Female primates not only gestate and suckle young but are consistently more sensitive to and behaviorally attentive to offspring than are males. This is not to say that these differences are all hormonally or genetically determined—experiences do matter, as Conaboy argues. But nature has not left engagement in the associated behaviors to chance. Nor has it made maternal and paternal brains equally responsive to the associated experiences. In a review of brain imaging studies conducted while parents look at images or film clips of their children, Feldman noted that there is:
greater amygdala activation [associated with emotions] in mothers and greater cortical activation in fathers, suggesting that the hormones of pregnancy may chart a unique limbic path to parenting in mothers, which in fathers is constructed via cortical networks and active caregiving behavior.
Within-sex variation in parental behavior is found in both sexes, and in this case, more in men than in women. The variation in maternal and paternal attentiveness and responsiveness to children is partly heritable, but it is also related to the characteristics of parents’ individual children, to their past experiences, and to wider social mores (for instance, marriage rules). This is why, as Conaboy points out, some women describe parenthood as a fabulous and happy experience, while others find it physically and emotionally draining. There is nothing exceptional or unexpected about this variation. Biology will produce female-typical and male-typical biases and behaviors, including in parenting, as well as within-sex variation and cross-sex overlap.
For primates, a sex difference in physical size is a good indicator of the extent to which males focus on competing for mates rather than investing in offspring. If males are on average larger than females, this is generally associated with a polygynous mating system, whereby dominant males have offspring with many females and many low-status males never reproduce at all.
One study examined the patterns of grey and white matter in the brains of nearly 10,000 boys and girls and asked whether the sex of the child could be determined by these patterns. They can. The sex of 93 percent of the children was correctly identified.
Much remains to be learned about these differences which leaves plenty of room for legitimate debate. But there is no scientific room for the nonsensical idea that boys and girls and men and women are infinitely malleable and merely socially constructed products of the patriarchy or some other social system.
Source: The Ideological Refusal to Acknowledge Evolved Sex Differences