Our ultimate ancestor may have been a virus, according to the intriguing cover article in this month’s Discover magazine.
Until recently, viruses were considered to be a latecomer in the scheme of life, a form of opportunistic, quasi-living entity that uses other organisms to reproduce. With the discovery of a comparatively large, more complex virus, named Mimivirus, biologists are now wondering if viruses actually predate the hosts they invade, and sometimes kill.
There are three domains of living organisms currently recognized by biology: eukaryotes, which have nuclei in their cells and include plants and animals, bacteria, single-celled organisms which may or may not have nuclei, and archaea, “extremist” microbes without nuclei. Viruses were considered to be more chemical assemblages than biological entities — basically not part of the “tree of life.”
Now it seems viruses are more complex and older than previously thought, and may warrant being added as a fourth domain of organisms. Viruses may have also interacted with bacteria and archaea in the dim past to form the first eukaryotes, which eventually evolved into human beings.
So, welcome your distant cousin, influenza, to your family tree. Hopefully, it won’t pay you a surprise visit at the next family reunion.
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