I'm currently trying hard to quit the forum habit, but dammit, here I go again...

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Go to youtube and look up talented little kids and tell me it's all the study of theory and work and practice that enables a seven year old to play drums like he's been playing for 20 years.
But nobody really IS saying that are they? Inventing an extreme and fairly silly point of view of view and then saying that it's wrong, doesn't make another opinion correct.
These examples PROVE beyond a shadow of a doubt that the "it" factor is a gift you are born with.
Nobody involved in research on these issues claims that everybody is born the same. That's clearly not true. Some are born taller, faster, smarter, and so on. Importantly, there is also more than one way to be 'smart' and not everybody’s brains have identical processing power. That’s beyond question. The serious debate is about what this mysterious "IT" actually is. Are people born with something as specific as a 'maths gene' or a 'music gene' or a 'language gene' or is it something more general that they then happen to apply to a particular area for long enough to achieve excellence.
There's no consensus on the details yet of course, but there does seem to be a lot of evidence for the idea that having 'talent' (or if you prefer, being a 'natural') has a lot to do with having an ability to concentrate - to lock in if you like - on a task in a very focused way, and then also being in the right time and place to find that special thing that engages your interest and motivates you to put the time in. It's not just putting a lot of hours in (which, one way or another, everybody still needs to do) it's more about how good the quality of your attention and focus is when you do it. Whether you use books, visual examples or your ears is probably less important than the quality of your concentration on the subject.
What you then use that ability for can depend on a number of factors, but opportunity is a biggie. Four year olds don't often go out and buy themselves a guitar, and the youtube 'prodigies' need both somebody to provide the equipment but also to assist and support them in being able to follow their passion for hours on end. So the so-called ‘natural’ violinist may equally have had the potential to be a ‘natural’ in some quite different area.
It's also true that many, if not most, of these child musical wonder-kids are never heard of again once the novelty of them being cute and precocious wears off. Some will succeed, some will go on to have unremarkable careers and some will switch focus and do well at something else. They don't all keep on track to gain genuine mastery, and they
definitely don't all write chart topping hit songs (just to drag it briefly back on topic...

).
Nor do the successful ones produce nothing but masterpieces. McCartney wrote some brilliant stuff, and some pretty dire offerings too. (Plus he was lucky enough to team up with Lennon, and a superb engineer/arranger in George Martin and was part of a very exciting creative scene and era, all of which do help). Ditto for any songwriter that I can think of - they all ‘naturally’ produced some pretty ordinary stuff as well as the gems (and that's only judging by the work they thought was good enough to record). B.B.King, who you mentioned, largely repeated himself for decades. Tiger Woods still loses golf games... and don't let's get started on Bill Gates' software....
The reverse is also true. Some people don't discover their passion until later in life. Perhaps I'm a 'natural' at something I don't even know about yet? I do know that I was a natural at Chinese for instance. Our brains seem to be 'hard-wired' for language, but not necessarily a particular one. Swap babies from different cultures at birth and they'll learn whichever one they're exposed to. I just never got the chance to hear or learn Chinese - so I can't speak or understand a word of it. But I did have the potential.
Most of all though, I can't think of any argument to support the idea that ignorance is ever better than knowledge. The whole 'natural' thing is all too often used as an excuse not to bother with any study, and that seems like a pity. McCartney knew plenty of theory when the Beatles were writing, he knew it from listening to hundreds of hours of Western music and picking up what worked, and from his own experimentation.
He just didn’t have all the language to go with it - although he certainly had some of it. I’m sure that he knew what concepts like ‘tuning’ and ‘chord progression’ and ‘melody, harmony and rhythm’ meant. That’s all part of what is somewhat misleadingly called “Theory”. I see music theory as intelligent written discussion about what works well in practice, not some airy-fairy imaginary stuff, and not a dreary strait jacket either.
I feel that I’m lucky enough to have been born with many what you might call ‘natural’ gifts, but I’ve also found that they can all be improved by doing some study. Learning doesn’t need to be dull, geeky or hard. I’ve worked in many areas, some of which seemed to come fairly easily to me, but I’ve not yet found one wasn’t improved by learning some tips from those who mastered it before. And that’s all “Theory” really is - it’s just the written distillation of the experiences of thousands of smart and accomplished people who went before us. It’s not compulsory to pay attention, but you’ll miss out on some very neat stuff if you do ignore it.
Somebody once said “I’ve been rich and I’ve been poor; believe me, rich is better”. So I say “I’ve been uneducated and I’ve been educated; believe me, educated is better”.
Cheers,
Chris