Abstract

For the last 50 years the dominant stance in experimental biology has been reductionism in general, and genetic reductionism in particular. Philosophers were the first to realize that the belief that the Mendelian genes were reduced to DNA molecules was questionable. Soon, experimental data confirmed these misgivings. The optimism of molecular biologists, fueled by early success in tackling relatively simple problems has now been tempered by the difficulties encountered when applying the same simple ideas to complex problems. We analyze three examples taken from experimental data that illustrate the shortcomings of this sort of reductionism. In the first, alterations in the expression of a large number of genes coexist with normal phenotypes at supra-cellular levels of organization; in the second, the supposed intrinsic specificity of hormonal signals is negated; in the third, the notion that cancer is a cellular problem caused by mutated genes is challenged by data gathered both from the reductionist viewpoint and the alternative view proposing that carcinogenesis is development gone awry. As an alternative to reductionism, we propose that the organicist view is a good starting point from which to explore these phenomena. However, new theoretical concepts are needed to grapple with the apparent circular causality of complex biological phenomena.