Many of life’s most interesting questions are about the boundaries between things.
- Where does a white lie become just a lie?
- Where does art become non-art?
- Where does innocence become ignorance?
- Where does charity become enablement?
Perhaps the most interesting boundary question of all is, where does life become nonlife? Here’s a list of …um… things. Where would you draw that boundary?
Archaea — Even simpler than bacteria, archaea have no membrane-bound organelles. They are famous for their variety, with some able to live in environments previously thought uninhabitable, or obtain energy from inorganic sources such as sulfur or ammonia.
Viruses — A virus has genetic material (either DNA or RNA), a protein coat, and sometimes an envelope that helps the virus identify and enter the cells it infects. Viruses reproduce (big-time) but they do not have their own metabolism, instead hijacking the metabolism of their hosts.
Prions — A prion is nothing more than a badly folded protein. Unlike bacteria and viruses, it has no DNA or RNA. However, it does reproduce, vampire-fashion, by converting well-folded proteins to misfolded ones, which go on to convert others. Prion structures even “grow” by forming fibrils that extend at each end. Prions are in the cause of nasty-sounding illnesses including mad cow disease, chronic wasting disease and scrapie.
Organic molecules from outer space — Amino acids, well-known as the building blocks of life as we know it, have been found on meteors. Cool, right?
Surely by the end of that list we have arrived at nonlife. But when did we make the transition?
Before 1828, scientists believed that the chemistry of living things differed from that of nonliving things. That notion has been thoroughly refuted and now “organic chemistry” simply means chemistry that involves carbon.
That ball has continued to roll, and now the distinction between life itself and nonlife is far from clear.
It makes you wonder…