I'm struggling to think of any way to test the hypothesis which is (A) practical and (B) accurate.
For example, suppose you sampled a group today and found an inverse-correlation between "good at recognizing many faces" and "good at recognizing written text"... That still wouldn't show that one facility grew causing the other to shrink, because maybe people are just born (or early-development-ed) with a certain bias.
For example, suppose you sampled a group today and found an inverse-correlation between "good at recognizing many faces" and "good at recognizing written text"... That still wouldn't show that one facility grew causing the other to shrink, because maybe people are just born (or early-development-ed) with a certain bias.