And this is the whole problem with taking a rational approach to something you know nothing about - you get the wrong answers because you are acting on the wrong information. As pointed out by param, there is a mountain of research on this subject which clearly indicates that a mother is essential to a child's development. A growing body of research shows that a present father is also very important. Nonetheless, we are adapted to the condition of the mother being present during our development, therefore it holds more weight than the father being present. Both parents being present improves things futher.