By the end of the 19th century, criticism of natural selection had reached the point that in 1903 the German botanist, Eberhard Dennert  , 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, asserted that "... 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."
A finais do século XIX, a crítica da selección natural chegara a un punto en que en 1903 o botánico alemán, Eberhard Dennert escribía que "Estamos presentes perante o leito de morte do darwinismo", e en 1907 o entomólogo da Universidade Stanford Vernon Lyman Kellogg, que apoiaba a selección natural, afirmou que "... a pura verdade é que a teoría da selección darwinista, considerada respecto a súa pretendida capacidade de ser unha explicación mecánica independentemente suficiente da descendencia, está hoxe seriamente desacreditada no mundo biolóxico."