That's specious reasoning: something being learnt doesn't mean that people can't have an adaptation that aids, or inhibits, that particular learning.

Running isn't innate, we learn to do it. Most children do it. But some people lack the apparatus, some are just habituated against it, some are impaired in other ways. And, running is a defining characteristic of humans. (It's not a perfect analogy but I think it fits)

Not only that. From TFA:

  Prosopagnosia appears to be different from other 
  neurological memory problems because it doesn’t cause 
  any other issues with memory and isn’t always caused by 
  brain damage — as in my case, it can be developmental 
  and genetic. 

@schaefer: "Thanks."

To some extent, all visual processing is learned. See, for example:

https://www.reddit.com/r/todayilearned/comments/2apb6d/til_t...

But, yes, you need that part of your brain to be functional to start with as a prerequisite.