Follow this reasoning: We evolved, therefore we are animals.  If we are animals we have a particular pattern of behaviour as all other animals do.  The problem is that this isn’t the way we think in modern society.  It is embedded in our culture that we are above animals.  We are social beings, constructed by our culture.  This idea has been embodied in the way we think at least as far back as Aristotle, and it is enthusiastically buttressed in the Judeo-Christian tradition.  Time for a change?

“Do not fear to be eccentric in opinion, for every opinion now accepted was once eccentric.”  Bertrand Russell