Creationists cant deal with ERVs. They have no answer to the problems ERVs pose to Creationism. They have no alternative explanation for the weight ERVs lend to evilution.
However, this doesnt stop Creationists from bluffing/lying to save face in front of the True Believers.
One of the more baffling responses Ive gotten to ERVs is ‘ERVs dont exist. They arent really ancient retroviral fossils.’ The most common response is ‘ERVs arent junk DNA! See, this one gene (out of 1,000,000 similar genes that are clearly junk) has been co-opted for use by the host! So, YAY JESUS!’
Real world, real time evidence against these two claims is currently trying to eliminate koalas as a species: Koala Retrovirus
Lets start at the beginning. A long time ago, zoologists/animal technicians/etc, noticed that their koalas werent dying from old age or falling out of trees or whatever– Koalas were dying from leukemias, others were getting lymphomas, and others were dying from complications of immunodeficiencies (a big one in koalas is chlamydia).
Now, there could be any number of reasons for this. Koalas were hunted to near extinction– this could be the result of non-optimal genetic diversity and inbreeding. Maybe its a transmissable cancer, like what happened to Tasmanian Devils as a result of their decrease in genetic diversity. Maybe eucalyptus trees are preferentially sucking up some carcinogen from the environment, and koalas are getting mega-doses of something awful from their diet. Since chlamydia is such a big deal in koalas, maybe their leukemias/lymphomas are the result of a different kind of koala-STD, like a koala-EBV or something.
Or maybe a retrovirus is causing all the trouble. Retroviruses cause leukemias and lymphomas and immunodeficiencies. Why not look?
The virus they found, KoRV, is kinda related to Gibbon Ape Leukemia Virus. Gibbons live in Asia. Koalas live in Australia. How the hell did Koalas get infected with a Gibbon retrovirus?
There are a few answers for this.
1– KoRV isnt GaLV. We dont know if Koalas literally got this virus from literal Gibbons, that is, GaLV is the direct parent of KoRV (like SIV-cpz is the direct parent of HIV-1). They could have both been infected from a similar common ancestor, thus still appear related, but have both gone on their own respective evolutionary trajectories (like chimpanzees and humans share a common ancestor. chimpanzees didnt directly evolve into humans).
2– There could have been an intermediary. Koalas didnt need to be hunting Gibbons to get a retrovirus from them. GaLV and KoRV are gammaretroviruses, related to Murine Leukemia Virus*. Rats can be infected with any of these, so they could have carried them from Asia to Australia, no prob.
3– An ancestor of ‘koalas’ could have been infected from an ancestor of ‘gibbons’ a bazillion years ago, when both ancestors shared a common environment. I mean, humans and chimpanzees and other old-world apes all share ERVs. Just because koalas and gibbons are environmentally separated now doesnt mean they always were.
Heres the problem with #3: There was a colony of koalas isolated from everyone else in the 1920s. They are fine. No KoRV. No evidence of KoRV.
And the KoRV they are finding in the koalas that are infected?
Its endogenous, at different locations in different koalas (sometimes they share a locus, sometimes there are novel ones).
Its endogenous, and its still very, very active. So active, its killing the koalas. An ERV that is not junk is killing koalas.
And the ‘youngest’ ERV weve ever found? HERV-Ks are the youngest ones weve got– millions of years old. Millions. I think pigs have a PERV that is ‘only’ 3.5 million years old. And now we are watching an endogenization event happen in koalas.
Or an extinction event.
* Isnt it weird how _LV retroviruses cause leukemias and lymphomas in their respective species, except for humans? And how people studying _LVs in other organisms have no drama and no difficulty using standard reagents, but people studying XMRV/human-MLV/magic-eye-MLV have all this trouble? Isnt that weird? I think thats weird. lol.