Moral relativism
Moral relativism rejects the existence of absolute morality and often argues that morality is a social construct that varies in different cultures. It has been criticized for a variety of reasons such as implying the absence of universal human rights and has often been used as a reason for rejecting various human rights criticisms.
Evolutionary psychology provides a non-religious explanation for morality as genetically influenced instincts that are evolutionary beneficial (in particular for a genetically related group). In many cases these instincts are universal and present in all societies (with the exception of psychopaths).
