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:
“In history an additional result is commonly produced by human actions beyond that which they aim at and obtain—that which they immediately recognize and desire. They gratify their own interest; but something further is thereby accomplished, latent in the actions in question, though not present to their consciousness, and not included in their design.”
—Georg Wilhelm Friedrich Hegel (1770–1831)
“Regarding History as the slaughter-bench at which the happiness of peoples, the wisdom of States, and the virtue of individuals have been victimized—the question involuntarily arises—to what principle, to what final aim these enormous sacrifices have been offered.”
—Georg Wilhelm Friedrich Hegel (1770–1831)
“Classes struggle, some classes triumph, others are eliminated. Such is history; such is the history of civilization for thousands of years.”
—Mao Zedong (1893–1976)