Most of my understanding of human behavior is lifted from evolutionary psychology. So I figure in that field there must be an exploration of this aspect of human behavior, but I am not sure what it is.
So what is a life of purpose and meaning, preferably from an evolutionary psychology point of view?
The concept itself seems to be service to other sentient creatures to help them achieve their goals (physical goals, psychological goals, social goals, personal goals, etc). Basically helping to maintain the mental, physical and social integrity of other sentient creatures that are part of your social unit.
So helping poor people obtain food, or helping the sick recover, or helping reunite families, helping to cure disease are all laudable goals that many people would find would give them purpose or meaning. If you can look back and see that if you had not been on this earth, then the integrity of other sentient creatures would be diminished then I guess you’ve lived a meaningful life.
Integrity is just a way to say staving off decay of order. Since biological creatures require huge amounts of energy input to maintain their sense of order and are extremely vulnerable, our social, biological and personal sense of self (as a healthy individual, a contributing member of society with status, an independent individual with an internal locus of control, someone with a healthy cognitive framework) can break down easily due to disease, trauma, setbacks, etc. Its like the movie Hellraiser said, Hell must be a place of pure chaos. Maintaining order in the chaos is hard. And getting a sense of meaning from helping other people maintain order seems to be the goal.
And from an evolutionary perspective, a tribe of 100 people where individuals obtained a sense of fulfillment from helping the other 99 members maintain their physical, social and psychological integrity against threats and entropy would have survival advantages over one where there was no sense of meaning. Just as long as people reciprocated the efforts. If not, people would feel cheap.
So what is a meaningless life? Is it a life where the only goal is to serve yourself? Or is there something else? Is a life meaningless if you life in a studio apartment, have no friends, no goals beyond yourself and only have your job and your hobbies?