This article is very interesting and stimulated a great deal of discussion in our journal club. We were concerned, however, about the assertion that this sex ratio bias is adaptive. It seems extremely difficult to control for all possible non-adaptive causes. An interesting further test of this hypothesis may be to examine parents who came into wealth suddenly (such as lottery winners) and the relationship between sex ratios of their children before and after they became wealthy. Some discussion of the relatives ages of mothers would be helpful as well. One idea we discussed, "The Trophy Wife Hypothesis", was that wives of billionaires might be younger, and thus in better condition, than mothers in the average population. However, we anticipate that were there a clear relationship between maternal age and sex ratio it would have been mentioned previously in the literature.