This paper applies models of the onset of adolescent sexual intercourse using national data from Denmark and the USA. The model gave excellent fits to data on Danish Whites and a good fit to American Whites, but the model-fits for American Blacks and Hispanics were not as good. The weakness of the latter model fits may reflect either real processes that the model does not capture or problems in the reliability of adolescent sexuality data.

Unlike some psychiatric illnesses, criminal lifestyles are not reproductive dead ends and may represent frequency-dependent adaptations. Sociopaths may gain reproductively from their greater relative to nonsociopaths. This mating-effort construct should be assessed directly in future studies of sociopathy. Collaboration between biologically oriented and environmentally oriented researchers is needed to investigate the biosocial basis of sociopathy.

Howe et al. have mistaken gene x environment correlations for environmental main effects. Thus, they believe that training would develop the same level of performance in anyone, when it would not. The heritability of talents indicates their dependence on variation in physiological (including neurological) capacities. Talents may be difficult to predict from early cues because tests are poorly designed, or because the skill requirements change at more advanced levels of performance. One twin study of training effects demonstrated greater heritability of (...) physical skill after than before training. In summary, talents are real. (shrink)

Spatial and mathematical abilities may be “sex-limited” traits. A sex-limited trait has the same determinants of variation within the sexes, but the genetic or environmental effects would be differentially expressed in males and females. New advances in structural equation modeling allow means and variation to be estimated simultaneously. When these statistical methods are combined with a genetically informative research design, it should be possible to demonstrate that the genes influencing spatial and mathematical abilities are sex-limited in their expression. This approach (...) would give an empirical confirmation of Geary's evolutionary speculations. (shrink)