Explore Evolution wrongly state that biologists originally maintained that the genetic code is absolutely universal (invariant); that this absolute universality was considered evidence for common descent; that this would be a reasonable inference because changing the code would be invariably lethal ("not survivable"); and finally, that the claim of universality fell apart in the 1980s with the discovery of variant genetic codes. Thus, the authors claim, the genetic code is not universal and the inference of common descent is in question and life must have "multiple separate origins." They cite physicist Hubert Yockey to justify the claim: "Some scientists think this is a possibility, saying that the evidence may point to a polyphyletic view of the history of life." (p. 59)
There are many problems with this argument, which is based on misunderstanding and misrepresentation of the available knowledge and of the scientific record.
First, contrary to the key assertion, scientists have been aware of natural genetic code mutants since at least the 1960s, and the actual molecular mechanism of some of these mutations (such as "suppressors of amber") was elucidated in both bacteria and yeast (Goodman HM, Abelson J, Landy A, Brenner S, Smith JD. (1968)...
...Second, the small number of organisms with variant genetic codes and the limited extent of the changes (involving a few codons at most) strongly support the view that these represent new variations of the "standard," universal code, as opposed to independently originated codes. Moreover, the known code variants themselves offer in many cases evidence for common descent, being shared by related organisms according to the established phylogenetic hierarchy,...