I'm not sure about what you're asking, but taking a guess: I think that it's safer to have children raised by a larger amount of figures (primarily the parents, but also grandparents in a multi-generational household, other relatives if they exist, family friends - this would have been other people in the tribe or village traditionally - etc.).
Having all the responsibility fall on two mostly unsupervised, inexperienced people is fragile and "traditional" gender roles do not alleviate this.