Co-option and Constructive MutationsQUESTION: Co-option – Are constructive mutations possible?ANSWER:
Clearly co-option requires an abundance of constructive mutations in order to facilitate the development of novel functionality from previously existing macromolecules. However, while scientists once thought that there was ample evidence of mutations that were relevant to evolution, modern knowledge of molecular biology has completely undermined this. As biochemists unraveled the nature of genes and how they are expressed, it showed that the mutations the neo-Darwinists had found were due solely to the corruption of genes -- not the production of new ones. Therefore, whilst it was once thought that constructive mutations could arise readily, we now know otherwise.
Despite extensive efforts to generate and identify mutations, none has yet been found that offers constructive morphological change such as is required to fuel evolution. Even the mutations which confer resistance to insecticides etc, cited as evidence for advantageous mutations, are losing their impact as we uncover what is really happening at the molecular level.
At the heart of this absence of constructive mutations is the specificity and hence improbability of biological macromolecules. This was recognized to at least some extent fairly early on, but it was assumed that it could be overcome by macromolecules evolving at the molecular level in a similar way to morphological evolution; and, as the comparative amino acid sequences became available, at first these were seen as showing this sort of evolutionary change. It became apparent, however, that almost all of the inferred ‘evolutionary’ changes in sequence of biological macromolecules are in fact neutral -- most of the variation we see in amino acid sequences are of little if any selective consequence. Even if one is to accept the molecular phylogenies, the message they very clearly convey is that proteins (and RNA’s) were fully functional when they first appeared on the scene; all we see now are variations on a theme which was already successful; there is no evidence of a trial and error process by which a protein was progressively improved.