Endogenous Retroviruses

Approximately 8% of the human genome consists of ancient viral DNA - remnants of infections our ancestors survived millions of years ago. Some of these 'fossil viruses' have been domesticated: syncytin genes (from retroviruses) are essential for placenta formation in mammals. Without ancient viral infection, placental pregnancy wouldn't exist.

ERVs demonstrate parasitism-to-mutualism evolution. What began as harmful infection became, over millions of years, essential biology. The genetic 'scars' of past conflict now enable new capabilities. The business parallel is hostile acquisitions that eventually integrate: competitors absorbed unwillingly who over time become essential divisions, or regulations opposed by industry that eventually become competitive advantages.