Living leads to death, purpose of living things is to pass life on. Nowadays we got too many distractions (technology etc.) to be actually sure what we suppouse to do in this world. Finding your right path is a good start. In past (like stoneage past), as u said, people had to be usefull or simply die... . There is actually a lot more to it but I am gonna play some Warcraft now and try to stay alive