The creation of our current social contract was a long and complicated process which has encountered endless amounts from resistance from one perspective or another. The humanist viewpoint would agree (partially) with your statement that some religious leaders and texts have helped to put ethics into words, inspite of their reliance on the supernatural to some degree.

Basic understanding of what makes a society successful is the primary motivation for humankinds current state of morality. Granted, vast numbers of humankind still reject all but the most barbaric forms of ethical behavior but thankfully these behaviorally challenged miscreants do not always rule the societies they are in. These people still function under the rule of religious intolerance and the barbaric belief that might determines ethics. These people still murder each other over idiotic disagreement and repress people of different belief systems (like homophobic rednecks vying for the lack of rights for homosexuals).

Given the exception of those who have no concept of a healthy society, we have come a long way. There have been many philosophers (some of which were religious) that had wisdom in their words and have helped us to organize semi-functional ethical outlooks.