Retroviruses, a Family That Includes HIV, Evolved During the Early Paleozoic Era

Researchers from Oxford University have discovered that retroviruses have existed since the early Paleozoic Era, half a billion years ago. Scientists believed that they had evolved more recently and the team’s findings are providing new insights into the evolution of viruses, including HIV. The details are in a paper that was just published in the journal Nature Communications.

Retroviridae is an odd family of viruses that includes a cancer-causing virus called the human T cell leukemia virus as well as the human immunodeficiency virus (HIV). Retroviruses incorporate their genetic material into the host cell they’ve infected, just like any other virus. However, they do it backwards. Other viruses convert DNA into RNA but retroviruses convert RNA back into DNA. This strange method is the defining feature of a retrovirus. They evolved a long time ago but little was known about their exact origin.

A team of scientists studied the closest relatives of retroviruses, the so-called “foamy” viruses. These viruses, which are common in mammals, contain bits of genetic material from retroviruses. These sequences of viral DNA were used in combination with modern phylogenetic techniques to study the evolution of the Retroviridae family.

The team was surprised to learn that retroviruses date back to at least 450 million years ago, during the early Paleozoic Era. This shows that they must have originated in the ocean when vertebrates were first evolving. Scientists believed they had evolved much more recently, making the findings especially important.

Retroviruses evolved about half a billion years ago, which makes Retroviridae one of the oldest viral families that still exists. They originated in a marine setting, before modern vertebrates had evolved. This new information will provide researchers with a fuller picture of how retroviruses evolved and changed over time. By fully understanding this strange group of viruses, scientists may be better equipped to study HIV and other retroviruses that are dangerous to humans.


Aiewsakun P, Katzourakis A. Marine origin of retroviruses in the early Palaeozoic Era. Nature Communications (2017).

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