The last chapter is speculative in tone. The prospect of intelligent rats is grossly repugnant; so far, thank God, the tough immune system of the rat, inured to bacteria and filth, has rejected retroviral invasion. Indeed, the feral cat population seems to be driving these vermin toward extinction. Nor have opossums succumbed; indeed, marsupials of all kinds seem immune, making Australia a haven of a now-lost natural world. Whales and dolphins are endangered species; they seem unlikely to make a comeback even with the (as-yet-unknown) cetacean effects of chernobyling. And monkeys, which might pose a very considerable threat, are restricted to the few remaining patches of tropical forest and, like humans, seem resistant to the disease.