The first question, of course, is whether there ever was such a creature as Man. At the moment, in the absence of positive evidence, the sober concensus must be that there was not, that Man, as presented in the legend is a figment of folklore invention.
the legend is a compendium of eight tales that are told as Dogs keep up the oral history of a far far away time and place before the time of Dog, a time of Man.
through the tales we are taken from the time when Man ruled the Earth, builds robots and Dog is man companion. later Man is able to communicate with Dog, colonizes Jupiter and abandons Earth to the peaceful and pacifist Dog.