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Why Scientists Think Completely Unclassifiable and Undiscovered Life Forms Exist
An anonymous reader writes: In a new paper published in Science, researchers at the Department of Energy's Joint Genome Institute note that "there are reasons to believe that current approaches [to discovering life] may indeed miss taxa, particularly if they are very different from those that have so far been characterized." They believe life forms exist that don't fall into the established eukaryota, archaea, or bacteria kingdoms. They argue that there may be life out there that doesn't use the four DNA and RNA bases that we're used to; there may be life out there that has evolved completely separately from everything that we have ever known to exist; there may be life that lives in places we haven't even looked.
Historically, "Life" has been defined as being any phenomenon that possesses all 5 life processes:
#1 Food intake/ nutrition
#2 Respiration
#3 Excretion
#4 Growth & Repair
#5 Reproduction
However, this seems to have been expanded to 7:
#1 Movement
#2 Respiration
#3 Sensitivity
#4 Growth
#5 Excretion
#6 Reproduction
#7 Nutrition
This is for "Life" in the generalized sense, fully abstracted away from any specific mechanisms by which those processes may be achieved. It is perfectly sensible for an artificial lifeform to be constructed, as long as it is able to fully carry out those processes. It needn't have any organic components whatsoever.
Nowhere in the historical definition of "life" used by life science is there a requirement for specific mechanisms-- just processes.
What they mean by the term is "not fitting existing classifications" of course.