Post by FilmFlaneur on Oct 4, 2017 9:39:48 GMT
A recent report from science's continuing investigation into the causes of life.
Proceedings of the National Academy of Sciences of the United States of America PNAS
Origin of the RNA world: The fate of nucleobases in warm little ponds
Ben K. D. Pearcea,b,1, Ralph E. Pudritza,b,c,d, Dmitry A. Semenovc, and Thomas K. Henningc
Author Affiliations:
a Origins Institute, McMaster University, Hamilton, ON L8S 4M1, Canada;
b Department of Physics and Astronomy, McMaster University, Hamilton, ON L8S 4M1, Canada;
c Planet and Star Formation Department, Max Planck Institute for Astronomy, 69117 Heidelberg, Germany;
d Institute for Theoretical Astrophysics, Center for Astronomy Heidelberg, 69120 Heidelberg, Germany
Edited by Donald E. Canfield, Institute of Biology and Nordic Center for Earth Evolution, University of Southern Denmark, Odense M., Denmark, and approved August 28, 2017 (received for review June 7, 2017)
Abstract :
There are currently two competing hypotheses for the site at which an RNA world emerged: hydrothermal vents in the deep ocean and warm little ponds. Because the former lacks wet and dry cycles, which are well known to promote polymerization (in this case, of nucleotides into RNA), we construct a comprehensive model for the origin of RNA in the latter sites. Our model advances the story and timeline of the RNA world by constraining the source of biomolecules, the environmental conditions, the timescales of reaction, and the emergence of first RNA polymers.
Before the origin of simple cellular life, the building blocks of RNA (nucleotides) had to form and polymerize in favorable environments on early Earth. At this time, meteorites and interplanetary dust particles delivered organics such as nucleobases (the characteristic molecules of nucleotides) to warm little ponds whose wet–dry cycles promoted rapid polymerization. We build a comprehensive numerical model for the evolution of nucleobases in warm little ponds leading to the emergence of the first nucleotides and RNA. We couple Earth’s early evolution with complex prebiotic chemistry in these environments. We find that RNA polymers must have emerged very quickly after the deposition of meteorites (less than a few years). Their constituent nucleobases were primarily meteoritic in origin and not from interplanetary dust particles. Ponds appeared as continents rose out of the early global ocean, but this increasing availability of “targets” for meteorites was offset by declining meteorite bombardment rates. Moreover, the rapid losses of nucleobases to pond seepage during wet periods, and to UV photodissociation during dry periods, mean that the synthesis of nucleotides and their polymerization into RNA occurred in just one to a few wet–dry cycles. Under these conditions, RNA polymers likely appeared before 4.17 billion years ago.
Life on Earth began not with humans, but with meteorites and warm little ponds, according to recent research. That life began somewhere between 3.7 and 4.5 billion years ago as meteorites splashed into ponds, leaching their essential elements and contributing to life on Earth. It appears Charles Darwin may be correct when he hypothesized that life began in a ‘warm little pond’ during the early stages of Earth. In 1871, Charles Darwin wrote that life could have evolved in ‘some warm little pond’ going on to say that it would have to be concentrated in ‘ammonia, phosphoric salts, light, heat, and electricity’.
There are certainly competing hypotheses, one that suggests life may have begun from hydrothermal vents on the ocean floor and evolving to land-based life 2.9 billion years ago. However, recent evidence reveals that life on Earth may have occurred much earlier and from a different mechanism: meteorites. In the early stages of Earth, carbon-rich meteorites rained down from the sky. Some of those meteorites landed in small warm ponds, where essential elements were dissolved into the ponds. The ponds would have had wet and dry cycles, which allowed the nutrient-rich broth to concentrate into self-replicating RNA. These RNA molecules were the first genetic material on Earth and the basis for all life thereafter.
The study, published in the Proceedings of the National Academy of Science, was conducted by a research team from the Max Planck Institute for Astronomy. The team found that in order to promote polymerization of nucleotides into RNA, you must have wet and dry cycles. These cycles likely did not exist in hydrothermal vents at the seafloor.
In order to form RNA, nucleotides had to polymerize and a perfect environment for that to happen is a small warm pond. The study proposes that RNA likely formed after just one or a couple wet to dry cycles in the ponds and that RNA first appeared 4.17 billion years ago or earlier. The formation of RNA would have eventually led to the evolutionary development of DNA, the blueprint for life as we know it on Earth today. However, until that happened, RNA based life existed on Earth, which is much more simple than DNA.
The research team plans to put their calculations to text. They plan to recreate these early life conditions in a laboratory which mimics meteorites splashing into warm little ponds. This will allow the researchers further testing of their hypothesis and build evidence toward a warm little pond origin of life. This exciting research provides a significantly different view on how life originally formed on Earth and could advise on where and how life could exist on other planets. www.forbes.com/sites/trevornace/2017/10/03/life-on-earth-began-with-splashing-meteorites-and-warm-little-ponds-study-suggests/
There are certainly competing hypotheses, one that suggests life may have begun from hydrothermal vents on the ocean floor and evolving to land-based life 2.9 billion years ago. However, recent evidence reveals that life on Earth may have occurred much earlier and from a different mechanism: meteorites. In the early stages of Earth, carbon-rich meteorites rained down from the sky. Some of those meteorites landed in small warm ponds, where essential elements were dissolved into the ponds. The ponds would have had wet and dry cycles, which allowed the nutrient-rich broth to concentrate into self-replicating RNA. These RNA molecules were the first genetic material on Earth and the basis for all life thereafter.
The study, published in the Proceedings of the National Academy of Science, was conducted by a research team from the Max Planck Institute for Astronomy. The team found that in order to promote polymerization of nucleotides into RNA, you must have wet and dry cycles. These cycles likely did not exist in hydrothermal vents at the seafloor.
In order to form RNA, nucleotides had to polymerize and a perfect environment for that to happen is a small warm pond. The study proposes that RNA likely formed after just one or a couple wet to dry cycles in the ponds and that RNA first appeared 4.17 billion years ago or earlier. The formation of RNA would have eventually led to the evolutionary development of DNA, the blueprint for life as we know it on Earth today. However, until that happened, RNA based life existed on Earth, which is much more simple than DNA.
The research team plans to put their calculations to text. They plan to recreate these early life conditions in a laboratory which mimics meteorites splashing into warm little ponds. This will allow the researchers further testing of their hypothesis and build evidence toward a warm little pond origin of life. This exciting research provides a significantly different view on how life originally formed on Earth and could advise on where and how life could exist on other planets. www.forbes.com/sites/trevornace/2017/10/03/life-on-earth-began-with-splashing-meteorites-and-warm-little-ponds-study-suggests/
Abstract from the new study:
Proceedings of the National Academy of Sciences of the United States of America PNAS
Origin of the RNA world: The fate of nucleobases in warm little ponds
Ben K. D. Pearcea,b,1, Ralph E. Pudritza,b,c,d, Dmitry A. Semenovc, and Thomas K. Henningc
Author Affiliations:
a Origins Institute, McMaster University, Hamilton, ON L8S 4M1, Canada;
b Department of Physics and Astronomy, McMaster University, Hamilton, ON L8S 4M1, Canada;
c Planet and Star Formation Department, Max Planck Institute for Astronomy, 69117 Heidelberg, Germany;
d Institute for Theoretical Astrophysics, Center for Astronomy Heidelberg, 69120 Heidelberg, Germany
Edited by Donald E. Canfield, Institute of Biology and Nordic Center for Earth Evolution, University of Southern Denmark, Odense M., Denmark, and approved August 28, 2017 (received for review June 7, 2017)
Abstract :
There are currently two competing hypotheses for the site at which an RNA world emerged: hydrothermal vents in the deep ocean and warm little ponds. Because the former lacks wet and dry cycles, which are well known to promote polymerization (in this case, of nucleotides into RNA), we construct a comprehensive model for the origin of RNA in the latter sites. Our model advances the story and timeline of the RNA world by constraining the source of biomolecules, the environmental conditions, the timescales of reaction, and the emergence of first RNA polymers.
Before the origin of simple cellular life, the building blocks of RNA (nucleotides) had to form and polymerize in favorable environments on early Earth. At this time, meteorites and interplanetary dust particles delivered organics such as nucleobases (the characteristic molecules of nucleotides) to warm little ponds whose wet–dry cycles promoted rapid polymerization. We build a comprehensive numerical model for the evolution of nucleobases in warm little ponds leading to the emergence of the first nucleotides and RNA. We couple Earth’s early evolution with complex prebiotic chemistry in these environments. We find that RNA polymers must have emerged very quickly after the deposition of meteorites (less than a few years). Their constituent nucleobases were primarily meteoritic in origin and not from interplanetary dust particles. Ponds appeared as continents rose out of the early global ocean, but this increasing availability of “targets” for meteorites was offset by declining meteorite bombardment rates. Moreover, the rapid losses of nucleobases to pond seepage during wet periods, and to UV photodissociation during dry periods, mean that the synthesis of nucleotides and their polymerization into RNA occurred in just one to a few wet–dry cycles. Under these conditions, RNA polymers likely appeared before 4.17 billion years ago.