to the extent of my knowledge, that's actually not true (i don't know if you're going to like hearing this next bit...). supposedly everyone's born with it, but most people lose it due to lack of use.
How can someone be born with it?? You have to understand the concept of pitches and note names to be able to identify one that is played...and I know no one is born knowing that.
it's not in conjunction with the knowledge of theory, that's just not possible. but basically, infants up to a certain age have the intuitive capacity for it. it's just one of those things that contribute to a child's phenomenal learning capacity mentally... along with a whole lot of other stuff that it's necessary to unlearn in this world, because as you get older, it starts becoming a bad thing as it keeps you overly impressionable.
but i digress.
my esteemed fellow forum member Big Bad Bill
has gone on to say a lot of the same things as i have, but with the good scientific details to back it up rather than my weak statement of "i read somewhere". i recommend you direct your attention to his posts in this thread from now on if you want the whole story.