November 14, 2008 | David F. Coppedge

Poison Planet Was Life’s Training Ground

Navy Seals go through “Hell Week” in their training to become warriors.  The radical hardships they endure help prepare them for missions that will call on their deepest resources of courage and determination.  These men of the elite special forces also become experts in dealing with explosives.  Can molecules do the same, with a little training?  Dr. Friedemann Freund of the SETI Institute believes that deadly poisons in the early earth gave emerging life a Hell Week of billions of years to prepare them for existence with the most reactive element in the air: oxygen.
    Dr. Freund’s article for SETI Thursday on, might turn off the casual reader due to the chemical equations and the technical analysis of hydroxyls, peroxides and banded iron formations.  He did start it with a teaser line, though: “Living on a planet with an oxygen-rich atmosphere we tend to forget that our planet is an anomaly.”  The chemistry details were provided to demonstrate that early life would have had to deal with reactive oxygen species (ROS), including peroxides.  These energetic molecules rip and tear into biological molecules like DNA and protein.  Many readers may have quit before the interesting part at the end.  That’s where Dr. Freund intimated that a little Hell Week training gave life the ability to deploy oxygen in metabolism – without getting blown up in the process.

Thus we come to the tentative conclusion that, through weathering and electrochemistry, peroxy in rocks provided enough oxidation power to change the course of our planet’s history.  Over the course of 1.5 to 2 billion years, peroxy forced the early Earth to slowly but inextricably become ever more oxidized.  Along the way dangerous Reactive Oxygen Species [ROS], constantly produced at rock-water interfaces and during peroxy hydrolysis, challenged the early microbes, archaea and bacteria.  As Dr. Rothschild so aptly put it, the ROS might have provided a “training ground” for those early micro-organisms to learn how to deal with oxygen.  They developed the basic enzymatic defenses, which our bodies still use today to fend off the detrimental side effects of our oxygen-based metabolism.
    Thus, while the Earth was still overwhelmingly reduced [i.e., oxygen-depleted], eukaryotes joined the archaea and bacteria.  Under the onslaught of those ROS, the eukaryotes “learned” how to survive in an oxygen-spiked environment long before free O2 gas appeared in Earth’s atmosphere.  At some point the eukaryotes learned how to take advantage of the large chemical energy that oxygen can provide.  They adapted to do oxygenic photosynthesis, to tap the energy in O2.  This lead [sic] to the Great Oxidation Event and to plenty of free O2 in Earth’s atmosphere that made our planet livable for us…and it all started with water and a little-known solid state reaction in the rocks.

It seems ironic that after Dr. Freund had employed chemical equations based on the laws of chemistry that he would end up imagining molecules overcoming those same natural laws through the exercise of courage and determination.  And regarding oxygenic photosynthesis, a process so elaborate that today’s biochemists struggle to comprehend it, he imagined the earliest eukaryotes had a simple motto: Just do it.  The Navy Seals have quite a different motto: The only easy day was yesterday.

Sometimes the comments in an article do all the work of commentary for us.  You didn’t realize that simple cells have all the courage, determination and ingenuity of elite special forces, did you?  Sure; they face their challenges, adapt, learn and develop protocols for handling explosives, all without a brain or a purpose.  Maybe the SETI Institute people need to search for a little extra-terrestrial intelligence about five feet above the terrestrial surface they are standing on.

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