These analogies aren’t helping. You’re using analogies whereby the functional components (rivets, hooks/loops) are being implied to be uniformly functional in the structures in which they exist.
DNA doesn’t work like that. Small changes to DNA could have no effect, moderate effects, or severe effects. It all depends on what is being changed with respect to specific DNA sequences and the role they play in phenotypic development.
This highlights the problem with trying to use analogies are arguments. The implication is that the analogy works the same as the thing the analogy is being compared to. But DNA doesn’t function like velcro or rivets.
Howe C.J., Barbrook A.C., Spencer M., Robinson P., Bordalejo B., Mooney L.R. Manuscript evolution. Trends in Genetics 2001; 17:147-152.
Abstract
Frequently, letters, words and sentences are used in undergraduate textbooks and the popular press as an analogy for the coding, transfer and corruption of information in DNA. We discuss here how the converse can be exploited, by using programs designed for biological analysis of sequence evolution to uncover the relationships between different manuscript versions of a text. We point out similarities between the evolution of DNA and the evolution of texts.
Fortunately (!?) for Young Earth Creationist organizations, such analogies are very convincing to their donors and fans, most of whom are totally clueless as to even the definition of evolution, let alone the basics of how evolutionary processes work and the piles and piles of evidence associated with them.
If someone is a glutton for punishment and prone to Gaper’s Block—as I confess I am—I recommend this time-wasting article from Answers in Genesis:
Yes, it is focused on “six 24-hour days” rather than evolution per se but the mentality is fascinating. (It is basically making the argument, "I know that I’m right and everybody else is wrong—including other Christians—because the Creator told me so and he was there at creation. So there! I gotcha!)
Do you know why godly creation scientists believe God created the world in six 24-hour days?
They are brilliant.
They have PhDs.
They understand the plain meaning of Genesis 1 and 2.
While all three of those options may be true, the real reason they know the earth is young is that the Holy Spirit taught them the truth.
The main problem with @Giltil’s analogy, it seems to me, is that it assumes one cannot determine whether or not a rivet serves a function. In order for his analogy to work, even an expert engineer would be unable to differentiate between a pile of random rivets, completely unlike those used elsewhere in the structure, carelessly dropped on the ground by a visitor, and rivets that hold a crucial girder in place.
@Giltil would likely argue that there was no way to be sure that the rivet pile wasn’t performing an important function that was too subtle for us to understand.
The retroviral ones are bounded by long terminal repeats (LTRs), which are excised very often (10^-5). So we can see whether this makes any difference.
I worked on one of them as a postdoc. It is in an intron of the Myo5a gene and caused a tissue-specific phenotype. It reverted to wild-type, leaving a single LTR behind.
Much of what we know about human cancer comes from studying those turning on adjacent oncogenes in mice and chickens.
Analogies are not useful for establishing whether ERVs are functional. At best they might help you clarify some point you wish to make, but they do not demonstrate anything about the genome. It takes biochemical and bioinformatics research to determine this, it can’t be demonstrated with an analogy (whether to buildings or anything else).
Incidentally the verdict is in: ERVs are mostly evolutionary remnants. Junk DNA. There’s some functional exceptions here or there, but they’re comparatively much more rare than the majority that are nonfunctional.
Worse still for creationism, what fraction of them or whether they are functional or not is irrelevant to their being perfectly good evidence for common descent, which they are since they support the standard primate phylogeny.
My analogies (rivets, Velcro) are not designed to demonstrate that Alu elements are functional, not at all. Their purpose instead is to show that you cannot dismiss their functionality on the sole basis that when you remove one element no clear effect on the phenotype is observed. And for that purpose, they are doing well.
But who has even claimed such a thing? Who is it you purport to rebut with this analogy? The evidence for junk is a conjunction of multiple independent lines of evidence. It’s not just made on the basis of a single putative knock-out experiment.
The limitation of analogies is that nothing is so like a thing as the thing itself, meaning, while analogies can be helpful for instruction, ultimately all that matters is the biochemistry.
You are deflecting from the point that for much of junk DNA, such as generally ERV’s and pseudogenes, the original function is identified, so functionality is not dismissed but observed to be inoperable.