Evolution of eusociality in termites.

A model is presented that demonstrates that asymmetries in relatedness such that individuals are more closely related to siblings than to offspring develop in diploid pedigrees under conditions of inbreeding. Given also certain incestuous conditions, the model predicts that eusocial-type helping behavior can be favored by natural selection. Three cases of the model are discussed along with implications for termite eusociality. Several aspects of termite biology, particularly the existence of replacement reproductives, are interpreted as evidence that termite eusociality may have arisen under the special conditions specified in the models.