From the “NYT”:http://www.nytimes.com/2007/09/18/science/18mora.html?8dpc.

bq. Where do moral rules come from? From reason, some philosophers say. From God, say believers. Seldom considered is a source now being advocated by some biologists, that of evolution.

Someone should tell “Brian Skyrms”:http://www.amazon.com/exec/obidos/search-handle-url/102-1247012-9760127?%5Fencoding=UTF8&search-type=ss&index=books&field-author=Brian%20Skyrms. I bet he’d have something interesting to say about this newly considered source.