Thursday, April 10, 2014

Theory on the origin of life put to the test... and failed

An underwater probe samples fluids from a hydrothermal
vent deep in the ocean.  Credit: Chris German, Woods Hole
Oceanographic Institution.  Image source.
Making life is hard.  Correction: making life from non-life is hard.  In fact, many people consider it to be impossible.  Famous biologist Louis Pasteur even developed the Law of Biogenesis, which states that life can only come from other life.  Yet, anyone with a materialistic naturalistic worldview must conclude that life arose from nonliving matter at some point in the past, lest they consider it eternal.  Explaining how exactly this may have happened seems to be quite a feat for them, however.  Most honest naturalistic scientists will admit that the origin of life remains a mystery.

Of course, the scientific community generally dislikes leaving anything unexplained, so numerous hypotheses have been proposed in attempt to puzzle out the mystery of abiogenesis.  Currently, the most favored explanations involve hydrothermal vents at the bottom of the ocean, where mineral-rich water heated by magma flows into the cold marine waters.  Today, these environments host numerous organisms, providing substantial heat and raw materials far away from the damaging radiation of the sun.  Many scientists believe this to be the most likely place for the first lifeforms to have arisen.

Even then, however, there are several schools of thought as to how exactly the life came about.  The main point of contention is which aspect of the living cell formed first.  Did complex genetic material arise from chemical reactions, as in the "RNA World" hypothesis, or did proteins have to be present before that to catalyze the reactions?  Perhaps RNA and proteins formed simultaneously, as was proposed in October.  Other scientists propose that metabolism itself came first, starting a complex chemical reaction that continues today as life.

The "metabolism first" hypothesis intrigued a few geochemists from Woods Hole Oceanographic Institution, who decided to test one of its critical aspects.  The hypothesis suggests that certain complex chemicals necessary to begin the metabolic process could naturally be formed around hydrothermal vents, particularly a gas called methanethiol (CH3SH).  The geochemists endeavored to sample modern hydrothermal vents to determine whether methanethiol can form by purely chemical means.

After sampling numerous hydrothermal sites from the Atlantic and Pacific Oceans over a period of four years, the scientist found that, indeed, methanethiol was present at many of the vents.  However, the distribution of the methanethiol surprised them, completely overturning their predictions.  They had expected to find more methanethiol where hydrogen concentrations were highest, yet it was found in the low-hydrogen and relatively low-temperature environments.  Based on other chemical clues, such as the presence of ammonia, the team concluded that the methanethiol was being formed from the breakdown of previously living matter rather than from nonliving chemicals.  As it turned out, formation of methanethiol is more chemically difficult than the scientists had initially suspected.

Although this study strikes down one specific version of the abiogenesis hypothesis, it does not disprove abiogenesis as a whole.  Most researchers still maintain that hydrothermal vents are the most likely place for life to have begun; it just apparently happened without methanethiol.  As for the team of geochemists, they say that their results can still be useful for detecting life on other planets.  Good luck with that, I say.

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