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Humans evolved right from the apes as Darwin described...and there were along the steps through uncertainty of thoughts in understanding the world around them. How it operates and how they had to survive. Initially, we revered the Sun, the mountain, the earth as Gods (the visible kind) and when those natural disasters occurred created a sense of fear in the human being. It has been adjudged as an act of Gods and they are not happy. They tried to figure out from there what went wrong. Few crooked minds took advantage of those natural signs formulated few customs to suit their needs. They created groups and blamed few people of their deeds for these natural disasters. They need someone to reason which is not in their intelligence to understand yet. I would think that is where SIN culture was evolved, I think.

Good question
Sin/guilt has both religious evolutionary social cultural factors involved .
The Christian belief of Original Sin the apple that the first Man Adam are against the command of God

Now what is sin- the sinful thought or sinful action
Who has decided a particular act or deed as sinful and particular acts as not sinful

Is the human thinking regarding Sin an apriori concept - something inbuilt in out very conscious or have we acquired the the idea of certain thoghts acts as sinful from society?

Do animals feel certain acts as sinful - we don't know

Among abrahamic religions the Ten Commandments state the acts that are Sinful

Carving an image of God
Adultery
Theft
Shedding the blood of your brother without reason among other things !!!

There are a set of Major and Minor Sins in Islam
Shirk - associating anyone with God is considered a Major Sin

Hinduism Buddhism has its set of Sins considered Sin ...like Lust anger greed but with variations ...

If someone can elucidate the story of sin sinful behaviour sinful thoughts in the early humans and if we can reflect on the present generation belief on what is a sinful act .... It would be great !!!

The sins of later generation post Jesus Christ Christian believers whose sins - for which Christ has already take the redemption