Ernst Haeckel formulated his biogenetic law, famously stating that ontogeny recapitulates phylogeny, in 1872. The Russian evolutionist Alexei Sewertzoff, and the Swiss-born zoologist Adolf Naef were among those who revised Haeckel’s law, thus changing the course of evolutionary theory and of developmental biology. Although Sewertzoff and Naef approached the problem in a similar way and formulated similar hypotheses at a purely descriptive level, their theoretical viewpoints were crucially different. While Sewertzoff laid the foundations for a Darwinian evolutionary morphology and is (...) regarded as a forerunner of the modern synthesis, Naef was one of the most important figures in “idealistic morphology”, which is usually seen as a type of anti-Darwinism. Both Naef and Sewertzoff aimed to revise Haeckel’s biogenetic law and came to comparable conclusions at the empirical level. This paper is an attempt to explain how their fundamentally different theoretical backgrounds influenced their views on the relationship between ontogeny and phylogeny. (shrink)

The dichotomy between ‘typological thinking’ and ‘population thinking’ features in a range of debates in contemporary and historical biology. The origins of this dichotomy are often traced to Ernst Mayr, who is said to have coined it in the 1950s as a rhetorical device that could be used to shield the Modern Synthesis from attacks by the opponents of population biology. In this two-part essay, I argue that the origins of the typology/population dichotomy are considerably more complicated and more interesting (...) than is commonly thought. In the first part, I argued that Mayr's dichotomy was based on two distinct type/population contrasts that had been articulated much earlier by George Gaylord Simpson and Theodosius Dobzhansky. Their distinctions made eminent sense in their own, isolated contexts. In this second part, I will show how Mayr conflated these type/population distinctions and blended in some of his own, unrelated concerns with ‘types’ of a rather different sort. Although Mayr told his early critics that he was merely making “a temporary oversimplification,” he ended up burdening the history and philosophy of biology with a troubled dichotomy. (shrink)