WHY THE DEFINITION OF EUSOCIALITY IS NOT HELPFUL TO UNDERSTAND ITS EVOLUTION AND WHAT SHOULD WE DO ABOUT IT

The evolution of altruism is the central problem of the evolution of e usociality. The evolution of altruism is most likely to be understood by studying species that show altruism in spite of being capable of '' selfish'' individual reproduction. But the definition of eusociality g roups together primitively eusocial species where workers retain the a bility to reproduce on their own and highly eusocial species where wor kers have lost reproductive options. At the same time it separates the primitively eusocial species from semisocial species, species that la ck life-time sterility and cooperatively breeding birds and mammals, i n most of which, altruism and the associated social life are facultati ve. The definition of eusociality is also such that it is sometimes di fficult to decide,what is eusocial and what is not. I therefore sugges t that, (1) we expand the scope of eusociality to include semisocial s pecies, primitively eusocial species, highly eusocial species as well as those cooperatively breeding birds and mammals where individuals gi ve up substantial or all personal reproduction for aiding conspecifics , (2) there should be no requirement of overlap of generations or of l ife-time sterility and (3) the distinction between primitively and hig hly eusocial should continue, based on the presence or absence of morp hological caste differentiation.