ERV FAQ: What's all this about the Phoenix Virus? Sounds like a Michael Crichton science fiction story!

This experiment proves that ERVs originated as retroviruses.

https://barryhisblog.blogspot.com/p/whats-all-this-about-phoenix-virus.html

A bunch of mad scientists looked at a set of very similar endogenous retroviruses (ERVs) that lurk in our genomes, and figured that maybe, they all derived from the same retrovirus, a retrovirus that either endogenized (entered the germ-line) independently on separate occasions, or endogenized once and repeatedly integrated in different locations via transposition. Because they thought that each ERV might derive from the same original retrovirus, but was wonky because reverse transcription is so error-prone, they figured that the ERVs were likely to have different incapacitating mutations. All they had to do, they thought, was to look at the genomes of all the ERVs and take a "majority vote" as to what the correct base was at each genetic position, and they might be able to reconstruct the genome of the original retrovirus. 

The reckless fools.

This page explains the experiment in more detail and links to their peer-reviewed report. https://barryhisblog.blogspot.com/p/the-phoenix-virus-explanation-of.html

This not science fiction.

See also, https://journals.asm.org/doi/10.1128/jvi.64.5.2245-2249.1990