It is the dominant motive of all productive activity. No doubt in part it is. The individual must make sure he himself survives before the species can survive. And the so-called profit motive itself is seldom solely selfish. In a primitive society the unit is seldom the individual but the family, or even the clan.
Division of labor begins within the family.
In the clan or the wider group there is even more minute subdivision and specialization of labor. There are farmers, carpenters, plumbers, architects, tailors, barbers, doctors, lawyers, clergymen, and so ad infinitum. They supply each other by exchanging their services. There develops an immense system of voluntary productive cooperation and voluntary exchange. And in selecting this he is guided by the relative rewards in this occupation, by its relative ease or difficulty, pleasantness or unpleasantness, and the special gifts, skills, and training it requires.