"A Structuralist Analysis of Mendel's Two 'Hybridist' Theories and of their Intertheoretical Relationships"

LORENZANO, PABLO

Encuentro; 2017 Meeting. International Society for the History, Philosophy and Social Studies of Biology (ISHPSSB) & Associação Brasileira de Filosofia e História da Biologia (ABFHiB); 2017

International Society for the History, Philosophy and Social Studies of Biology (ISHPSSB) & Associação Brasileira de Filosofia e História da Biologia (ABFHiB)

The main problem Mendel faced and tried to solve was possibly that of "hybridism" ("can new species be originated by means of hybridization of preexisting species?") and not of inheritance. Based on a statistical analysis of his experiments, andseeking a "generally applicable law governing the formation and development ofhybrids" (Mendel 1865: 3), Mendel states "the law of development/evolutionfound for Pisum" (p. 32), which decomposes in "the law of simple combination of characters" (p. 32) and in "the law of combination of different characters" (p. 32). But neither of them isidentical to the laws usually attributed to him. Mendel's laws are formulated in terms of characters, not of "factors" or "genes". But, whenMendel tries to provide the "foundationand explanation" (Mendel 1865: 32) of the law offormation and development of hybrids, he does it in terms of the productionand behavior of egg cells and pollen cells, and, ultimately, in terms of thenature and behavior of what he calls "elements" (p. 41) or "cell elements" (p.42). However, Mendel's concept of cell element is different from Classical Genetics' concept of factor or gen. Mendel's elements are of a different nature of, and behave in a different way as, factors, alleles or genes. Furthermore, Mendel recognizes the existence not just of hybrids that behave like those of Pisum ‒ i.e. of "variable hybrids" ‒ but also of hybrids that "remain perfectlylike the hybrid and continue constant in their offspring" (Mendel 1865: 38) and "acquire the status of new species" (p. 40). Thus, Mendel supports "hybridism (in the narrow sense)", i.e.hybridism understood as establishing a mechanism of speciation, that is, of evolution.For all these reasons, it can hardly be said that Mendel had been a proponent, even less the first proponent, of Genetics. He was actually an excellent "hybridist". His hybridism consists of two theories: a first theory that moves on a level more "empirical" or "phenomenological" (according to Schleiden 1849: 141-146), which can be called "Mendel's theory of the development/evolution of hybrids" (DEH), and a second theory that moves on a level more "theoretical" (according to Schleiden 1849: 146-148), which can becalled "Mendel's theory on the cellular foundation of the development/evolution of hybrids" (CFH).The aim of this communication is to present ananalysis of these two theories and of their intertheoretical relationships, carried out within the framework of the so-called Metatheoretical Structuralism(Balzer, Moulines & Sneed 1987).