How and where life first emerged on Earth is one of the great unsolved puzzles for scientists exploring the possibility of life on other worlds. For the past decade or so, the prevailing theory has been that the first primitive organisms originated at alkaline hydrothermal vents in the deep ocean. Now, a new paper by Benjamin Tutolo from the University of Calgary in Canada, published in the Proceedings of the National Academy of Sciences, challenges that assumption.
There’s solid reasoning behind the old paradigm. High temperatures at hydrothermal vents, like the famed Lost City Hydrothermal Field on the Atlantic Ocean floor, are critical for organic molecules to come together to form the all-important biomolecules without which life cannot exist. Sulfide, the reduced form of sulfur used to build cell membranes, was also thought to be plentiful in these deep-ocean environments. It seemed the perfect place for nonliving materials to transform into the first living cell.
But Tutolo argues that the required synthesis reactions would not occur at these vents, because the environment would only become alkaline after it cooled down. Furthermore, reduced sulfur would likely be very sparse in ancient ocean vents. There wouldn’t have been enough time for the chemical reactions necessary to create life to occur before the biological building blocks fell apart again.
The new paper doesn’t completely rule out the hydrothermal vent theory, but it shows that scientists’ favorite scenario for the origin of life on Earth may have serious problems. And it has some researchers taking a second look at other hypotheses that have been proposed — and mostly discarded — in the past.
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