Perhaps societies have learnt through trial and error that  life is much better if run ethically.
Perhaps overall compassion on the weaker members of society is beneficial for all in the long term. 

This is aside from whatever any belief systems says or not

Frank wrote on Jan 1^st, 2024 at 10:24am:

Two things are obvious from your comments Frank...

Firstly you don't actually know what atheism is,
and/or how an atheist—like me—defines it.

You also don't understand the term "natural selection".

Natural selection is a simple mechanism that causes
populations of living things to change over time.   In
fact, it's so simple that it can be broken down into five
basic steps: variation, inheritance, selection, time and
adaptation. 

It has nothing to do with human morals and/or ethics,
and unequivocally nothing to do with any religious cult.

Consider Leviticus 20:13 before claiming what moral edicts
atheists take from the Abrahamic bible.  Hint—we don't
take any.  The bible is simply a work of fantasy fiction,
rooted [sic] in superstition, myths, fear, ignorance, and
oppression.

   If a man lies with a man as one lies with a woman, both
   of them have done what is detestable. They must be put
   to death; their blood will be on their own heads.