Viruses are the most diverse and abundant type of biological entity on Earth, infecting species from all of life’s domains and being found in almost all types of environments. They are gaining increasing attention from scientists, officials and the public due to recent major outbreaks with human health consequences (e.g., AIDS, SARS, COVID-19) and a growing appreciation of the impact viruses have had on the long-term development of both the biosphere and geosphere. The ability to identify viruses in ancient times is of importance in promoting our understanding of viral evolution and the relationships of viruses to their hosts and to paleoclimate conditions, enabling predictions of present and future impacts of the virosphere on life and the climate system.

The study of ancient viruses and the evolutionary history of viruses using genomics has been termed “paleovirology” [1]. It is based largely on analysis of endogenous viral elements (EVEs), which represent the viral components of a host’s genome. Paleovirology is now a burgeoning field thanks to the development of advanced metagenomic next-generation sequencing techniques [2]. Its successes include detection of genomic viral signatures in host cells from sediments that are thousands of years old. However, this field has made very limited use of the fossil record of viruses in rocks.