Why females care more, theoretically speaking
Across the animal kingdom there is a strong trend for females to be more caring parents. Why? Researchers have now expanded upon previous theories to better explain why mothers and fathers differ in the effort they put into caring for young. Ref. Source 8n.
I read it but it does not really answer why it only gives a why not. It also depends on which part of the animal kingdom because as the article said there is nothing genetic that says women should take care of their young more than males. In fact in some species its the male that does all the work.