What Is Life? (2019)
My own personal definition of life is the following, somewhat hand-wavy, theoretically weak, though pragmatically strong definition:<p><i>Life is anything capable of sloppy self-replication in a sufficiently complex environment.</i><p>Viruses are <i>definitely</i> alive.  Something like Tierra [1], Avida[2], or modern variants[3] of mutating copying programs come close, giving rise to whole ecosystems of parasites and hosts and defenses, etc. though perhaps they are lacking the &quot;sufficient complexity&quot; necessary so as not to stall out and stop evolving much. Chemistry provides such a massive environment of complexity that it&#x27;s hard to replicate elsewhere, though I&#x27;d argue it&#x27;s hardly impossible.<p>The problem with this article&#x27;s definition is that, with near certainty, the first progenitor lifeform on earth did NOT utilize ANY of the DNA&#x2F;RNA protein translation machinery they state are necessary to meet their definition of alive.  You can find some surpringly good statistical analyses of this assertion in an unlikely ally: creationist statistical arguments.  They prove pretty definitively that life didn&#x27;t begin with a transcriptase protein popping into existence.<p>What are the problems with my definition:<p>The big theoretical hole: You could concoct some hypothetical scenario where something I&#x27;d definitely agree is alive replicates using some star trek technology that doesn&#x27;t allow for the &quot;sloppy&quot; part.  W&#x2F;e, I consider this pragmatically irrelevant.<p>The second big objection: It allows us to consider many things as &quot;alive&quot; that most would say are not.  In my opinion, this is actually a major strength.<p>Ok, but what about things like crystals?  
Personally, I consider some type of self-catalysing crystal or quasicrystal to be one of the most plausible forms of original life on earth.  That said, they seem to be lacking the &quot;sufficient complexity&quot; aspect.  However, are they really?  I&#x27;m not so sure.  Is it possible for a particular pattern of crystal defects to bring about a replication of sorts of that defect pattern elsewhere in the crystal during crystallization?  That may be enough complexity particularly when you consider substitutions (when one element in the crystal lattice gets swapped for another).  If some type of pattern of crystal defects or quasicrystal or something developed sufficient self-catalysing ability to bring about a form of sloppy self-replication, it&#x27;s likely that&#x27;s enough for life provided that the environment allows it under entropy considerations.<p>[1]<a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Tierra_(computer_simulation)" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Tierra_(computer_simulation)</a>
[2]<a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Avida" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Avida</a>
[3]<a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Artificial_life" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Artificial_life</a>