Evolutionary Epigenetism: why do we still mention it?
I was at the lab (UOA) looking for bibliography on the Pliocene of Greece, when I found a copy of a rather old book on Evolutionary Paleontology (“Paléontologie Evolutive” of Jean Roger, 1976). It caught my attention, not only because it is one of my favorite subjects, but also because from what I’ve seen, Evolutionary Paleontology is and has been taught in different ways.
In the summary I found a lot of things that I’ve learned in relevant lectures, but there was one or two things that really got my attention. So here is my question: why do we still talk about evolutionary epigenetics?
Yes, in genetics classes we’ve learned that there are modifications of the genes after they’re transcripted into mRNA, and we’ve been told that this is one epigenetic mechanism. But, what is the relation between this and the evolutionary theories of epigenetics?
The book enlightened one first point, in the chapter on the mechanisms of evolution there is one part about the epigenetic theory. The author quotes P.P. Grassié: “an evolutionary necessity is the acquisition of new genes”. And later on we find another quote by S. Ohno (1970): “natural selection, much like a “policeman” is extremely conservative; if evolution depended only on this, from Bacteria could be obtained only many other forms of Bacteria. The creation of Metazoans, Fish, Mammals would be almost impossible without the creation of new genes.” No further explanation by the author. This is epigenetic evolution. The lack of further knowledge on genetics, genes duplication, the fact that natural selection is able to produce new genes, horizontal transfer etc. generated this idea that there are other mechanisms that produce diversity, independent from Darwin’s evolutionary theory. It does seem a little like an ensemble of speculations, because there is no specific proposition of a precise epigenetic mechanism. Also, and very wisely, the author does not take any sides, and waits for further research for an answer on the importance and the existance of such processes.
Modern epigenetics do not have the same evolutionary dimension.