I have come to believe that morality develops in four broad stages across one’s life, each with a specific adaptive purpose.

Regardless of their global empathy, children are regularly focused on themselves. From a Darwinian perspective, they should be self-centered. A child’s primary goal is to survive childhood—a time when they are particularly vulnerable to accidents and disease.

Second comes teenage morality—focused on their peers. In our hunting-gathering past, teenagers needed to establish essential alliances with their comrades—individuals with whom they would travel, hunt, and gather throughout their lives.

Third is the moral code of parents, focused on their children.

Forth is the morality of older men and women. These people tend to focus on the future of the community. Post-reproductive people tend to concentrate (unconsciously) on building a world in which their DNA can flourish decades, even centuries, down the road.
~ Helen Fisher: Anatomy of Love: A Natural History of Mating, Marriage, and Why we Stray