ID/creationists claim that ERV’s match because independent insertions will produce the same insertions at the same base in each of the genomes. I’ve been trying to see if this claim is valid. The argument against this that I’ve read is about PTERV1 insertions and goes something like this:
Gorillas branched off of the chimp/human lineage first followed by the chimp and human lineages splitting. Therefore, if the PtERV insertions happened before the gorilla lineage split off then they should be found in the genomes of all three species. They aren’t. Instead, PtERV1 insertions are found in the chimp and gorilla genomes. This means those insertions had to occur after all three lineages were on their own. Common ancestry would predict that these insertions happened independently in the chimp and gorilla genome which would also mean that they should NOT be found at the same location in the chimp and gorilla genomes due to the random insertion of retroviruses into the host genome.
ID/creationism prediction: PtERV1 insertions should be found at the same location.
Common ancestry prediction: PtERV1 insertions should NOT be found at the same location.
What do we observe? All or nearly all of the PtERV1 insertions are not found at the same location in the chimp and gorilla genomes, exactly what common ancestry predicts and opposite of what ID/creationism predicts.
My query is that on the common decent hypothesis if the PtERV 1 insertions had been at the same location in chimps and gorillas then it wouldn’t falsify common decent, instead we’d just say that humans branched off of the chimp/gorilla lineage first followed by the gorilla and chimp lineages splitting. It seem the only reason for saying “gorillas branched off of the chimp/human lineage first followed by the chimp and human lineages splitting” is the evidence from PTERV1 insertions. Which seems to be a circular argument. But maybe I’m missing something.
Having said that, even if this is a circular argument, doesn’t it at least show that the ID/Creationist prediction doesn’t work as they believe the insertions are site specific down to the base pair, as the PTERV1 show this isn’t true. So even if PTERV1 insertions couldn’t be used to support/falsify common decent, they can be used to falsify the ID/Creationist claim that insertions are site specific.
Indeed you are. The evidence for the branching order of the three African apes (Homo, Pan, Gorilla) comes from the entire genome, so there is no circular argument. It’s to this background that we need to fit any explanation of PTERV1 insertions. If these insertions were uniformly consistent with the gorilla-chimp tree rather than the chimp-human tree, that would be very difficult to explain under any reasonable evolutionary scenario.
An insertion could occur in the common ancestor of chimps, gorilla, and human. It is not in the whole population, but in one genome, in one of the two copies of the chromosome at that point. Coalescent effects (“independent lineage sorting”) can result in the copies ending up in chimps and gorilla but not in human. With variations of bases at sites in the genome, that happens about 15% of the time, and similarly for human and gorilla. For human and the chimps, about 70% of the time. So this is not at all impossible in one case. Looking at many of them would show the general pattern.
Yes, ILS can explain anomalous patterns for around 15% of insertions. But the claim here was for all of them. Loss in the human lineage could explain a few more, but that would require perfect excision that preserved the flanking sequences, even more unlikely.
(It’s worth remembering that these are attempted explanations of a pattern that does not in fact occur.)
Multiple websites including evolutionnews.org. I think it’s pretty much the only reply a ID/YEC could make. We are obviously talking here about insertions, so if there not site specific how else can we explain why almost all ERV’s in humans are found at the same position in chimps and other primates?
May I just clarify that one last time. The fact that PTERV1 insertions are present in both aren’t gorilla and chimps, but not at the same location shows that they are NOT site specific.
Yeah, they can be “ingenious in their stupidity”. Funny when they think that if the ERV, or pseudogene etc, can be shown to have some function that that somehow that means it’s no longer evidence for common decent, whereas it may well have just taken on a new function
Out of tens of thousands of ERV elements in the human genome, roughly how many are known to occupy the same sites in humans and chimpanzees? According to this Talk-Origins article, at least seven.
I thought this argument you initially cited was a very bad one but I did not know that. Unless someone wants to explain what I’m misunderstanding.
Anyway, ERVs are not an airtight case for common ancestry.
This article seems confused on many points, but it never quite comes out and claims what you say. It may be implied but it’s never actually stated. Whether that’s clever plausible deniability and obfuscation or just poor writing and poor comprehension of sources is not clear.
