Here we can see that mankind was made upright:
"So I turned my mind to understand, to investigate and to search out wisdom and the scheme of things and to understand the stupidity of wickedness and the madness of folly. I find more bitter than death the woman who is a snare, whose heart is a trap and whose hands are chains. The man who pleases God will escape her, but the sinner she will ensnare. 'Look,' says the Teacher, 'this is what I have discovered: Adding one thing to another to discover the scheme of things--while I was still searching but not finding--I found one upright man among a thousand, but not one upright woman among them all. This only have I found: God created mankind upright, but they have gone in search of many schemes'" (Eccl.7:25-29).
According to the false theory of Original Sin all people emerge from the womb totally corrupted in both body and soul.
I cannot understand why anyone would ever defend that deplorable theory, especially since it makes the LORD the author of sin. And who in their right mind would ever think that the LORD would hold infants responsible for the sins of Adam?