Morals change too.
Not long ago it was perfectly all right to smack a child over the fingers or the rear end. But it was wrong to withdraw love, cheat or tell a lie.
Now it is morally wrong to smack a child but one does not talk much about the wrong in withdraw love or come with nasty remarks to a child or being sarcastic, something children don´t understand. A smack hurts for a moment, nasty remarks for a looooong time.
The experiment I would like to try is to raise a group of humans with no cultural biases or preconceptions (other then what they have themselves).
They experimented with babies as young as three months. How much cultural bias would you expect in them?
My daughter had a speaking vocabulary of 500 words by the time she was 1. I wrote down each word she said. She taught herself to read at 3.
My kids were saying distinct words at 6 or 7 months. The could produce 4 word sentences between 13 and 15 months.
While they were precocious, babies understand many words before their first birthday. They understand no and yes and many words involving food and eating as well as words for personal care.
this also means babies see violence as a legit punishment.