Argument

I wish to propose that the history of genetics reflects the history of the concept of reductionism in the life sciences. Reductionism is the thesis that explanation of laws or phenomena in one realm by those of another realm are always likely to be successful as explanations. By 1900 reduction of biology to the laws of chemistry and physics was not self evident: Although bottom-up preformationist explanations were largely inadequate for development, top-down epigenetic hypotheses often adopted metaphysical assumptions. Similarly, top-down theories of evolution as dependent on the accumulated impact of the past confronted those of bottom-up notions of fitness of specific traits that are relevant for future evolution. Mendel's 1865 methodological reductionist study of inheritance of traits was embraced in 1900 as evidence for reduction at the conceptual level. With the achievements of research of the mechanisms of inheritance, genetics became increasingly genocentric in its explanatory arsenal of development, and accordingly it was in conflict with the top-down, life-as-organized-systems' notions of embryology. Similarly, evolution was conceptually reduced to changes of gene-frequencies in populations. It was, however, precisely the increasing attempts to ground the bottom-up approach at the molecular level that eventually pushed conceptual reductionism to its crisis. Modern developments of molecular and computational methods finally forced, or allowed, researchers to apply bottom-up methodologies to top-down systems' analyses.