There are two serious issues with this particular ambiguity.
First is that the quality of an answer you get is correlated with the quality of the question you ask. Having to guess at the meaning of an OP leads to confusion and often to battles over competing interpretations. And there are any number of threads in which all the guesses are wrong and everyone’s time has been wasted.
Even worse is the use of the word “valid” in the first place. Asking whether a particular avenue of investigation is valid science has been poisoned by groups like Creationists and global climate change deniers, who try to deliberately diminish science and scientists as frauds with agendas. Asking whether a mainstream hypothesis is valid has become equivalent to an accusation.
Sure, its use here might just be loose and sloppy thinking. Every once in a while we need to stop and point out that loose and sloppy thinking is the kind of ignorance that GQ is still here to fight. We do so in other threads about, say, physics or economics. It may not be appropriate as the very first response in a thread, but I waited until the question had been properly poked at in the hopes that the answers covered whatever it was that the OP had in mind. We still don’t know that, either.
Yeah, well, like I said, I’m of the opinion that the general stuff about how science works is not helpful in cases like this. It diverts too many threads into amateurish discussions of the nature of science, and it usually comes with a fair amount of bluster. It seems clear enough that “valid” was just a poor choice of words. No ignorance fought.
Are we really to the point that you feel compelled to do some deconstructionist drama queen Kabuki dance about how it’s impossible to understand what I meant by the term “valid”, in the context of a relatively straightforward, non-loaded layman’s question about the rigor of a theory that addresses (in part) the mechanism of human aging? Jesus.
I think most people conversant with the facts would agree that free radicals seem to be an important factor in the aging process. Most would also agree that telomere shortening seems to play a role, somewhere along the line. Most would also agree that these do not make up the whole picture, and there is much yet to be learned.
Interestingly, in some species at least, telomeres seem to be targets of recent strong natural selective pressure. They’re evolving rapidly, and the best guess is that they’re involved in the process of speciation. Centromeres too.