Domesticated animals, such as dogs, have come into existence by the breeding of only the individuals of a wild species that are sufficiently tame. For example, if when breeding wolves one breeds only those that display tameness when young, then after a number of generations the offspring will be a species of dog. Ttherefore, all animals can, in principle, be bred for domesticity. Which one of the following, if true, most weakens the argument? ['In some animal species, no members ever display tameness.', 'Domesticated animals cannot be turned into wild species by breeding only those animals that display some wild characteristics.', 'In some animal species, wild members mate more frequently than tame members.', 'In some domesticated animal species, some members are much more tame than other members.']