Sex differences in olfaction are well established, but explanations for those sex differences remain incomplete. One contributing factor could be individual-or cultural-level differences in exposure to odors. We tested whether frequent engagement with common sources of domestic odors (cooking, domestic animals, siblings) was linked to individual differences in olfactory reactivity and awareness among children in southern Namibia, and also compared study populations in southern Namibia and the Czech Republic using the established COBEL (Children's Olfactory Behaviour in Everyday Life) questionnaire. We did not find any effects of engagement with odor sources on olfactory behavior, but our results were consistent with usual olfactory sex differences in that girls scored higher than boys in measures of olfactory reactivity and awareness. Further, among the Czech children (but not among the Namibian children), odor identification abilities were positively linked to COBEL scores.Our data contribute to the literature that finds that sex differences in olfactory awareness are apparent across a diverse range of cultures and age groups.

The morphology of human female breasts typical for their permanent fat deposits appears to be unique among primates. It has been previously suggested that female breast morphology arose as a result of sexual selection. This is supported by evidence showing that women with larger breasts tend to have higher estrogen levels; breast size may therefore serve as an indicator of potential fertility. However, breasts become less firm with age and parity, and breast shape could thus also serve as a marker of residual fertility. Therefore, crossculturally, males are hypothesized to prefer breast morphology that indicates both high potential and residual fertility. To test this, we performed a survey on men´s preferences for breast morphology in four different cultures (Brazil, Cameroon, the Czech Republic, Namibia). As stimuli, we used two sets of images varying in breast size (marker of potential fertility) and level of breast firmness (marker of residual fertility). Individual preferences for breast size were variable, but the majority of raters preferred medium sized, followed by large sized breasts. In contrast, we found systematic directional preferences for firm breasts across all four samples. This pattern supports the idea that breast morphology may serve as a residual fertility indicator, but offers more limited support for the potential fertility indicator hypothesis. Future studies should focus on a potential interaction between the two parameters, breast size and firmness, which, taken together, may help to explain the relatively large variation in women's breast sizes.