Ok, I'll admit it. ERVs ARE junk DNA - well, sort of.

https://barryhisblog.blogspot.com/p/ok-ill-admit-it-ervs-are-junk-dna-well.html

Endogenous retroviruses (ERVs) are the inherited remnants of viruses in our genomes. The fact that most of them are in precisely corresponding positions in our DNA and that of chimps and other primates proves that we are all related by common ancestry.
  
If you don't know about ERVs, click on the ERV FAQ link at the top of the page.

People who resist this proof claim that it can't be true because ERVs are not "junk DNA". They perform functions and were therefore designed.

I was a "service brat" when I was a kid. Dad was a Royal Air Force fighter pilot and we lived on R.A.F. bases. It was not so long after WWII. Some of our gangs' favourite places to explore and mess around were warplane scrapyards. Nobody worried too much about the hazardous materials we might come across. There were so many fascinating bits and pieces, many of which we didn't understand the original purpose of, which made them even more intriguing to us. We were soon playing fantasy games with them and making up imaginary functions, but we were soon re-purposing them to make weapons, shields, handcarts etc.

Later, we would be messing with scrapped circuit boards and electronic valves and other components. One of our number had a gift. He had no training for it, but he figured out how, I never understood how, to build working radio transmitters and guitar amplifiers from scrap. He once connected a cobbled-together transmitter to the metal fence surrounding the base to make a huge aerial. The effect on the military, when he turned the transmitter on, was like kicking the proverbial hornet's nest! Boy, were we in trouble!

The people who try to deny the reality of evolutionary science point to function in ERV components, and claim that "evolutionists" (ordinary people who accept evolution) take the position that all ERV genetic components are junk. No. "Evolutionists" do not claim that it is all junk, and the proof of common ancestry does not depend on it all being junk. Still, a dishonest straw-man is all that these deniers have to convince themselves and their trembling faithful subscribers that they have a point. They do not.

Now let's be very clear about what we mean here. "Junk" can mean stuff that has no purpose and never had any purpose, and it can mean stuff that did have a purpose but no longer serves that purpose. I prefer to call the latter "scrap". Scrap may be useless but potentially useful reusable material, or, as in the case of our weapons, karts, amplifiers and transmitters, material that has been re-purposed. This is what we have in some of the bits and bobs in our ERVs.

There are no fully functional ERVs in our genomes, continually generating new retroviruses. Life would not be - er - viable. What there is, in our DNA, are examples of scrapped retroviral genetic material, some of which has been re-purposed by evolution. How can evolution re-purpose viral genetic material? Well, the replication cycle of a retrovirus is rather error prone. Mutations to its genetics can occur immediately on insertion into our DNA. Most of these errors, when they do occur, will disable the virus and leave us unaffected. Some will cause even more damage. But some will, just by luck, confer a reproductive advantage. It is these that will spread and increase in the species population generation by generation. The good old natural selection of heritable variations. Only this is genetics not being built from scratch, but a far more likely process - the tinkering with "junk" that once did have a different purpose. The scientific name for it is "exaptation" - the adaptation of originally "exo" genetic material, or, the re-purposing of scrap!

A commentator says, "The creationist claim that ERVs are 'created' and were always part of genomes is like coming across a rusty old Ford in the desert, the engine of which is being used as a generator, complete with wheels, steering wheel, doors, clutch and breaks, then claiming 'it was designed as a generator and it was never a car'

And clearly, this was designed as a flower bed.

See also https://barryhisblog.blogspot.com/p/in-science-we-apply-principle-of.html, a bunch of questions the design hypothesis raises, that nobody has been able to answer.

https://barryhisblog.blogspot.com/p/ok-ill-admit-it-ervs-are-junk-dna-well.html