Retroviruses ’almost half a billion years old’

Researchers have found that retroviruses could be half a billion years old - several hundred million years older than previously thought. Retroviruses - the family of viruses that includes HIV - are almost half a billion years old, according to new research by scientists at Oxford University. That's several hundred million years older than previously thought and suggests retroviruses have ancient marine origins, having been with their animal hosts through the evolutionary transition from sea to land. The findings, reported , will help us understand more about the continuing 'arms race' between viruses and their hosts. Study author Dr Aris Katzourakis, from Oxford University's Department of Zoology, said: 'Very little has been known about the ancient origin of retroviruses, partly because of the absence of geological fossil records. Retroviruses are broadly distributed among vertebrates and can also transmit between hosts, leading to novel diseases such as HIV, and they have been shown to be capable of leaping between distantly related hosts such as birds and mammals. But until now, it was thought that retroviruses were relative newcomers - possibly as recent as 100 million years in age.