Humans do not have such instincts that tell us not to kill other humans. We see that humans do kill others, sometimes by the thousands. Just as biological evolution resulted in instincts of animals, social evolution has resulted in human morals. Simply, societies that had moral laws and order were more successful and took over other societies that did not have such a social structure. Morals and ethics are just a means of survival of society, of our species. If humans did not have morals or ethics, we would start killing and steeling from each other and the species would not survive. Societal evolution is the source of morals and ethics. In my opinion, and I realize that its different from what most people have written, religion and religious books, such as the Bible or Koran, are not a source of morals. They are written records of ethics and morals of the societies that wrote them. They are containers of water (morals) rather then a spring (a source of them). Sense of right and wrong are passed from generation to generation from parents to children and from society to individuals, but again, those are not sources of morals or ethics, they are means of transfer of them through time.