> because red hair color generally seems to occur more frequently in women than in men (shekar et al., 2008; frost et al., 2017; flegr and skorov, 2019), frost et al. (2017) suggested that prenatal estrogen, which is specific to female development, contributes to the expression of red hair during prenatal development and might be responsible for the sex difference in the frequency of redheadedness. conversely, a study by voracek et al. (2007) found that prenatal estrogen, as indirectly indicated by 2d:4d digit ratio, was not associated with lighter hair colors. still, that study did not examine an association between estimated prenatal estrogen and red hair color specifically, because red hair color was treated merely as one of the dark colors of hair. the sex difference in expression of red hair phenotype is, however, supported by a twin study which showed that in four of five twin pairs discordant in red hair color, the females were redheaded and males non-redheaded (box et al., 1997) > the second model suggests that higher sexual desire of redheaded women could be due to their switch from a slow to a faster life strategy, which could occur in response to poorer health. redheaded people, especially women, tend to have worse health (frost et al., 2017; flegr and skorov, 2019) and are more likely to suffer from certain diseases including cancer, endometriosis, and parkinsons disease (bliss et al., 1995; woodworth et al., 1995; missmer et al., 2006; gao et al., 2009; scherer and kumar, 2010; tell-marti et al., 2015; chen et al., 2017). it has been described how in reaction to impaired health, which reduces adult life expectancy and therefore also the length of the reproductive period, individuals tend to shift to a faster life history strategy, which manifests itself as earlier reproduction or having a higher number of children (waynforth, 2012; chua et al., 2017)
Brazil