Scientists have discovered when the first ancestors of HIV appeared on Earth

First retroviruses, including the "ancestors" of human immunodeficiency virus (HIV), appeared on Earth about 500 million years ago, about 200-300 million years earlier than previously believed by experts, say scientists in a research published in the journal Nature. Retroviruses are a special type of virus that can penetrate into living cells, to restore their DNA using RNA templates and insert its genetic code into the genome of the victim. Retroviruses, which include HIV, affect mainly vertebrates, and traces of their existence can be found in the DNA of humans and all other animals in the form of so-called transposons - mobile DNA segments that are capable of self-replication and movement within the genome. Such retroviruses age suggests that they arose prior to the development of so-called adaptive immunity - a distinctive feature of all vertebrates, allowing mammals, birds, frogs and fish to survive when new, previously unknown viruses and microbes appear. As the authors say, the emergence of retroviruses and possible struggle of our ancestors with the "precursors of HIV" could have caused the birth of this part of the immune system.