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The Discovery of the Third Domain of Life

In 1977, Carl Woese overturned one of the major dogmas of biology. Until that time, biologists had taken for granted that all life on Earth belonged to one of two primary lineages:
* the eukaryotes (which include animals, plants, fungi and certain unicellular organisms such as paramecium)
* and the prokaryotes (all remaining microscopic organisms).

Woese discovered that there were actually three primary lineages. Within what had previously been called prokaryotes, there exist two distinct groups of organisms no more related to one another than they were to eukaryotes.

Because of Woese’s work, it is now widely agreed that there are three primary divisions of living systems – the Eukarya, Bacteria, and Archaea, a classification scheme that Woese proposed in 1990.

….In 1996, Woese and colleagues (University of Illinois professor Gary Olsen and researchers from the Institute for Genomic Research) published in the journalScience the first complete genome structure of an archaeon, Methanococcus jannaschii.

Based on this work, they concluded that the Archaea are more closely related to humans than to bacteria. “The Archaea are related to us, to the eukaryotes; they are descendants of the microorganisms that gave rise to the eukaryotic cell billions of years ago,” Woese said at the time.



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