Exogenous retroviruses represent a fascinating class of viruses that have integrated into the genome of their host organisms. These viruses, characterized by their unique ability to reverse transcribe their RNA genome into DNA, have left an indelible mark on the evolution of various species. One notable example is the human immunodeficiency virus (HIV), responsible for acquired immunodeficiency syndrome (AIDS). HIV, having zoonotic origins, likely jumped from non-human primates to humans in Central Africa. The virus's integration into the human genome has raised intriguing questions about the impact of exogenous retroviruses on human evolution and susceptibility to certain diseases. Research into these viruses extends beyond human health, encompassing diverse organisms, from plants to animals, where exogenous retroviruses have influenced genetic diversity and adaptation over millions of years.