It tends to become a touchy subject when you suggest that brain functionality differs between people but we seem to blindly accept that some people make better athletes than others.
It is particularly hard because you can't simply look at somebody and make any sort of judgement about ones mental abilities and there sometimes is no rhyme or reason why one person is more creative, or smarter than the other.
For me, I am a strong believer that brain functions are much like those of our physical counterparts. While the majority of people can all train the body up to run 1, 5, or 10 miles or more some people will simply have to exert less effort and be able to run further or faster than others. The same goes for brain functions. We can all be "good" in math, science, reading excreta... But only a subset of us will be experts in those subjects or even all of those subjects.
I think there is a lot to be studied how how early brain development can push the boundaries for the given set of hardware you are born with. But at some point I think you are mostly locked into what you have.
This is a hard topic to even begin to study. Because while two people may be able to preform the same mental functions we don't have a good way of judging amount of effort, and prep time required. For example, somebody who is just introduced to a new consept and can preformed the mental functions within minutes of introduction vs somebody who can preform the same mental functions but required 2 years of practice. The two people have very different cognitive capabilities, and you could argue one is smarter than the other.
As for the notion that we are not all the same. Please don't take that as we should be treating each other different based off skills. I think with regards of us all being human we all deserve the same level of respect and opportunity in life. My interest in this subject is based on the notion that we could have happier lives if this sort of subject was less taboo and we could explore making life decisions based off our actual aptitude. I would much rather work with people, and do a job that I found "easier" every day than a job that I could do that I found "hard". While that is a very black and white statement that is not to mean that I don't want a challenge, but it does mean that I don't want to constantly be struggling.
I see this in the world already. Where people take jobs they hate, because their aptitude is simply low for that line of work. Where everything is constantly a uphill battle. I can't help to wonder how much better their life would be had they picked a different job where the work came more easy and maybe even considered fun to them. I was lucky to find a job where there is just enough hard stuff to keep me busy, but the bulk of the work I find easy. I think a lot of people who found their way into software experience this. Meanwhile I have friends who can't wait till the work day is over and generally hate their job and complain about how hard it is.
So simply put, some people are more creative, or smart or any other attribute because we are all different, and had different experiences during critical brain development times in life. I think the expectation that everybody would be the same -- or even have the same aptitude on any given mental exercise would be weird -- unless we were all clones.