Originally posted by s0uljah
Hey Jerry-
I respect your views and as I said before, you know a lot about science/math, etc. 
But, I honestly don't think that this makes sense at all. Why would the gene get passed around for several generations if it never offered a benefit? I'm just talking from the natural selection perspective...
s0uljah:
Evolution works on populations, not individuals. If the gene is a mutation, it is probably not expressed in the first individual who bears it, and therefore it can have little potential for actually PREVENTING that organism from passing it to the next generation. If Beetle A has 10 offspring, 5 of them are likely to carry the gene, and not likely to express it. If four of the next generation (one of them gets picked off by a bird or some such) have an average of ten offspring each, then the gene exists in forty individuals, and still, few are likely to express it. After the next generation, there may be 160 who carry the gene, and perhaps five who express it. Another generation along, perhaps fifty or more express the gene. Now some of the local birds have probably eaten one or two of the bad-tasting bugs and have begun to see this colony of beetles as the second-choice for a meal. Natural selection has begun. The beetles in the population where this trait is present are beginning to be looked over by the birds, in favor of some of their neighbors.
Eventually, as happens in nature, the beetles from the original population establish new populations in the surrounding areas. Some from the original population take the mutant gene to their new colony, some do not. Eventually, the birds will learn which colonies are tasty and which aren't. The tasty ones will diminish in the region and the populations with few or no members carrying the mutation will steadily diminish, as the individuals are scarfed up by a bird before they reproduce more and more often. At the same time, the populations that have more individuals with the gene are increasingly overlooked by the birds and continue to flourish.
The populations that lack the gene entirely are the first to become locally extinct. Meanwhile, the populations that have more individuals with the gene are the most likely to form new populations, and those populations will also have fewer or more individuals with the genes.
Eventually, the time comes that over the local range of the beetle, there is 100% expression of the mutant gene. Elsewhere in the world (with different predators who have never encountered the bad-tasting gene) other beetles of the same original species carry on and evolve other defenses against their own predators. Since these other beetles and our mutant beetles do not share a local range, they never mix genes. Over time, they diverge genetically and morphologically from each other so that if the two should ever meet, there is a strong chance that they would not "recognize" each other for mating purposes, or would attempt to mate but fail due to genetic incompatibility. Bingo: we started with one species of Beetles without the quinone, and ended with one species that has the quinone and one species that does not... and the remarkable thing is that this "micro" change can take place over the course of a few thousand generations of beetles - which is only a few tens of lives of the birds around them, and perhaps a few lifetimes of humans. When the birds become desperate enough to eat the quinone beetles, or when another predator that doesn't mind the taste comes along, there is more pressure on the new beetle species and the cycle starts over, modifying their present body plans and body chemistry to create defenses against the new threats. The Bombadier Beetle could evolve in this way over a geologically very brief period of time.
You can probably infer from this description how a deleterious mutation is removed from a population by natural selection as well.
