Now you're just displaying what I wish was a very rare display of ignorance of anatomy and biology. Unfortunately, it is not.

Dude. If infant head led to large vaginas which led to a preference for big.dicks, evolutionarily speaking, dicks would have evolved to be, bare minimum, 10 cm in diameter as 10 cm is full dialation during birth.

But we know that baby heads areich bigger than that. They're an avg of 34.5 cm at birth. That's 13.5 inches in circumference.

Is your dick as big around as a grapefruit?

No?

Okay, so we can put that ridiculousness to bed.

Let me introduce you to a few biological facts.

Vaginas are specialized muscle tissue. They are special in that they are:

1. Elastic - they can return or recoil to their original shape when relaxed due elastic fibers within the structure.

2. The are extensible - the vagina can be stretched or extended (obvious by the fact that we can give birth at all if full dialation in only 10 cm)

3. They are excitable in that vaginas respond to stimulus.

Evolutionary work isn't the guess work you suggest. There's a lot more to it than that, but nice try.