History
For about 100 years, the scientific community has repeatedly changed its collective mind over what viruses are. First seen as poisons, then as life-forms, then biological chemicals, and today many scientists think of viruses as existing at the border between chemistry and life: a gray area between living and nonliving.
The issue of life without cellular structure came again to the fore with the 2003 discovery that the large and complex Mimivirus can synthesize proteins. This discovery suggests the possibility that some viruses may have evolved from earlier forms that could produce proteins independent of a host cell. If so, there may at one time have been a viral domain of life. It is not clear that all small viruses have originated from more complex viruses by means of genome size reduction. A viral domain of life may only be relevant to certain large viruses such as nucleocytoplasmic large DNA viruses like the Mimivirus. A 2012 study suggests that the giant viruses, such as Mimivirus, are a separate domain of life, alongside the traditional three of eukarya, prokarya and archaea, by studying the protein folding structure made by the viruses. The study concluded that giant viruses have evolved from more complex organisms into their highly parasitic form, and are an ancient lineage, alongside that of the other domains.
Viral self-assembly has implications for the study of the origin of life, as it lends further credence to the hypothesis that life could have started as self-assembling organic molecules.
Read more about this topic: Non-cellular Life
Famous quotes containing the word history:
“No cause is left but the most ancient of all, the one, in fact, that from the beginning of our history has determined the very existence of politics, the cause of freedom versus tyranny.”
—Hannah Arendt (1906–1975)
“You that would judge me do not judge alone
This book or that, come to this hallowed place
Where my friends’ portraits hang and look thereon;
Ireland’s history in their lineaments trace;
Think where man’s glory most begins and ends
And say my glory was I had such friends.”
—William Butler Yeats (1865–1939)
“Man watches his history on the screen with apathy and an occasional passing flicker of horror or indignation.”
—Conor Cruise O’Brien (b. 1917)