Some parts are copiable, but not the more abstract things like the human intellect, for lack of a better word.
We are not even born with what you might consider basic mental faculties, for example it might seem absurd, but we have to learn to see... We are born with the "hardware" for it, a visual cortex, an eye, all defined by our genes, but it's actually trained from birth, there is even a feedback loop that causes the retina to physically develop properly.
We should also consider the effects of trauma on those brains. If you’ve ever spent time around people with extreme trauma they are very much in their own heads and can’t focus outside themselves long enough to focus enough to learn anything. It definitely impacts intellectual capacity. Humans are social animals and anyone raised without proper socializing and intimacy and nurturing will inevitably end up traumatized.
We are not even born with what you might consider basic mental faculties, for example it might seem absurd, but we have to learn to see... We are born with the "hardware" for it, a visual cortex, an eye, all defined by our genes, but it's actually trained from birth, there is even a feedback loop that causes the retina to physically develop properly.