The Evolution of Life I

The possibility that life evolved at hydrothermal vents is very real.  Hydrothermal vents provide an abundance of chemicals at high concentrations.  High concentrations favour chemical interactions more than a vast ocean with low concentrations of chemicals.

Chemosynthesis is a simpler process than photosynthesis where the addition of sunlight is needed to process chemicals to biological compounds.  A simple link can not be found because today vent microbes depend on dissolved oxygen in the water for chemosynthesis.  The oxygen in our present atmosphere has come from photosynthesis.

So what chemical was used instead of oxygen in the chemosynthesis?  The chemical that provides enough energy through simple reactions for the creation of biological compounds is hydrogen gas.  Most vents do emit hydrogen but not in high concentrations.

The higher the concentration the more likely a reaction will occur.  So are their any hydrothermal vents today that emit high concentrations of hydrogen gas?  The recently discovered Rainbow vent field does emit high concentrations of hydrogen.  The high hydrogen concentration is produced by the reaction of the country rock peridotite with the vent water this reaction produces hydrogen gas and a mineral called serpentine.  This is an important because the 4 Gya the a lot more peridotite lava was been produced then in today’s world.  In the early earth, which was a lot more tectonically active we had more hydrothermal vents, and these vent, were producing hydrogen gas.  Hydrogen gas been identified as a likely chemical product been used in chemosynthesis.

Photo of iron reducing bacteria Courtesy of BRIDGE
Sources: K. Condie, BRIDGE

Return to fossil main page