Mutations would eventually lead to the extinction of a species

The error here is the word ‘the’ in the phrase ‘the two ways’. Kondrashov uses the word ‘including’ thus we left with the question as to whether or not the full article contains further possibilities. I would also point out that at least one of Pro’s ‘critiques’ contained little to no mention of Kondrashov’s answers. I’m also going to break from my formatting right now. Overall, this debate rests on two foundations: Muller’s ratchet. Or, more accurately, the existence of something like it (in this case, a ratchet that can be turned backwards as well as forwards) that affects sexual populations. That this ratchet-like process will move faster forwards rather than backwards and thus cause all species to go extinct (not just humans). Without these two foundations, or pillars, the argument collapses. It’s fairly easy to knock down the second pillar in the case of humans. The chance that we would use some form of eugenics to keep ourselves from going extinct is hardly remote, whether it is unethical is another debate entirely (while I’m acutely aware of the slippery slope, I regard it as preferable to allowing a process of extinction that would result in great pain and suffering for many generations along the way). But humans are a special case, since we have genetic knowledge and gene sequencing. Rather, let’s look at a wild population of species <em>X</em>. It can be pretty much identical to us, but it doesn’t have our technology and medicine. This ratchet-like mechanism demands that rate h, the rate of accumulation of harmful mutations, outpaces rate b, the rate of beneficial mutations (neutral mutations, which are, for reasons I’ve already stated, pretty common, are ignored here, as are environmental-dependent ones). Moreover, it demands that this be, at the very least, a highly common occurrence, if not a universal one. Now, to say that this ratchet-like mechanism exists and will cause the extinction of species as opposed to survival or evolution is a pretty extraordinary claim, and thus requires some pretty convincing evidence. Pro says that he has, and I’ll let his arguments stand for themselves rather than summarizing them. Pro admits that the mechanisms I proposed can slow down the ratchet. He claims that they’re hypothetical and lack experimental support; I’ll let the reader determine the truth of that. In any event, though, since this isn’t a true ratchet, we only have to slow rate h down rather than stop it if we want rate b to be larger than rate <em>h</em>. The question, then, becomes, how far can we slow it down? I’ve given a variety of options for slowing the ratchet down, and will summarize them below. Genetic recombination. Contrary to Pro’s assertions, it is a valuable asset here, as I have repeatedly explained. Even a linkage block with more negative mutations than beneficial ones can be an asset of sorts—it allows negative mutations to be more efficiently filtered out by natural selection. The randomization inherent in recombination allows the chance for a generation to have fewer harmful traits, and fewer harmful genes, than the previous generation. The ratchet slows. And, in this case, the ratchet can reverse. As I’ve already explained, a good portion of the DNA is actually useless (I don’t know why Pro seems to think I’m referring to mtDNA here). This allows mutations to be truly, absolutely neutral. The ratchet slows. Purifying selection can and will weed out particularly harmful mutations before they become too prominent in the population, at least in populations of significant size. The ratchet slows. The question, then, is whether or not the ratchet has slowed down enough for rate b to be equal to or greater than rate h. Maybe it has and maybe it hasn't, but Pro has given us no reason to think it hasn't, and thus has not fulfille his burden of proof. My thanks to Muted for the debate. It was most stimulating.