Ancient virus from the age of the dinosaurs found hidden inside every human

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An ancient virus, dating from the age of the dinosaurs, has been spotted by scientists in an unexpected location.

“It’s kind of hiding in plain sight in the human genome,” says Aris Katzourakis at the University of Oxford.

There are two examples of the long-extinct virus hidden inside every living human.

The fossil viruses are very unlike the ones that infect us with everything from Covid-19 to the common cold.

Modern viruses tend to be retroviruses, which actively insert DNA copies of their RNA genes into the genomes of the cells they infect. Between 5 per cent and 10 per cent of the human genome consists “junk DNA” from retroviruses.

The recently-discovered fossil viruses belong to an ancient group of DNA viruses known by scientists as Mavericks.

Traces of fossil Mavericks have been identified in fish, amphibians and reptiles in the past, but the only previous known example of Maverick DNA inside mammals is in cast, and is thought to have been cross-contaminated from fish.

But these very ancient viral traces have been with us all along.

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In a new paper documenting the discovery, Katzourakis and his co-author Jose Gabriel Nino Barreat, write that one of the Maverick viruses was introduced into the genome of one of our distant ancestors at least 105 million years ago.

“We further estimate the age of the viral ancestor around 268 [million years],” they write.

“Our results provide evidence for some of the oldest viral integrations in the human genome and insights into the ancient interactions of viruses with the ancestors of modern-day mammals”.

“There aren’t that many non-retroviral viruses in our genome,” Katzourakis told New Scientist. “This is the only DNA virus in the human genome that we know of, and it’s certainly the oldest non-retroviral insertion in our genomes.”

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