If we ask how creatures [bees] that act so elaborately against their private advantage can have evolved, the answer lies in their mode of reproduction. Most workers are sterile. The unit of selection is normally the whole community. Its prosperity depends on the efficiency of the workers. An uncooperative strain would simply revert toward the solitary life these insects started from and in which many would still remain.. So it is natural to understand their evolution, as we would that of a plant, without reference to the plans or wishes of the individual bees.

Beast and Man: The Roots of Human Nature (1979). 147.