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Producing single versus multiple births has important life history trade-offs, including the potential benefits and risks of sharing a common in utero environment. Sex hormones can diffuse through amniotic fluid and fetal membranes, and females with male littermates risk exposure to high levels of fetal testosterone, which are shown to have masculinizing effects and negative fitness consequences in many mammals. Whereas most primates give birth to single offspring, several New World monkey and strepsirrhine species regularly give birth to small litters. We examined whether neonatal testosterone exposure might be detrimental to females in mixed-sex litters by compiling data from long-term breeding records for seven primate species (Saguinus oedipus; Varecia variegata, Varecia rubra, Microcebus murinis, Mirza coquereli, Cheirogaleus medius, Galago moholi). Litter sex ratios did not differ from the expected 1:2:1 (MM:MF:FF for twins) and 1:2:2:1 (MMM:MMF:MFF:FFF for triplets). Measures of reproductive success, including female survivorship, offspring-survivorship, and inter-birth interval, did not differ between females born in mixed-sex versus all-female litters, indicating that litter-producing non-human primates, unlike humans and rodents, show no signs of detrimental effects from androgen exposure in mixed sex litters. Although we found no evidence for CYP19A1 gene duplications-a hypothesized mechanism for coping with androgen exposure-aromatase protein evolution shows patterns of convergence among litter-producing taxa. That some primates have effectively found a way to circumvent a major cost of multiple births has implications for understanding variation in litter size and life history strategies across mammals., (© 2016 Wiley Periodicals, Inc.)

Objective: To describe and understand the meanings that adolescents give to sexuality and how they are created and influence adolescents' reproductive health and sexual practices., Material and Methods: The research was conducted in three different regions within Bogoá city. Twenty focus groups were selected and 20 life stories of boys and girls between 10 and 14 years old were transcribed. From inductive and deductive categorization of the transcripts of the oral histories, an interpretative analysis was carried out in order to generate concepts and relations that comprise plausible hypotheses about the meanings that circulate in the adolescents' symbolic universe., Results: There are notable differences between the meanings that boys and girls give to sexuality, the ways in which such meanings are created, and the factors that contribute to its configuration. These findings imply dissimilar constructions related with reproductive and sexual health risks., Conclusions: The cultural constructions resulting from sexual differences that is, gender suggest the meanings that are given to sexuality in the groups studied and define ways of interacting with the social environment. Girls relate sexuality with reproduction and they experience it as negative. For boys, the possibility of a positive and pleasant experience of sexuality exists, marked by a context that encourages having sexual relations as a way of maintaining manhood.