 Historical studies have revealed that only rarely did members of the scientific elites accept and develop Darwin’s theories exactly as they were presented in his texts. Statistical studies on the reception by the scientific community in England in the first decade after the publication of the Origin have shown a complicated picture in which there was neither wide-spread conversion of the scientific community to Darwin’s views, nor a clear generational stratification between younger converts and older resisters, counter to Darwin’s own predictions in the final chapter of the Origin (Hull et al. 1978). These studies also reveal a distinct willingness within the scientific community to separate acceptance of Darwin’s more general claim of species descent with modification from common ancestors from the endorsement of his explanation of this descent through the action of natural selection (Bowler 1983, 2013a). To utilize the categories of a Lakatosian “research program” analysis of scientific theories in their historical extension, one can distinguish between a “hard core” of defining central assumptions, a “protective belt” of auxiliary hypotheses that protect this central core from refutations, and a “positive heuristic” of applied research applications that are subject to continued revision and even refutation (Lakatos 1970). With these distinctions in mind, it is difficult to claim that anything more than the belief in descent from common ancestry was maintained by a broadly international scientific community at the “hard core” level in the period between 1870–1930. This meant that the historical impact of Darwin’s theories on the professional scientific community must consider the important deviations from his own formulations (Bowler 1983, 2003).