The major stages of a dog's life lead him from mating to gestation and birth, from nursing to weaning and the growth of the puppies. Then, it is old age and its consequences; the adult stage of the dog's life is dealt with all along.While the goal of reproduction is to produce puppies, the means to this end differ substantially among private owners and breeders. The owner of a pet or utility dog will occasionally allow a bitch to reproduce in order to obtain offspring having her characteristics although, contrary to popular belief, reproduction is not an absolute requirement for a dog's psychological or physiological health. In nature, access to reproduction in packs of wild dogs is highly dependent on an individual's status in the hierarchy, since the act of mounting is an indication of dominance. This can sometimes explain why mating occurs between dogs of incompatible temperaments.In contrast, breeders choose their sires and dams based on origin, progeny and genetic characteristics. The breeder often overcomes hierarchical obstacles by assisting and directing the mating between the selected dogs. If the dogs refuse to cooperate, he may even resort to artificial insemination to achieve his goal.