We tend to see individual differences instead of human universals. Thus, when someone says the word 'intelligence,' we think of Einstein instead of humans.
The true sign of intelligence is not knowledge but imagination.
Einstein said 'your imagination is more important than intelligence,' and I have a very, very big imagination.
It's clearly possible for a something to acquire higher intelligence than its ancestors: we evolved to be smarter than our ape-like ancestors, and Einstein was smarter than his parents.
I was never top of the class at school, but my classmates must have seen potential in me, because my nickname was 'Einstein.'
Intelligence without ambition is a bird without wings.