This doesn't really answer your question, but I wanted to sketch out how I think about the blank slate (or something like it) since it seems like you're engaging sincerely with everyone here.
1. Since networks in general like to produce complex emergent behavior, and our understanding of brains and behavior and networks and emergence are still fairly limited, I deal with the uncertainty by looking for sane default positions (i.e., a position to hold in the absence of comprehensive evidence otherwise). I'm not sure if it's obvious from a distance, but in practice default positions are an exercise in intellectual humility.
2. I am working on a sort of razor. I don't know what to call it, yet. When it comes to animal-kingdom behavior, a good default position is to think of any observed behavior as being in the possibility space of the broader category until the evidence against this is overwhelming. If we see one crow use a tool, assume tool use is in the crow possibility space. If we see another corvid do it, assume it's part of the corvid possibility space. If we see some non-corvid avian do it, assume it's part of the avian possibility space. If we already know humans do it, assume this goes back at least to our last common ancestor with birds.
If all of the nurses anyone has ever seen are female humans, it is fair to think of the occupation as part of the female human possibility space. If anyone has seen any non-female human nurse, it is prudent to think of the occupation as part of the human possibility space. If anyone has seen a canine nurse, it is prudent to think of nursing as part of the mammalian or animal possibility spaces.
Once you know a behavior is in the possibility space, another good default position is: assume everything known to influence any other behavior in that possibility space is involved, until the evidence against is overwhelming. Why do humans choose to become a nurse or not? Assume family, society, friends, money, justice, punishment, education, teachers/mentors, status, media, profound experiences, mate-seeking, curiosity/interest, talent, chasing neurochemicals, instinct, charity, hormones, tradition, biology/neurology, etc. play a role.
While it's certainly possible that the male/female nursing delta is caused by genetic sexually-dimorphic destiny, the default position suggests it isn't prudent to give this any more weight than the other possibilities until some can be ruled out or sexual dimorphism is resoundingly demonstrated to be the primary causal factor.
3. As the evidence for human neuroplasticity continues to accumulate, it seems at least plausible that our brains are significantly more plastic than we currently realize.
Likewise, as the evidence for complex behavior like tool use and learning in non-human species accumulates (including fish, reptiles, and insects), it seems at least plausible that reasoning, problem-solving, plasticity, and flexibility are vastly older (and more basic/common) than we thought.
Given these, it seems like a decent default position to assume that complex/unique behavior is more likely (but not necessarily) plastic/flexible than hard-wired.