Oh, don't worry about that. Very frequently, small populations of organisms, especially those which reproduce rapidly, engage in interbreeding with blood-related members of the population; while this sort of breeding can produce deadly combinations of recessive traits, it also encourages genetic variation overall. Even if large numbers of offspring are unfit to survive, those that are may have changed in highly useful ways.
And I wouldn't expect anyone to find "planet" or "earth" inside the Bible except when referring to the earth beneath someone's feet; the Indo-European world believed that the earth was flat until after the Dark Ages (a good 4500 years or so, even by the Bible's reckoning).
Dog breeding is based on selecting traits of dogs that one wishes to replicate until reaching a living paradigm of that trait. Any dog breeder can tell you that. However, there are only seven actual species of the genus Canis: lupus, audustus, aureus, latrans, mesomelas, rufus, and simensis. The dog is only a subspecies of lupus. The different breeds of dog as we know them are subvariations of the supspecies Canis lupus familiaris.