Why is there no better answer?

Right and wrong comes from the ethics and morals of the society in which you are raised. Your friend's cannibals comment was extreme, but basically, he or she is right! Cannibals usually ate people because they thought they could take on the courage and, strength etc. of that person. Many so called primitive societies encourage between their young people before marriage. Some regard pregnancy as a wonderful sign that the girl is fertile. Girls marry and produce children as young as 12. So, if you have no beliefs, you will create your own idea of right and wrong, based on your teaching from your parents, or other adults you admire and respect.