Woe! That’s a tall order. I think that is a very personal question; everyone must come up with their own meaning. Of course, I have an opinion. I think the meaning in life is to discover ways to make the world for everyone to live. I feel a need to cooperate with other people in making the world a better place than when I entered it. Our evolutionary success follows from other animals that have strived in this world based on cooperation, such as bees, termites, monkeys, and apes. Groups of individuals cooperate in these animals and selfishness is not rewarded (on the whole).
It would be interesting if our purpose is to cooperate even further than other creatures have to create an organized, effective society. Some researchers have found that our ethics and moral behaviour has developed quite a bit over the centuries (think how bad it was when murder and assassinations prevailed across Europe) and it may be that we are headed in the right direction.