Darwin's theory of natural selection (often summarized as "the survival of the fittest") was untestable in this sense, and therefore "almost tautological." Popper later changed his view, concluding that the theory of natural selection is falsifiable and that Darwin's own example of the peacock's tail had disproved one extreme variation of it, that all evolution is driven by natural selection. Although in 1978 Popper wrote that his earlier objection had been specifically to the theory of natural selection, in lectures and articles from 1949 to 1974 he had stated that "Darwinism" or "Darwin's theory of evolution" was a "metaphysical research programme" because it was not falsifiable. In fact he continued to express dissatisfaction with contemporary statements of the theory of evolution which focused on population genetics, the study of the relative frequencies of alleles (different forms of the same gene). Unfortunately some of the adjustments he proposed resembled Lamarckianism or saltationism, evolutionary theories that were and still are considered obsolete, and evolutionary biologists therefore disregarded his criticisms. In 1981 Popper complained that he had been misinterpreted as saying that "historical sciences" such as paleontology or the history of evolution of life on Earth were not genuine sciences, when in fact he believed they could make falsifiable predictions. Further confusion arose in 1980–1981, when there was a long debate in the pages of Nature about the scientific status of the theory of evolution. Specifically, the argument was on the factors influencing and nature of the unit of selection in the genome, with one side positing natural selection, and the other, neutral mutation. Neither of the parties seriously doubted that the theory was both scientific and, according to current scientific knowledge, true. Some participants objected to statements that appeared to present the theory of evolution as an absolute dogma, however, rather than as a hypothesis that so far has performed very well, and both sides quoted Popper in support of their positions. Evolution critics such as Phillip E. Johnson took this as an opportunity to declare that the theory of evolution was unscientific. Would anachronistic fossils disprove evolution? Richard Dawkins said that the discovery of fossil mammals in Precambrian rocks would "completely blow evolution out of the water." Philosopher Peter Godfrey-Smith doubted that a single set of anachronistic fossils, however, even rabbits in the Precambrian, would disprove the theory of evolution outright. The first question raised by the assertion of such a