Humans are enormously variable. Just about every institution we have is subject to endless modification across cultures and throughout time. Even the underlying assumptions behind things we take for granted, such as democracy, money, or the use of money to undermine democracy, are subject to change from one country to the next. Of course, some institutions are more variable than others.
Sex, for example, is something humans can’t seem to get right. We keep changing the rules, coming up with new customs to regulate the act, changing those regulations on a cultural whim, and then declaring that there is only one right way to do it and punishing people who would dare to think the rules could be changed for any reason.