Could life on Earth have begun on land and not in the sea?
A new study, published in PNAS online today argues that the first cells are more likely to have developed in slimy volcanic mud pools, akin to Darwin’s theory that life started in a “warm little pond”.
Recent decades have had Scientists favouring a marine beginning because of the continuous discoveries of life in inhospitable depths. Simple yet hardy bacteria are able to utilize the rich minerals spewing from volcanic vents for chemosynthesis, starting a non-light based food chain and supporting rich hydrothermal vent communities.
Scientists have thought that conditions surrounding these vents could resemble the birth place of cells.
However the new study looked into cellular fluid and found the it is extremely different to ancient ocean water, instead showing a similarity to condensed vapours in volcanic mud pools on land.
Such terrestrial environments boast the high ratios of potassium to sodium found in all living cells. Marine environments, meanwhile, are far too rich in sodium.
"For cells to synthesize proteins—their molecular machines—they need a lot of potassium. Sodium blocks these activities," said study co-author Armen Mulkidjanian, a biophysicist at the University of Osnabrück in Germany.
Cells today rely on complex proteins to pump excess sodium out through their membranes, so the cells can function properly.
The first cells however simply had the luck of the draw. With no complex systems, only rudimentary cellular membranes, these cells simply had to work with the nutrients that were trapped inside.
As a result, the first cells were highly permeable and completely at the mercy of their environments. The ratio of potassium to sodium therefore had to be greater than one to one, in favor of potassium.
But in ancient seawater—as well as in modern seawater—sodium outnumbers potassium 40 to 1.
So the biochemists teamed up with geologists to figure out where these conditions might have occurred between 4.3 and 3.8 million years ago!
The team realized that geothermal fields on land could do the job, particularly the mud pots found in places such as Yellowstone National Park.
"Mud pots are where steam is coming out of the earth and condensing, carrying with it many minerals, including potassium," Mulkidjanian said. "They look like slime coming out of the earth and would make a nice kind of hatchery for the first cells."
Scientists had long ignored mud pots as possible analogs to primordial ooze, because the modern-day versions are swimming in sulfuric acid, a deadly chemical that forms when hydrogen sulfide encounters oxygen in the atmosphere.
"People were scared away by the acidic condition, but Earth used to have very little oxygen in its atmosphere," Mulkidjanian said.
"These anoxic environments were stable over millions of years and were probably conducive to supporting the first life on Earth."
I would like to say something intelligent and meaningful, since this kind of turns everything on it’s head [well that Guinness advert would be wrong now]. So all you’re going to get is ”The Hippopotamus Song [a mud love story]” by Flanders and Swann:-
"Mud, mud, glorious mud, nothing quite like it for
cooling creating the blood”
Adapted from National Geographic