Earth started as a violent place, its surface churned by continuous volcanic eruptions and cloaked in an atmosphere that would have been poisonous to today's life-forms. Furthermore, the thin primeval atmosphere may have provided only scant protection from the young sun's harsh ultraviolet glare. Given these inhospitable conditions, scientists have long wondered: How did the first cells come to be nearly four billion years ago?

Conventional scientific wisdom holds that life arose in the sea. But a new study suggests that the first cells—or at least the ones that left descendants still extant—got their start in geothermal pools, like those seen at Yellowstone National Park and other geologic hot spots today. The argument rests on one indisputable observation—enzymes common to all archaea and bacteria are built from potassium, phosphorus or zinc, not sodium.

Some biologists suspect that the membranes of early life-forms were not yet the tight coverings that they are today, and would have instead let small molecules and ions flow in and out freely. If life arose in the salty sea, then the first cells and their living relatives might be expected to have enzymes built from abundant sodium—or at least tolerate more sodium internally. That modern archaea and bacteria instead possess internal fluid low in sodium, and enzymes built from other elements hints that they arose in an environment both rich in such elements as well as relatively sodium-free. "If the very first membranes were leaky for small molecules and ions, then the interior of the first cells should have been in equilibrium with their surroundings," explains biophysicist Armen Mulkidjanian of the University of Osnabrück in Germany, lead author of the paper presenting the hypothesis published online February 13 in Proceedings of the National Academy of Sciences. "By reconstructing the inorganic chemistry of the cytoplasm, it might be possible to reconstruct the habitats where the first cells could dwell."

The team noted that most modern cells maintain a high ratio of potassium ions to sodium ions. "We looked all over the place for the conditions and processes that would lead to [potassium] enrichment," Mulkidjanian says. The only such places extant today are so-called "vapor-dominated" geothermal systems—locales where water, heated deep within Earth until it becomes steam, reaches the surface, cools and condenses back to elementally enriched liquid pools. Condensed geothermal steam in these pools can have ratios of potassium to sodium ions as high as 75 to 1, and are rich in the other elements of life that have been leached from rock by the hot water. Thus, Mulkidjanian and his colleagues argue that they may have been the "hatcheries" of the first cells.

The argument matches a perhaps prescient suggestion from Charles Darwin in an 1871 letter: "But if (and oh what a big if) we could conceive in some warm little pond with all sorts of ammonia and phosphoric salts, light, heat, electricity, etcetera present that a protein compound was chemically formed, ready to undergo still more complex changes." Nobel laureate and geneticist Jack Szostak of Harvard University has also argued that the first cells probably had leaky membranes and that early oceans were not a favorable environment for the origin of life.

6 Comments

1. 1. thekenyanpaul 07:02 AM 2/16/12

   What crap! There are thousands of geothermal vents worldwide, have they found any of these thin-membraned leaky bacteria yet? This is pseudo-science in overdrive! No evidence at all but wild speculation like the ancient philosophers...

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2. 2. Bill Crofut 11:53 AM 2/16/12

   Re: "The argument matches a perhaps prescient suggestion from Charles Darwin in an 1871 letter: "But if (and oh what a big if) we could conceive in some warm little pond with all sorts of ammonia and phosphoric salts, light, heat, electricity, etcetera present that a protein compound was chemically formed, ready to undergo still more complex changes."
   
   The quote seems to have been truncated:
   
   It is often said that all the conditions for the first production of a living organism are now present, which could ever have been present.— But if (& oh what a big if) we could conceive in some warm little pond with all sorts of ammonia & phosphoric salts,—light, heat, electricity &c present, that a protein compound was chemically formed, ready to undergo still more complex changes, at the present day such matter wd be instantly devoured, or absorbed, which would not have been the case before living creatures were formed. [Letter to J. D. Hooker, 1 Feb [1871]
   
   http://www.darwinproject.ac.uk/editors-blog/2012/02/15/darwins-warm-little-pond/
   
   At least one attempted experiment would seem to have been less than successful:
   
   http://www.ucsc.edu/news_events/press_releases/text.asp?pid=837
   
   Re: "Of course, the early Earth's atmosphere lacked oxygen, instead it was rich in other gases, such as hydrogen sulfide."
   
   This claim has met with some opposition:
   
   "Geological evidence often presented in favor of an early anoxic atmosphere is both contentious and ambiguous. The features that should be present in the geological record had there been such an atmosphere seem to be missing....Ever since the work of Oparin…and the success of the experiments conducted by Miller...the dogma has arisen that Earth’s early atmosphere was anoxic, probably highly reducing...Conjecture and speculation, based on a knowledge of the chemistry of living matter, gave to them the composition of their starting materials, and it would have been surprising if they had not achieved the results they did."
   [Harry Clemmey and Nick Badham. 1982. Oxygen in the Precambrian Atmosphere: An Evaluation of the geological Evidence. GEOLOGY, March, p. 141]

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3. 3. elderlybloke 02:42 PM 2/16/12

   According to what I have learned about the history of Oxygen, it was the work of Cyanobacteria ,slowly building it up over a billion or so years and leaving the former anoxic loving life with only a few homes(like Hot Springs).

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4. 4. Bill Crofut 10:16 AM 2/18/12

   Geologists Clemmy and Badham would seem to be indicating the presence of oxygen in the
   
   atmosphere of the Earth from the beginning (i.e., not biologically manufactured).

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5. 5. poihths in reply to thekenyanpaul 09:53 PM 2/22/12

   Fundamental misunderstanding is rarely a sound basis for comment. The whole point is that the early leaky critters kept on developing and became the non-leaky critters we find today. In other words, they managed to change a little bit during the last blink-of-an-eye three billion years.

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6. 6. charwiz in reply to thekenyanpaul 06:08 PM 2/26/12

   
   Although hydrothermal vents are what we would consider a harsh environment, they are teeming (abundant) with life. As long as the vents remain active, which is usually one to two years, animals thrive there. In fact, more than 300 species live around the vents and are unique to this type of environment. These creatures, including tubeworms, fish, crabs, shrimp, clams, anemones and chemosynthetic bacteria, have learned to survive the complete darkness, the extremely hot vent water and the tremendous water pressure.
   
   charwiz
   charwiz2005@yahoo.com
   
   
   
   
   
   
   
   
   http://www.onr.navy.mil/focus/ocean/habitats/vents2.htm

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