A Day in the Life of...

Science moves by fits and starts. Sometimes an Einstein or other genius comes along and knowledge advances in a bound or leap. Often though, knowledge progresses in tiny steps. Little is known of the prebiotic world due to planetary and biological evolution which are now intertwined together as one. We know that the atmosphere we have today isn't the original atmosphere. The original atmosphere was primarily nitrogen and carbon dioxide with other trace gases. The earth was an anaerobic world. Where did the oxygen come from to make the present aerobic world? It came from cyanobacteria and simple plant life, algae. As the concentrations of this toxic byproduct of photosynthesis rose, organisms evolved to take advantage of the plant waste and use it for their own energy production. However, oxygen levels didn't rise enough to support complex large multicellular animal life until 500-750 million years ago. That is likely true for plants as well. Plants likely colonized land before animals did.

But what came before it all? When did life arise in the Archean geologic eon? Better yet, where did it arise? The traditional school says that life arose in a warm little pond full of prebiologic precursors. Up until the 1990s, there was no other school of thought. With the discovery in the 1970's of deep sea hydrothermal vents and their continuing analysis, an alternative school of thought arose. One that suggested that hydrothermal vents were the birthplace of early life. (I am a member of that school of thought.) This article suggests that early life arose in a particular type of hydrothermal vents, alkaline hydrothermal vents that have chemical gradients to support a proton driving force for the production of energy. This protonmotive force exists in bacteria, choroplasts, and mitochondria, and is called chemiosmosis, the production of a selective ion gradient (hydrogen protons from water molecules) across a semipermeable membrane. I'm sure that the debate is just getting interesting, but perhaps one day the textbooks will be rewritten to suggest that the first life arose in what we mesophiles would call an underwater hell.

Labels: hydrothermal prebiotic origins