Also interesting are HERVs - human endogenous retroviruses which integrated into the human or our ancestor species’ genomes. They have degraded over time so none of the human hervs seem to be capable of activating but there are some in other mammals that can fully reactivate.
In humans even though hervs don’t reactivate into infectious viruses they have been implicated in both harmful (senescence during aging[0]) and beneficial (protection from modern retroviruses)[1] activities in the body.
In humans even though hervs don’t reactivate into infectious viruses they have been implicated in both harmful (senescence during aging[0]) and beneficial (protection from modern retroviruses)[1] activities in the body.
They might be up to 8% of the human genome.
0: https://www.cell.com/cell/pdf/S0092-8674(22)01530-6.pdf
1:https://www.microbe.tv/twiv/twiv-956/