Significant progress was made in 1964 when Hamilton formulated the inequality in kin selection known as Hamilton's rule, which showed how eusociality in insects (the existence of sterile worker classes) and many other examples of altruistic behavior could have evolved through kin selection.
Fixéronse progresos significativos en 1964 cando Hamilton formulou a desigualdade da selección de parentesco coñecida como regra de Hamilton, que mostraba como a eusocialidade nos insectos (a existencia de clases de obreiras estériles) e moitos outros exemplos de comortamento altruísta puido ter evolucionado por selección de parentesco.