Paleovirology is the study of viruses that existed in the past but are now extinct. In general, viruses cannot leave behind physical fossils,
therefore indirect evidence is used to reconstruct the past. For example, viruses can cause evolution of their hosts, and the signatures of that evolution can be found and interpreted in the present day.
Also, some viral genetic fragments which were integrated into
germline cells of an ancient organism have been passed down to our time as viral fossils,
[ or endogenous viral elements (EVEs). EVEs that originate from the integration of retroviruses are known as endogenous retroviruses, or ERVs, and most viral fossils are ERVs. They may preserve genetic code from millions of years ago, hence the "fossil" terminology, although no one has detected a virus in mineral ]fossil
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...
s.DNA
Deoxyribonucleic acid (; DNA) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix. The polymer carries genetic instructions for the development, functioning, growth and reproduction of al ...
and RNA virus
An RNA virus is a virus characterized by a ribonucleic acid (RNA) based genome. The genome can be single-stranded RNA (ssRNA) or double-stranded (Double-stranded RNA, dsRNA). Notable human diseases caused by RNA viruses include influenza, SARS, ...
es.
Terminology
Although there is no formal classification system for EVEs, they are categorised according to the taxonomy of their viral origin. Indeed, all known viral genome types and replication strategies, as defined by the Baltimore classification, have been found in the genomic fossil record. Acronyms have been designated to describe different types of viral fossil.
*EVE: Endogenous viral element
*ERV: Endogenous retrovirus
Endogenous retroviruses (ERVs) are endogenous viral elements in the genome that closely resemble and can be derived from retroviruses. They are abundant in the genomes of jawed vertebrates, and they comprise up to 5–8% of the human genome ( ...
*HERV: Human Endogenous Retrovirus
*NIRV: Viral fossils originating from non-retroviral RNA viruses have been termed Non-retroviral Integrated RNA Viruses or NIRVs. Unlike other types of viral fossils, NIRV formation requires borrowing the integration machinery that is coded by the host genome or by a co-infecting retrovirus.
Other viral fossils originate from DNA viruses such as hepadnaviruses (a group that includes hepatitis B).["Ancient "Fossil" Virus Shows Infection to Be Millions of Years Old"]
by Katherine Harmon, ''Scientific American
''Scientific American'', informally abbreviated ''SciAm'' or sometimes ''SA'', is an American popular science magazine. Many scientists, including Albert Einstein and Nikola Tesla, have contributed articles to it, with more than 150 Nobel Pri ...
,'' September 29, 2010
Resurrection
Successful attempts to "resurrect" extinct viruses from the DNA fossils have been reported."How to Resurrect an Extinct Retrovirus"
''Scientific American
''Scientific American'', informally abbreviated ''SciAm'' or sometimes ''SA'', is an American popular science magazine. Many scientists, including Albert Einstein and Nikola Tesla, have contributed articles to it, with more than 150 Nobel Pri ...
,'' November 2, 2006 In addition,
''Pithovirus sibericum'' was revived from a 30,000-year-old
ice core harvested from
permafrost
Permafrost () is soil or underwater sediment which continuously remains below for two years or more; the oldest permafrost has been continuously frozen for around 700,000 years. Whilst the shallowest permafrost has a vertical extent of below ...
in
Siberia
Siberia ( ; , ) is an extensive geographical region comprising all of North Asia, from the Ural Mountains in the west to the Pacific Ocean in the east. It has formed a part of the sovereign territory of Russia and its predecessor states ...
, Russia.
See also
*
Ancient DNA
*
Endogenous retrovirus
Endogenous retroviruses (ERVs) are endogenous viral elements in the genome that closely resemble and can be derived from retroviruses. They are abundant in the genomes of jawed vertebrates, and they comprise up to 5–8% of the human genome ( ...
*
Human Genome Project
*
Insertional mutagenesis
* ''
Invertebrate iridescent virus 31''
*
Micropaleontology
*
Paleobiology
Paleobiology (or palaeobiology) is an interdisciplinary field that combines the methods and findings found in both the earth sciences and the life sciences. An investigator in this field is known as a paleobiologist.
Paleobiology is closely ...
*
Paleogenetics
*
Viral eukaryogenesis
References
{{Reflist, 2
Virology
Virology
Virology is the Scientific method, scientific study of biological viruses. It is a subfield of microbiology that focuses on their detection, structure, classification and evolution, their methods of infection and exploitation of host (biology), ...