I have heard and read a few things on the topic of a young baby looking more like the father than the mother as an evolutionary advantage, in order to convince the father to care for the baby. I have also read that this is just something that mothers tell their husbands as a way to convince the father to take more interest, but that it is all done subconsciously.
Whether the issue is that the baby actually looks like the father, or is just perceived this way, both perspectives are riding on the fact that if someone looks more like you, you take more of an interest in it.
In trying desperately to understand why my own father has a favorite child, it dawned on me. My fathers favorite, that he wont admit to, looks just like him.