Human social institutions can effect the course of human evolution. Just as climate-change, food supply, predators, and other natural forces of selec… - Peter Singer

The principles of ethics come from our own nature as social, reasoning beings.

It is easy for us to criticize the prejudices of our grandfathers, from which our fathers freed themselves. It is more difficult to search for prejudices among the beliefs and values that we hold.

It is now generally accepted that the roots of our ethics lie in patterns of behavior that evolved among our pre-human ancestors, the social mammals and that we retain within our biological nature elements of these evolved responses. We have learned considerably more about these responses, and we are beginning to to understand how they interact with our capacity to reason.