Richard Joyce writes in this 2007 book:
* We have evolved to categorize aspects of the world using moral concepts. Natural selection has provided us with a tendency to invest the world with values that it does not contain, demands which it does not make.
* Most parties agree that the origins of morality lie in the development of human cooperation. Few will object to the view that the human tendency to help each other in certain circumstances is a trait that has been naturally selected for. In the past few decades we have gained a clear picture of how helping traits can be favored by forces of natural selection – something which, perhaps, seems initially puzzling. The first step is helping behavior among family members. Why should an individual provide aid even for
his or her offspring? The answer is that offspring contain 50 per cent of an individual’s genetic material, and therefore (among certain kinds of creatures) those who look out for their young will enjoy an increased probability of having offspring in subsequent generations over those who do not. This will go for helping tendencies towards siblings as well, and, to a lesser extent, cousins, nephews and nieces, etc. (bearing in mind that several nieces/nephews are worth more, genetically speaking, than a daughter or son).
