don't know why so many folks have their knickers knotted over this, since the truth is so obvious (or maybe that's just to anyone who's ever worked with livestock?) : genetics controls predisposition, while environment provides opportunity.
While (obviously) a person doesn't inherit actual skills, people often (but again obviously, certainly not always) inherit a set of genetic traits that predisposes them to more easily, more rapidly, and to a greater extent achieve a higher than average proficiency in a similar set of skills to those that one or both of their parents excelled at when compared to the average. Any one can learn to play the piano for example, but someone with the right predisposition is going to learn to do so with greater ease - and likely achieve a higher level of proficiency as a result - than someone who is tone deaf and has no inherent sense of rhythm. Of course, both of them have to be given an opportunity to learn to play or neither ever will - and of course, just because the parents don't have a predisposition for greatness at a particular skill doesn't mean that the child can't.
But as a general rule if you mate two exceptional racehorses, your chances of getting a foal that will win races is far far better than if you randomly selected a couple of cow ponies and hoped for the best.
With people, and skills that are more learned and less physical, environment plays a bigger role, but an inherited predisposition tends to influence environment, in that if one or both parents are musically inclined (for example), their child is going to be more likely to get the exposure that would bring forth the skills that they have a greater than average chance of having a natural proclivity toward.
The real argument isn't which is important, because both are - the hard question is to what extent do each limit the theoretical development, and because they tend to reinforce each other, to what extent each is responsible for the success (or failure) of any single individual to achieve a specific level of proficiency.
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