Environmental variability selects for large families only in special circumstances: Another objection to differential K theory

Rushton has argued that less predictable climates should select for r traits. However, because selection calls for maximizing the geometric mean rather than the arithmetic mean, and having small families could contribute to survival in adverse times, unpredictability should select for K characteristics. An alternative in which excess births provide an option on larger families is considered and rejected. Biological evidence from the Great Tit and other birds is used for illustration. This effect may explain why humans have such low conception rates. Several additional pieces of evidence for Millerʹs (Personality and Individual Differences, 17, 227–255, 1994) differential paternal investment theory are offered. Evidence for seasonality in prehistoric death rates is offered. Comparisons of fixation coefficients for Y chromosome genes vs mitochondrial ones suggest that polygyny has been more common in Africa than in Europe since prehistoric times. Additional evidence for racial differences in motivations for marriage and child bearing is offered. Higher Black expenditures on clothing is explained. In cold climates the greater importance of detecting a mateʹs deception is argued to select for higher intelligence.