One conserved over the whole tree of life? That's like imagining an editing bug that Emacs and Vim have both carefully and inexplicably preserved from the last universal common text editor.

The genome is full of retrovirus remnants, so there’s a way for a parasite to piggyback on the host genome. Alu repeats in human genome are one such example. But there’s a hypothesis that these get “domesticated” by the genome and start serving a function.