Some philosophers have tried to base morality on human nature, but what does biology say about that?
In his 1945 public lecture 'Existentialism is a Humanism' Jean-Paul Sartre made a bold claim: for human beings, existence precedes essence. We exist, then we choose how to be. This is as opposed to a chair, for example, which is designed to fit a particular purpose and then brought into existence to fulfill that purpose. The chair has an essence that precedes it; it has a "chair nature" that it is created to conform to.