OK I AM a neuroscientist ( well I'm a PhD student FWIW ) and I study language and music processing. I don't want to stifle conversation but I thought I'd drop in my US$.02 since this falls into my field.
Natural talent is a complex phenomenon. Some people are inclined towards music at a very young age, so they might pay more attention to it, even if they don't start playing an instrument right away. In a sense, that counts as practice. As far as why someone might be more inclined to pay attention to it, well that's not so well understood. I personally think the 10,000 hour rule is a good general rule. There will always be some contradictions but that's beside the point.
Mozart was regarded as a musical genius, but it's often forgotten that his father was a famous musical instructor, and the baby Mozart started lessons, like the day after being born (OK exaggeration
). Let's say he started lessons on his 2nd birthday. He could use his hands by then. If his dad had him practice 6 hours a day...So, by age 7 he would have hit his 10,000 hours! Thus, he's a pro at age 7. This sounds far-fetched, but there is evidence that this is what happened!
It's also important to note that the brain is much more plastic at a young age. Ever tried learning a language at age 40? It's HARD and you'll never sound totally natural at it. Yet, babies can pick up language automatically!! So if you start playing music at age 3 (a la Victor Wooten) then you'll have your 10,000 hours WAY earlier in life, and thus your brain will be naturally more wired to process music. It's like you'd be a native speaker of music. If you start later in life, your brain anatomy will still change, but the changes will be less and less extreme the later you start (and the less you practice).
As far as perfect pitch goes...there is a theory that we are all born with it but lose it. Chinese languages have a number of tones that are relevant to the meaning of the words (Mandarin has 4 Cantonese has 9 IIRC) so that, for example, 'bu' with a rising tone means something totally different from 'bu' with a falling tone. Most native speakers start their words at several distinct pitches depending on if it starts at a high/low/medium pitch. [Full disclosure I don't speak much Mandarin but I know the gist of it and I'm learning it bit by bit].
In English, our pitch usage in language is limited to the emotional meaning/sarcasm/question/statement domain, but in Chinese languages it changes the actual meaning of the word itself.
So...the idea is that for most Western languages, we don't really need to differentiate between exact pitches. We use relative pitch more. It doesn't make as much difference as it would in Chinese, and thus more Chinese children retain their innate absolute pitch. That's just a theory that's floating around, but it makes sense. If you USE that skill on a daily basis, then heck yeah it's going to stick around. If you never need to use it, the odds of retaining it are reduced.
There are always exceptions, but my view is that Nurture plays a MUCH bigger role on average than nature. We are all born with a huge potential and the more we use our brains (from the FIRST day of birth) the better we'll be at our many skills.
OK rant over.
