First I thought it was a weird question but everytime I see it the more profound it becomes.
The question isn't very accurate because there are a lot of factors that is involved with people's ability to become a GM or not.
Is the question asking about people as they are today with all their tendencies, experiences, and what else a person is comprised of?
Or does the question assume that people are willing to do whatever it takes to change their outlook on life, leave their "former" life to start a new one surrounding chess, change their mindset, maybe change diet, go see a life coach, maybe hypnosis if needed, etc?
I hope people can see that most people are not willing to make these changes to become a GM. But does this mean they aren't able to do so? I do believe that if people were willing to change much if not most of what they "are" that people indeed would be much more likely to reach a GM title. But the thing is some people order pizza delivery even tho the pizzaria is just across the street. xD
oh god hypnosis my biggest nightmare. But i like your post, very interesting.
I would think that most people of above average intelligence, given the motivation and training, and an early start could become a master, but there's a long way between a master and a grand master.