In today’s Nature, we find this article:
“Synonymous mutations in representative yeast genes are mostly strongly non-neutral.”
They investigated what effect “synonymous, nonsynonymous and nonsense” mutations involving “21 endogenous genes” would have on yeast. The fitness levels of synonymous and nonsynonymous fell in equal (though not ‘identical’) measure–around 75%.
I don’t have access to the article itself, only the abstract. The abstract begins thusly:
Synonymous mutations in protein-coding genes do not alter protein sequences and are thus generally presumed to be neutral or nearly neutral[1,2,3,4,5]
1 through 5 are citations. Who are they: Kimura, King and Jukes, Nei and Kumar, Li and Dan Graur. The heavyweights of neutral theory.
The abstract ends:
The strong non-neutrality of most synonymous mutations, if it holds true for other genes and in other organisms, would require re-examination of numerous biological conclusions about mutation, selection, effective population size, divergence time and disease mechanisms that rely on the assumption that synonymous mutations are neutral.
In the Phys.Org press release, one of the authors is quoted saying:
“Since the genetic code was solved in the 1960s, synonymous mutations have been generally thought to be benign. We now show that this belief is false,” said study senior author Jianzhi “George” Zhang, the Marshall W. Nirenberg Collegiate Professor in the U-M Department of Ecology and Evolutionary Biology.
“Because many biological conclusions rely on the presumption that synonymous mutations are neutral, its invalidation has broad implications. For example, synonymous mutations are generally ignored in the study of disease-causing mutations, but they might be an underappreciated and common mechanism.”
I can hardly wait to see what Larry Moran says at his Sandwalk blog.
I have often made fun of those who hold to the Neutral Theory in the non–Kimuran sense. My problem with the idea of everything being ‘neutral’ was that, hypothetically, anything can become anything. There’s no start nor finish to this process. I thought it was extravagant; instead, it was just wrong. Modern techniques–the use of Crisper to make mutant genes, has now allowed us to see how NT is a ‘dead-end.’ We can only hope that evolutionary biologists can see this. But there’s really no reason for such hope, is there?
The authors tell us that there’s no reason to believe that what they found in yeast won’t be found in other eukaryotic species, but that this will have to be tested to confirm that this ‘dead-end’ generally holds. I’ll bet on it holding in most families with few, if any, exceptions. We’ll see. Science progresses (while Darwinism ebbs).