What is culture?

Wordweb dictionary defines culture as the “attitudes and behaviours that are characteristic of a particular social group.” I think this is a very straightforward definition but are the said attitudes and behaviours acquired or genetic? Also, is culture based on reason? Is it dictated by nature, since every culture evolved differently depending on the geographic location of a people? Is “deity” also a product of culture?

Since abnormal behaviour is behaviour that does not conform to the culture of one’s society, we would be correct to label one as “normal” if one woke up tomorrow morning and saw every neighbour walking backwards, and also immediately starts walking backward. That’s probably the new “normal.”

So in a society what is right is what is done by the majority not necessarily what is “good,” reasonable or sound. I think the advancement of a culture directly reflects how accommodating its actors are of reason. Now my last question to the reader: Do humans have a definite, eternal or unchanging nature? If so, what is this nature? I want to be enlightened.