Morals are the consequence of our nature. We are beings possessing something no other animal (so far as we know) does: the ability to communicate about that which is not immediate, tangible and real. We are also social animals, but unlike ants and bees, who cooperate extremely inflexibly in large numbers, we are restricted to flexible cooperation only in smaller groups, in which we can know something about all the others. UNLESS! And this is where that communication about the unreal comes in -- unless we can invent stories upon which we all agree. Nationalism, religion, money -- none of these things actually exist. We believe in money because everybody else believes in money. It has value for that reason and for no other reason. It is, in and of itself, not worth anything at all.
Our morality follows from the requirement for us to cooperate with others. In small groups (150 or fewer), we can do this because we know everybody, and moral behaviour is obvious -- it's what everyone expects of everyone else. In large groups -- towns, cities, countries, empires -- we do so only in the context of the stories we've come to share that define our group. What might be moral behaviour for an Aztec would be deeply puzzling to a Baha'i. What may be moral to a communist would be odd indeed to the committed capitalist.