In a recent blog, I talked about possible methods of falsifying the Theory of Evolution. A reader (NP) made the following comment:“…finding any lineage of organisms that does not use DNA or RNA as its hereditary material would falsify common descent. But of course, given that every organism we know of uses DNA, it sounds a bit ridiculous.”Now, my apologies to NP because I didn’t take that as a serious test and I misunderstood NP to be saying in advance that he knew it was a ridiculous test. Afterall, he did say "it sounds a bit ridiculous." But NP left another comment saying the following:
"RK, I already pointed out one. Find any organism that does not use DNA/RNA as it's hereditary material. That would falsify the notion that all life on earth has common ancestry."So it seems NP does mean that as a serious test of evolution. But that can’t be a true test because evolution does not require every creature to have DNA/RNA and I’ll show you why. Evolutionists assume there was a supposed common ancestor of all living things. This creature would have been the first reproducing life form on earth and would have had something like RNA. However, there is nothing about evolution that excludes some other life form arising which does not use RNA/DNA to reproduce. So if we found some life form that did not have DNA, it doesn’t falsify evolution in the slightest. It is only evidence that the new life form is not descended from or related to all previously known life forms.
But I want to talk a little more about DNA. The title of this thread is not aimed at NP in particular. Rather, all evolutionists have co-opted DNA and now use it as evidence for their theory. NP’s comments are not originally his (no offense, NP) but I will take the opportunity of his comments to address the evolutionist spin on DNA.
NP said:
"compare the genome of a chimpanzee to that of a human and a chicken. If the chimp and chicken have more homologous sequences than the chimp and human, that would falsify common ancestry between humans and chimps."That sounds reasonable, doesn’t it? Here’s why similar DNA doesn’t really validate evolution: DNA is often compared to blueprints that provide instructions for the constructing of cells. If two organisms are similar, then doesn’t it only make sense that the instructions that build the organisms would be similar? A human is most like a chimp, less like a bear, and least like a bird. Therefore, a human’s DNA should be most like a chimp’s, less like a bear’s, and least like a bird’s. Of course, that’s exactly what we see in nature. If similar creatures did not have similar DNA, then I would say we know nothing about DNA.
Now, the other angle evolutionists take is the similarity in non-coding DNA. Some people estimate that only about 8% of the human genome is coding DNA. The rest has been called “junk” DNA. So if the non-coding DNA were similar, they say that is evidence of common ancestry. The problem with this hypothesis is the assumption that non-coding DNA is truly non-coding. For the last several years, we’ve continuously discovered function in the non-coding parts of DNA. So if the non-coding part of DNA is truly coding then I direct you again to my first point – similar creatures should have similar DNA.
Finally, DNA should be the silver bullet that kills evolution. Because of DNA, bears only reproduce bears and birds only reproduce birds. The remarkable ability of DNA to repair itself or to mask mutations from being expressed make creatures resistant to change. Yet it is that tiny mutation expressed for thousands of generations that is the hope of evolution. Time and mutation are the heroes of the story; without them, evolution is a fairy tale about a frog turning into a prince – over a million years.
DNA is a broad subject and a lot more could be said about it. In short though, DNA is not the champion of evolution. It’s not even close.
As I pointed out in a previous comment, evolution is a broad theory that explains several different observations. Thus, it makes it highly improbable that any single observation could falsify the entire theory. Instead, there are several tests that could falsify various aspects of the theory.
ReplyDeleteI see your point about the precursor to life as we know it utilizing a hereditary material other than RNA or DNA. However, it would probably be a related molecule, since it would be highly unlikely that a prototypic organism could switch from a completely different kind of molecule to RNA/DNA. Nonetheless, seeing as virtually every organism that we know of uses RNA/DNA, this is a moot point.
That sounds reasonable, doesn’t it? Here’s why similar DNA doesn’t really validate evolution: DNA is often compared to blueprints that provide instructions for the constructing of cells. If two organisms are similar, then doesn’t it only make sense that the instructions that build the organisms would be similar? A human is most like a chimp, less like a bear, and least like a bird. Therefore, a human’s DNA should be most like a chimp’s, less like a bear’s, and least like a bird’s. Of course, that’s exactly what we see in nature. If similar creatures did not have similar DNA, then I would say we know nothing about DNA.
This is a common rationalization used by creationists, but it simply doesn't hold any water. Many proteins are highly conserved in most organisms in terms of their function, and so there's no reason why the Aplysia RhoA protein should be any different from the mouse RhoA or the human RhoA. If one were to take mouse RhoA and express it in African clawed frogs, the protein would still be functional. So there's no real reason for a putative magic designer to make mouse RhoA resemble Rat RhoA more closely than mouse RhoA resembles human RhoA. Likewise, there's no reason why mouse RhoA should be closer to human RhoA than to frog RhoA. In fact, many differences that exist in the sequences of certain genes are neutral, i.e. they do not alter the function. Therefore, there's no reason why there should be fewer neutral substitutions between a human and chimpanzee gene than between a human and a frog.
Furthermore, your argument simply breaks down when you consider the phenomenon of convergent evolution. According to your line of reasoning, a Tasmanian wolf and a gray wolf should have more similarities in conserved genes than a gray wolf and a rabbit. But this is not the case. Also consider the fossa, a fascinating animal that at first glance looks similar to a leopard. Owing to its "design", you might then posit that a fossa has more similar DNA compared to a leopard than a mongoose. You would be wrong. Dissimilar DNA can create convergent phenotypes.
Now, the other angle evolutionists take is the similarity in non-coding DNA. Some people estimate that only about 3% of the human genome is coding DNA. The rest has been called “junk” DNA. So if the non-coding DNA were similar, they say that is evidence of common ancestry. The problem with this hypothesis is the assumption that non-coding DNA is truly non-coding. For the last several years, we’ve continuously discovered function in the non-coding parts of DNA. So if the non-coding part of DNA is truly coding then I direct you again to my first point – similar creatures should have similar DNA.
Well, you are now fallaciously assuming that just because some so-called junk DNA does have a function, that all of it does.
Our genome has ancestral retroviral DNA that has become mutated over time. It would seem rather bizarre for a designer to make it look like our ancestors got infected with retroviruses that became fixed in the germline, don't you think? For the most part it is junk; in some cases, where the retroviral insertion was inserted into the regulatory region of a gene it may have had a selectable effect. But then again, just because it has a function does not imply it is a product of design, especially when a retroviral sequence is not necessary when any other sequence would do.
Finally, DNA should be the silver bullet that kills evolution. Because of DNA, bears only reproduce bears and birds only reproduce birds. The remarkable ability of DNA to repair itself or to mask mutations from being expressed make creatures resistant to change. Yet it is that tiny mutation expressed for thousands of generations that is the hope of evolution. Time and mutation are the heroes of the story; without them, evolution is a fairy tale about a frog turning into a prince – over a million years.
Despite the presence of DNA repair mechanisms, mutations still occur. It's a fact. Furthermore, variation occurs through recombination as well. Therefore, it is inaccurate to say that organisms are resistant to change, and the fossil record clearly tells a very different story (cue denial of fossil evidence, or examples of stasis). Saying that a bird always gives rise to a bird is trivial considering the huge diversity of bird species. Furthermore, I could just as well say that dinosaurs give rise to dinosaurs, and that would still encapsulate a huge amount of evolutionary change. After all, dinosaurs still exist. ;)
Look, RK: you seem like a smart guy, but most of your objections to evolution are rather superficial. I would invite you to actually look closer at the evidence. The problem is you keep thinking it's some sort of exercise in God-denial, so you end up practising your own brand of denialism. Evolution is a fascinating process, and the wealth of evidence from several independent lines of inquiry supports it. Science is interesting and should be appreciated.
NP, you said, "Well, you are now fallaciously assuming that just because some so-called junk DNA does have a function, that all of it does."
ReplyDeleteIt looks as if the ENCODE project has turned this "fallacious assumption" into fact now that we know that at least 80% of what has been referred to as "junk DNA" actually has specific function, while the remaining 20% may as well with further study. Of course, this embarrassing new evidence will be reinterpreted back into the theory as Dawkins has already done.