The ancient origins of Hepatitis are coming to light, thanks to virus fragments locked in the genomes of modern songbirds. A "fossilized virus" isn't one embedded in rocks, but rather in the DNA of the host, and this is the first-ever hepatitis-family virus discovered. It was found in the same location in the genomes of five different species of songbird. These birds can be traced to a single ancestor species some 19 million years ago, which pushes back the known age of the virus family by orders of magnitude. The fossilized version is also remarkably similar to current Hepatitis B, implying that it has a slower rate of mutation than previously thought.
Research published in PLos Biology