Tracing the ancient origin of retroviruses - the family of viruses that includes HIV - is a big undertaking, partly because of the absence of fossils. But a new study conducted by researchers at Oxford University suggests that retroviruses are nearly half a billion years old, significantly older than previously thought.
Until now, scientists thought that retroviruses traced back roughly 100 million years, about as old as terrestrial placental mammals. But at half a billion years old, retroviruses probably developed in marine vertebrates.
According to the study, retroviruses made the transition from the sea to land along with the evolution of terrestrial vertebrates. "Their widespread distribution is a result of ancient origins, not simply the tendency of retroviruses to cross species boundaries," Aris Katzourakis, associate professor at Oxford University's Department of Zoology and author of the study, told Seeker.
"We tend to think of retroviruses over recent timescales, for example, HIV-1 crossed from chimpanzees to humans about 100 years ago, leading to the AIDS pandemic," Katzourakis said. "Our work provides a context in which to understand the association of retroviruses with their hosts," he said.