RESIDUAL DNA. “So what’s the other 90 percent of the human genome up to? It has been called junk, and although scientists don’t much like that term, junk is what a lot of it appears to be. Some of that DNA, for instance, is leftover fragments of dead viruses that invaded our ancestors’ genomes aeons ago.”
https://www.geneticliteracyproject.org/2014/08/05/how-much-of-human-dna-is-doing-something/