He likewise confirmed that if a virus predates humanity, it’s unlikely to be specialized to harm us. “Most viruses are highly specific for their hosts,” Van Etten explains. “That is, humans are resistant to most of the viruses found in the world and resistance is not always due to immunity. For example, if one does not have a receptor for a virus, it will not infect the person.”

And Van Etten reassured that it’s unlikely that will be the case given the age of the viruses: “Probably very unlikely.”

Which is not to say it’s impossible to get a virus from a mummy or frozen sample. “One of the early arguments against getting rid of the last two stocks of smallpox virus [which has been eliminated from the world] was that some person with the disease would be found frozen somewhere,” says Van Etten, “and might infect a human who came in contact with the subject.  To my knowledge this has not happened.”

It could, in theory. Claverie’s primer made one thing clear: permafrost is not ice.