From The Origins of Morality and Honor by the evolutionary biologist Edward O. Wilson, the world’s greatest ant expert:
Nevertheless an iron rule exists in genetic social evolution. It is that selfish individuals beat altruistic individuals, while groups of altruists beat groups of selfish individuals. The victory can never be complete; the balance of selection pressures can never move to either extreme. If individual selection were to dominate, societies would dissolve. If group selection were to dominate, human groups would come to resemble ant colonies.