Retroviruses are more retro than we thought

Scientists have found that some viruses' ancestry is over four times older than previously thought, dating to a time long before the dinosaurs.

Retroviruses—the class of virus that includes HIV—were previously thought to have evolved around 100 million years ago.

But researchers Pakorn Aiewsakun and Aris Katzourakis have traced their likely origin to the early Paleozoic Era, over 450 million years ago.

Ordinary viruses hijack cells with their own DNA molecules to produce RNA, which the viruses use to reproduce. But some viruses work in reverse: they use RNA to make DNA, hence the term "retrovirus."

And now, it seems that they're "retro" in more ways than one.

Aiewsakun and Katzourakis believe that retroviruses evolved alongside the first bony fish, some of the earliest vertebrate creatures to inhabit the Earth.

"(The family of) retroviruses as a whole have an ancient marine origin and originated together with, if not before, their jawed vertebrate hosts," the abstract of their paper, published in the journal Nature, said.

The scientists were able to make this assessment by looking closely at a special kind of retrovirus that has left behind minute genetic traces in generations of animals.

By comparing the patterns left by these so-called endogenous retroviruses (ERVs) between different species, the scientists are able to hazard a guess as to how long ago and how far back in the evolutionary tree animals were infected. — GMA News