It is become a common thing to say “ate the forbidden apple” as metaphor for “had sex”. Was sex the original sin of Adam and Eve?
Firstly i think what i hear is “ate the forbidden fruit” not an apple. I do not think the bible depicted any particular fruit in the book of Genesis and i do not know why the association with apple today.
“We may eat fruit from the trees in the garden. 3 But God did say, ‘You must not eat the fruit from the tree in the middle of the garden. Do not even touch it. If you do, you will die.’
The Lord already commanded them to “multiply and be fruitful”, and doing this would actually be a holy act since it would be in obedience to God who has given them seeds to fill the earth with offspring. So no, sex was not the original sin of Adam and Eve.
The sin was an act of disobedience and a refusal to admit guilt. Adam blamed Eve and indirectly God himself (to my understanding) when he said:
“It’s the fault of the woman you put here with me. She gave me some fruit from the tree. And I ate it.”
And when God asked Eve she blamed the serpent saying:
“The serpent tricked me. That’s why I ate the fruit.”
So the sin was not intercourse but disobedience. They had been commanded to have intercourse and fill the earth, so doing this cannot be sinful.