Gregor Mendel and the theory of species multiplication.

This article critically examines the revisionist interpretation, notably advanced by historian Robert C. Olby in 1979, that Gregor Mendel’s primary scientific aim was to investigate species multiplication through hybridization rather than the inheritance of traits. The authors analyze Mendel’s 1866 pea (Pisum) experiments and subsequent hawkweed (Hieracium) studies, concluding that Mendel did not adopt the strictest species concept nor primarily focus on speciation by hybridization in his Pisum work. They argue that Mendel regarded species and varieties as points on a continuum and that his Pisum experiments were more aligned with understanding trait inheritance and plant breeding, while his Hieracium work addressed constant hybrids considered as new species. The article also highlights that Mendel’s concluding remarks on constant hybrids as new species were likely added after his initial lectures and should not be taken as evidence of his original research motivation. Overall, the authors dispute Olby’s claim that Mendel’s Pisum experiments were designed to test species multiplication, emphasizing instead Mendel’s foundational role in genetics focused on inheritance patterns.