of inheritance, genetic linkage, and recombination. We show that the approach is conceptually analogous to social evolutionary methodology, which focuses on selection acting on associated individuals. In doing so, we (1) make explicit the links between the multilocus methodology and the foundations of social evolution theory, namely, Price's theorem and Hamilton's rule; (2) relate the multilocus approach to levels-of-selection and neighbor-modulated-fitness approaches in social evolution; (3) highlight the equivalence between genetical hitchhiking and kin selection; (4) demonstrate that the multilocus methodology allows for social evolutionary analyses involving coevolution of multiple traits and genetical associations between nonrelatives, including individuals of different species; (5) show that this methodology helps solve problems of dynamic sufficiency in social evolution theory; (6) form links between invasion criteria in multilocus systems and Hamilton's rule of kin selection; (7) illustrate the generality and exactness of Hamilton's rule, which has previously been described as an approximate, heuristic result.

Explaining altruistic cooperation is one of the greatest challenges faced by sociologists, economists, and evolutionary biologists. The problem is determining why an individual would carry out a costly behavior that benefits another. Possible solutions to this problem include kinship, repeated interactions, and policing. Another solution that has recently received much attention is the threat of punishment. However, punishing behavior is often costly for the punisher, and so it is not immediately clear how costly punishment could evolve. We use a direct (neighbor-modulated) fitness approach to analyze when punishment is favored. This methodology reveals that, contrary to previous suggestions, relatedness between interacting individuals is not crucial to explaining cooperation through punishment. In fact, increasing relatedness directly disfavors punishing behavior. Instead, the crucial factor is a positive correlation between the punishment strategy of an individual and the cooperation it receives. This could arise in several ways, such as when facultative adjustment of behavior leads individuals to cooperate more when interacting with individuals who are more likely to punish. More generally, our results provide a clear example of how the fundamental factor driving the evolution of social traits is a correlation between social partners and how this can arise for reasons other than genealogical kinship.

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