Theodosius Dobzhansky: Observation

Theodosius Dobzhansky was geneticist and evolutionary biologist. Explore interesting quotes on observation.
Theodosius Dobzhansky: 18 quotes1 like

“Between 1937 and 1941, Dobzhansky went from being able to allow for the possibility of evolutionary mechanisms other than those he favored to a position in which everything that did not fit his definition of evolution was rejected.
In the midst of his outpouring of anger at and dismissal of Goldschmidt, Dobzhansky neglected to consider the fact that while Goldschmidt's systemic mutations may not have been observed, neither had the mechanisms of speculation that he, or anyone else, for that matter, had proposed. …it was and still is the case that, with the exception of Dobzhansky's claim about a new species of fruit fly, the formation of a new species, by any mechanism, has never been observed.”

Theodosius Dobzhansky

Jeffrey H. Schwartz, Sudden Origins: Fossils, Genes, and the Emergence of Species (1999)
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“According to Goldschmidt, all that evolution by the usual mutations—dubbed "micromutations"—can accomplish is to bring about "diversification strictly within species, usually, if not exclusively, for the sake of adaptation of the species to specific conditions within the area which it is able to occupy." New species, genera, and higher groups arise at once, by cataclysmic saltations—termed macromutations or systematic mutations—which bring about in one step a basic reconstruction of the whole organism. The role of natural selection in this process becomes "reduced to the simple alternative: immediate acceptance or rejection." A new form of life having been thus catapulted into being, the details of its structures and functions are subsequently adjusted by micromutation and selection. It is unnecessary to stress here that this theory virtually rejects evolution as this term is usually understood (to evolve means to unfold or to develop gradually), and that the systematic mutations it postulates have never been observed. It is possible to imagine a mutation so drastic that its product becomes a monster hurling itself beyond the confines of species, genus, family, or class. But in what Goldschmidt has called the "hopeful monster" the harmonious system, which any organism must necessarily possess, must be transformed at once into a radically different, but still sufficiently coherent, system to enable the monster to survive. The assumption that such a prodigy may, however rarely, walk the earth overtaxes one's credulity, even though it may be right that the existence of life in the cosmos is in itself an extremely improbable event.”

Theodosius Dobzhansky book Genetics and the Origin of Species

Genetics and the Origin of Species (1941) 2nd revised edition

“The evolution of life, and the evolutionary origin of mankind, are scientifically established as firmly and completely as any historical event not witnessed by human observers. Any concession to anti-evolutionists, suggesting that there are scientific reasons to doubt the facticity of evolution, would be propagating a plain untruth.”

Theodosius Dobzhansky

In a letter to J. Kunamoto, 1972.