Facilitated variation is a new theory that has been presented by Marc W. Kirschner, a professor and chair at the Department of Systems Biology, Harvard Medical School, and John C. Gerhart, a professor at the Graduate School, University of California, Berkeley.[1]
The theory of facilitated variation addresses the nature and function of variation in evolution. Recent advances in cellular and developmental biology in the light of evolutionary biology shed light on a number of mechanisms for generating novelty. While the concept and mechanism of natural selection is well understood, the variation component of the evolutionary theory remains under-developed. Variation mechanisms such as mutations, genetic drift, and genetic flow have been studied and documented thoroughly. The theory of facilitated variation is an effort to illustrate that seemingly complex biological systems can arise with a limited number of genes, and a limited number of variation mechanisms.
This is accomplished by exploring the relation between the genotype and phenotype, specifically:
The theory can be summarized in the following points:
In the classical Darwinian view, a large number of successive mutations, each selected for its usefulness to the survival of the organism, is required to produce novel structures such as wings, limbs, or the brain. Alternatively, facilitated variation asserts that the physiological adaptability of core processes and properties such as weak linkage and exploratory processes enable proteins, cells, and body structures to interact in numerous ways that can lead to the creation of novelty with a limited number of genes, and a limited number of mutations.
Therefore, the role of mutations is often to change how, where, and when the genes are expressed during the development of the embryo and adult.
The theory challenges Irreducible complexity by explaining how mutation can cause unusual changes within a species. They explain how the individual organism can change from a passive target of natural selection, to a central player in the 3-billion-year history of evolution. By closing the major gap in Darwin’s theory Kirschner and Gerhart also provide a scientific rebuttal to modern critics of evolution who champion "intelligent design".
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