Here's the problem with your assertion.

You're suggesting infants basically imprint on mothers for nurturing like baby birds because they lack the intellectual capacity for any kind of reasoning or inquiry.

I'm chuckling at that, but okay, let's assume that's more or less correct.

If that's the case, they don't need a father to instill confidence or teach them to navigate the world or whatever because by your own assertion, they're not smart enough to grasp what he's trying to teach them anyway.

Now, obviously no child is going to stay an infant forever. At some point their brain along with the rest of their body is going to develop enough to start exploring the world and will need some of that confidence, etc. But, they still need nurturing.

They're like little rubber bands. They stretch out exploring, and then need that safe place to snap back to. As time goes on, they stretch out further and for longer periods of time.

You're suggesting that during this period, the child needs two people to fill both those roles. That's certainly one way to do it. It's what has come about with gender sterotypes. But is it the only way to achieve the same end?

I'm suggesting that a more well rounded guardian who is not trapped in gender roles can switch successfully between the two and the child will not only accept it but may actually prefer it. I know a lot of kids raised by single parents for whom this is true, including my own.

Either way, it's still good to have the child socialized well with a broad variety of people so the child can see and observe many types of relationships and interactions.