The eclipse of Darwinism

Julian Huxley used the phrase "the eclipse of Darwinism" to describe the state of affairs prior to the modern evolutionary synthesis when evolution was widely accepted in scientific circles but relatively few biologists believed that natural selection was its primary mechanism. Historians of science such as Peter J. Bowler have used the same phrase as a label for the period within the history of evolutionary thought from the 1880s through the first couple of decades of the 20th century when a number of alternatives to natural selection were developed and explored - as many biologists considered natural selection to have been a wrong guess on Charles Darwin's part, and others regarded natural selection as of relatively minor importance. Recently the term eclipse has been criticized for inaccurately implying that research on Darwinism paused during this period, and Paul Farber and Mark Largent have suggested the biological term interphase as an alternative metaphor.

There were four major alternatives to natural selection in the late 19th century:

Theistic evolution largely disappeared from the scientific literature by the end of the 19th century as direct appeals to supernatural causes came to be seen as unscientific. The other alternatives had significant followings well into the 20th century; mainstream biology largely abandoned them only when developments in genetics made them seem increasingly untenable, and when the development of population genetics and the modern evolutionary synthesis demonstrated the explanatory power of natural selection. Ernst Mayr wrote that as late as 1930 most textbooks still emphasized such non-Darwinian mechanisms.

Evolution was widely accepted in scientific circles within a few years after the publication of On the Origin of Species, but acceptance of natural selection as its driving mechanism was much less. By the end of the 19th century criticism of natural selection had reached the point that in 1903 the German botanist, Eberhardt Dennart, wrote that "We are now standing at the death bed of Darwinism", and in 1907 the Stanford University entomologist Vernon Lyman Kellogg who supported natural selection had to admit "... the fair truth is that the Darwinian selection theory, considered with regard to its claimed capacity to be an independently sufficient mechanical explanation of descent, stands today seriously discredited in the biological world." Though he added that there were problems preventing the widespread acceptance of any of the alternatives, as large mutations seemed too uncommon, and there was no experimental evidence of mechanisms that could support either Lamarckism or orthogenesis. Ernst Mayr wrote that a survey of evolutionary literature and biology textbooks showed that as late as 1930 the belief that natural selection was the most important factor in evolution was a minority viewpoint with only a few population geneticists being strict selectionists.

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