We have gone from protected to protector, assuming responsibility for those who are unable to fend for themselves. Altruism is an adult concept. It is adults who teach children to share their toys. As adults we share our own toys by building playgrounds for children, preserving the community's art and history, creating symphonies and theatres and libraries, raising money to fight disease. We put our knowledge and stores of data on the internet so that other people can use it too.
Adulthood brings with it perspective.
Babies who are hurting have nothing to gauge the pain by, and all pain gets the same howl of indignant protest. Adults understand that some pain is minor and short-term, and don't sweat the small stuff. We adults are people who have learned the art of the trade-off. We have learned to choose our battles carefully, because not every issue is important enough to spend the psychic energy on. There is a consistency of character to adults that is lacking in children and adolescents.