Evidence suggests life on Earth started after meteorites splashed into warm little ponds

October 2, 2017
A figure representing the various influences acting on chemicals in warm little ponds during the dry phase and wet phase of the cycle. Credit: McMaster University

Life on Earth began somewhere between 3.7 and 4.5 billion years ago, after meteorites splashed down and leached essential elements into warm little ponds, say scientists at McMaster University and the Max Planck Institute in Germany. Their calculations suggest that wet and dry cycles bonded basic molecular building blocks in the ponds' nutrient-rich broth into self-replicating RNA molecules that constituted the first genetic code for life on the planet.

The researchers base their conclusion on exhaustive research and calculations drawing in aspects of astrophysics, geology, chemistry, biology and other disciplines. Though the "warm little ponds" concept has been around since Darwin, the researchers have now proven its plausibility through numerous evidence-based calculations.

Lead authors Ben K.D. Pearce and Ralph Pudritz, both of the McMaster's Origins Institute and its Department of Physics and Astronomy, say available evidence suggests that life began when the Earth was still taking shape, with continents emerging from the oceans, meteorites pelting the planet - including those bearing the of life - and no protective ozone to filter the Sun's ultraviolet rays.

"No one's actually run the calculation before," says Pearce. "This is a pretty big beginning. It's pretty exciting."

"Because there are so many inputs from so many different fields, it's kind of amazing that it all hangs together," Pudritz says. "Each step led very naturally to the next. To have them all lead to a clear picture in the end is saying there's something right about this."

Their work, with collaborators Dmitry Semenov and Thomas Henning of the Max Planck Institute for Astronomy, has been published today in the Proceedings of the National Academy of Science.

"In order to understand the origin of life, we need to understand Earth as it was billions of years ago. As our study shows, astronomy provide a vital part of the answer. The details of how our solar system formed have direct consequences for the origin of life on Earth," says Thomas Henning, from the Max Planck Institute for Astronomy and another co-author.

Photo of a warm little pond on present day Earth on the Bumpass Hell trail in Lassen Volcanic National Park in California. Credit: Ben K.D. Pearce, McMaster University

The spark of life, the authors say, was the creation of RNA polymers: the essential components of nucleotides, delivered by meteorites, reaching sufficient concentrations in pond water and bonding together as water levels fell and rose through cycles of precipitation, evaporation and drainage. The combination of wet and dry conditions was necessary for bonding, the paper says.

In some cases, the researchers believe, favorable conditions saw some of those chains fold over and spontaneously replicate themselves by drawing other nucleotides from their environment, fulfilling one condition for the definition of life. Those polymers were imperfect, capable of improving through Darwinian evolution, fulfilling the other condition.

"That's the Holy Grail of experimental origins-of-life chemistry," says Pearce.

That rudimentary form of life would give rise to the eventual development of DNA, the genetic blueprint of higher forms of life, which would evolve much later. The world would have been inhabited only by RNA-based life until DNA evolved.

"DNA is too complex to have been the first aspect of life to emerge," Pudritz says. "It had to start with something else, and that is RNA."

The researchers' calculations show that the necessary conditions were present in thousands of ponds, and that the key combinations for the formation of life were far more likely to have come together in such ponds than in hydrothermal vents, where the leading rival theory holds that life began in roiling fissures in ocean floors, where the elements of life came together in blasts of heated water. The authors of the new paper say such conditions were unlikely to generate life, since the bonding required to form RNA needs both wet and dry cycles.

The calculations also appear to eliminate space dust as the source of life-generating nucleotides. Though such dust did indeed carry the right materials, it did not deposit them in sufficient concentration to generate life, the researchers have determined. At the time, early in the life of the solar system, meteorites were far more common, and could have landed in thousands of ponds, carrying the building blocks of life.Pearce and Pudritz plan to put the theory to the test next year, when McMaster opens its Origins of Life laboratory that will re-create the pre- conditions in a sealed environment.

"We're thrilled that we can put together a theoretical paper that combines all these threads, makes clear predictions and offers clear ideas that we can take to the laboratory," Pudritz says.

Explore further: Studying the roots of life

More information: Ben K. D. Pearce el al., "Origin of the RNA world: The fate of nucleobases in warm little ponds," PNAS (2017). www.pnas.org/cgi/doi/10.1073/pnas.1710339114

Related Stories

Studying the roots of life

March 25, 2011

With a space telescope churning out discoveries of new planets, robots exploring Mars and other places, and researchers gaining understanding of extreme environments, the search for the roots of life on Earth and other planets ...

How RNA formed at the origins of life

May 19, 2017

A single process for how a group of molecules called nucleotides were made on the early Earth, before life began, has been suggested by a UCL-led team of researchers.

Recommended for you

Carbon coating gives biochar its garden-greening power

October 20, 2017

For more than 100 years, biochar, a carbon-rich, charcoal-like substance made from oxygen-deprived plant or other organic matter, has both delighted and puzzled scientists. As a soil additive, biochar can store carbon and ...

Cool roofs have water saving benefits too

October 20, 2017

The energy and climate benefits of cool roofs have been well established: By reflecting rather than absorbing the sun's energy, light-colored roofs keep buildings, cities, and even the entire planet cooler. Now a new study ...

11 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

omegatalon
4.3 / 5 (3) Oct 02, 2017
Or as the Ancient Aliens folks will tell you that aliens came to earth and decided to play god.
mj002
3.3 / 5 (7) Oct 02, 2017
Here we are, learning about this just before human life goes extinct. Isn't that always the way, a day late and a dollar short.
Parsec
4.3 / 5 (9) Oct 02, 2017
Here we are, learning about this just before human life goes extinct. Isn't that always the way, a day late and a dollar short.


While it is certainly foreseeable that the earth's human population will go through bottlenecks of dramatic reduction at various times in the future, it is difficult to imagine any event that would lead to actual extinction.
Nik_2213
4.3 / 5 (4) Oct 02, 2017
"...it is difficult to imagine any event that would lead to actual extinction."

Please try harder. Toba's 70k BPE super-eruption came close, such now would be worse. A new 'Large Igneous Province' such as the 'Siberian Traps' that seems to have caused the Permian mega-extinction would be horrendous.

Meteor Crater was made by an estimated 50 metre diameter impactor. A sub-kilometre rock hitting eg Arabia with scant warning may prompt the 'Usual Suspects' to launch nukes, either in mistaken retaliation or 'beggar my neighbour' mode. Then, as refugees flee hither & yon, expect dire diseases to run amok as the disaster cascades through global society...
Brrr...
aksdad
3.3 / 5 (6) Oct 02, 2017
The spark of life, the authors say, was the creation of RNA polymers

Except that RNA and the more complex DNA are simply inanimate molecules. They are the instructions for cellular replication, akin to the combinations of binary bits encoded on a magnetic or optical disk that are instructions for digital microprocessors. Without a microprocessor to read and perform the instructions, the bits by themselves accomplish nothing.

DNA and RNA are just molecular data. Without cellular machinery to process them, they can do nothing. The lengthy and non-random digital bits that contain microprocessor instructions are evidence that some deliberate intelligent process (a human) created them. In the same way, DNA and RNA are evidence that some deliberate intelligent process (cellular mitosis) created them, but they are nevertheless as inanimate as the digital bits on an optical disk or a flash drive.
SuchNessNone
3.7 / 5 (3) Oct 02, 2017
"[..] it is difficult to imagine any event that would lead to actual extinction." - Not so.. if the earth happens to collide with the likes of the most recent comet to hit Jupiter. Game over. .
Shootist
2 / 5 (1) Oct 02, 2017
"[..] it is difficult to imagine any event that would lead to actual extinction." - Not so.. if the earth happens to collide with the likes of the most recent comet to hit Jupiter. Game over. .


At 1.4 km diameter, Shoemaker-Levy 9 was nowhere near large enough to cause an extinction event. The Chixiulub bolide was ~10 km in diameter depending on composition.

http://adsabs.har...22..155C

Zzzzzzzz
3.7 / 5 (3) Oct 02, 2017
Life on this planet is robust, and could not be extinguished while the sun still lives. Humans? They could be gone very easily. Humans might well manage to drown in their own waste products, like yeast.
TrollBane
not rated yet Oct 03, 2017
"Life on this planet is robust, and could not be extinguished while the sun still lives." The sun will still be 'alive' when it expands and cooks Earth, and if it does engulf Earth, even subterranean microbes will be 'toast'.
djacob789
1 / 5 (1) Oct 05, 2017
Nik_2213 "Please try harder."
Could we try and be more polite here so it won't go as low as Youtube comments?
barakn
4.5 / 5 (2) Oct 06, 2017
Except that RNA and the more complex DNA are simply inanimate molecules. They are the instructions for cellular replication, akin to the combinations of binary bits encoded on a magnetic or optical disk that are instructions for digital microprocessors. Without a microprocessor to read and perform the instructions, the bits by themselves accomplish nothing.
RNA can modify itself or catalyze many other chemical reactions. "The condensation of amino acids in the peptidyl transferase center of the ribosome (arguably THE most important reaction in the cell!) is catalyzed not by protein, but by the major RNA component of the large subunit. " https://www.ncbi....4371269/
Please apologize for lying to everyone, aksdad.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.