science ๐งฌ Your DNA has viral leftovers ๐ค
Roughly eight percent of the human genome is composed of leftover retrovirus elements known as HERVs. These viral sequences integrated into DNA when an ancient retrovirus infected a cell that became part of sperm or egg. The syncytin gene, for example, was repurposed from a viral envelope protein to help form the placenta. This barrier prevents maternal and fetal blood from mixing, avoiding a fatal immune reaction. This shows evolution frequently reuses viral parts for new biological functions.