High Notes

I would think that it's something you either can do or can't, I don't imagine any amount of voice training could have got Lee Marvin singing falsetto.

You may remember the film "Paint your wagon" in which he sang "I was born under a wand'rin star" from somewhere down in his boots.

It is my impression that the range of high notes for a person is fairly strictly determined by nature. Voice training, it is said, for a younger (or not) voice could improve the range.

Well, it's much more difficult to hit a high note when singing from your chest, so you might want to try singing in your head. Imagine climbing a staircase, each note is a different step. However, the note/s will not be as true.
I believe everyone can sing, it is a true expression of joy, but not everyone is able to sing like a prima donna, if your a bass singer, your hooped when it comes to hitting the higher octaves.