Ones interpretation on intelligence can be very different than another's.
Certainly genetics have something to do with it, the actual learning, perception and evaluation of data is more of an individual Nature rather than a preset sequence.
I do not think it is, if it was, then smart people would have smarter children, and by now we would have figured out everything.
Einstein referred to that as Gods Dice Game. The only absolute that I am certain of is change.
It is well proven that IQ is more genetic than anything. You can improve your score by a few points with hard work, but you can't pull yourself out of the general range. Intelligence is obvious from infancy where gifted kids are talking, walking and so on far earlier. They have not had time to learn it.
This depends on your definition of 'intelligence', of course, but here is a rough opening example. If you took an electrical engineer from 70 years ago -the best and most 'intelligent' in his field -and brought him to the present, he wouldn't be able to get a job. All of his knowledge of electrical systems would be outdated and if he, for example, admitted to not knowing what a microchip is, someone might say 'what, are you stupid?'. It may be incredible to believe, but even the most basically educated child of the 21st century is more 'intelligent' than Leonardo Da Vinci.
An 'intelligent' person is simply a person who has experience in many different areas and different tools for thinking with than you do. This is always determined by environment.
Now. Lets say you had a better brain than anyone else. Better connective tissue, faster responsiveness among neurones etc etc. All that would mean is that if you lived in Nazi Germany where nazi propaganda was your only influence in life, you would become a Nazi faster. Why? Because intelligence is a function of behaviour, and behaviour is determined by environment.
People often think of intelligence as some sort of internal quality. But there are not real internal qualities. If a person is having all kinds of complex and intense thoughts but can't get them out there at all not even to speak them then people will not call that person "intelligent" at least not until the person is able to express these things. Intelligence can be reduced to the expression of intelligence either in expressing knowledge of facts, sound evaluations, or through performance in managing data or physical objects in a way that produces functions recognized as indicating "intelligence".
I agree that genetics plays a large part in base intelligence. A persons raw ability to comprehend and process something. That I believe is entirely genetic however if you then take two people and place the one with more base intelligence in a worst school who will achieve more? In some cases of course the one with higher base intelligence over similar schools. However if you put these two people in vastly different schools the more naturally intelligent person does not stand a chance as he simply would not be taught the basic principles or formula the other was.
Now, while some people have gifts that others don't, everyone has a brain that can be expanded, and everyone has a potential to rise and be something great in their lives. It's all a matter of if they want to apply themselves in life. Someone are smart but waste their brain. It's sad really.