A study of rabbits in the 1940s convinced many biologists that parthenogenesis -- reproduction without fertilization of an egg -- sometimes occurs in mammals  However, the study' s methods have since been shown to be flawed, and no other studies have succeeded in demonstrating mammalian parthenogenesis
Thus, since parthenogenesis is known to occur in a wide variety of nonmammalian vertebrates, there must be something about mammalian chromosomes that precludes the possibility of parthenogenesis
assumes that the methods used in a study of one mammalian species were flawed merely because the study's findings cannot be generalized to all other mammalian species