Are viruses alive? New evidence says yes
Evolutionary history suggests they evolved from ancient cells
By Grennan Milliken September 25, 2015
Guess the next question would be, what difference does it make?
That article posits biochemical similarities between viruses and cells “suggests that viruses were not simply shed genetic material of cells, but shared unique properties with cells (and thus were living) and eventually evolved as separate entities.” It seems to me that viruses probably descended from cells rather than originating independently (that is, rather than there having been no universal common ancestor). We can find viral gene segments in the human genome, and it seems like every living cell across all three domains can be infected by at least one virus. But is it reasonable to conclude that because viruses and cells co-evolve/d, viruses are living? Maybe a better question is, should the capacity to actively self-replicate be necessary to consider something living. It seems like a trivial argument at first glance, but maybe it has implications in understanding the origins of life and the search for extraterrestrial organisms.
Biologists debate whether viruses should be considered living organisms, partly because the term “living” is difficult to define. Is the debate simply semantics, or is it consequential?
IMO, viruses are a hybrid, somewhere between purely chemical, yet being able to act as parasitic organism.
A missing link between inanimate and animate?
You bring up an interesting point - it’s hard to distinguish physics from chemistry from biology because lower levels of organization produce higher ones. Atoms form molecules that undergo chemical processes that we call metabolism. Viruses are not metabolically active outside of a cell. Your use of the word “organism” suggests you consider viruses living once they infect a cell, since an organism can be defined as a discrete living individual. But do viruses become metabolically active once inside cells, or are they still passive?
You reworded the question nicely. Of course these are big open questions but it’s an interesting discussion.