The undreamt-of breakthrough of molecular biology has made the problem of the origin of life a greater riddle than it was before: we have acquired new and deeper problems. — Karl R. Popper, 1974 (.2)
Nobody understands the origin of life. If they say they do, they are probably trying to fool you. — Ken Nealson, 2002 (.5)
We emerge inevitably or by luck from the chipping of DNA by cosmic rays, chemical currents in space, the bubbling of volcanic mud. — Dennis Overbye, 2004 (.6)
The RNA World And Other Origin-of-Life Theories | What'sNEWVirtually all biologists now agree that bacterial cells cannot form from nonliving chemicals in one step. If life arises from nonliving chemicals, there must be intermediate forms, "precellular life." Of the various theories of precellular life, the most popular contender today is "the RNA world."
RNA has the ability to act as both genes and enzymes. This property could offer a way around the "chicken-and-egg" problem. (Genes require enzymes; enzymes require genes.) Furthermore, RNA can be transcribed into DNA, in reverse of the normal process of transcription. These facts are reasons to consider that the RNA world could be the original pathway to cells. James Watson enthusiastically praises Sir Francis Crick for having suggested this possibility (1):
The time had come to ask how the DNA→ RNA→ protein flow of information had ever got started. Here, Francis was again far ahead of his time. In 1968 he argued that RNA must have been the first genetic molecule, further suggesting that RNA, besides acting as a template, might also act as an enzyme and, in so doing, catalyze its own self-replication.
It was prescient of Crick to guess that RNA could act as an enzyme, because that was not known for sure until it was proven in the 1980s by Nobel Prize-winning researcher Thomas R. Cech (2) and others. The discovery of RNA enzymes launched a round of new theorizing that is still under way. The term "RNA world" was first used in a 1986 article by Harvard molecular biologist Walter Gilbert (3):
The first stage of evolution proceeds, then, by RNA molecules performing the catalytic activities necessary to assemble themselves from a nucleotide soup. The RNA molecules evolve in self-replicating patterns, using recombination and mutation to explore new niches. ... they then develop an entire range of enzymic activities. At the next stage, RNA molecules began to synthesize proteins, first by developing RNA adaptor molecules that can bind activated amino acids and then by arranging them according to an RNA template using other RNA molecules such as the RNA core of the ribosome. This process would make the first proteins, which would simply be better enzymes than their RNA counterparts. ... These protein enzymes are ... built up of mini-elements of structure.
There is a lot to learn about RNA, and research like this is how we learn it. But these and other similar findings arrived at in highly orchestrated experiments that start with biologically produced RNA are very far from proving that the RNA world is the pathway between nonlife and life. In nature, far from the sterilized laboratory, uncontaminated RNA strands of any size would be unlikely to form in the first place. "... The direct synthesis of ... nucleotides from prebiotic precursors in reasonable yield and unaccompanied by larger amounts of unrelated molecules could not be achieved by presently known chemical reactions" (5).
At the Salk Institute for Biological Studies, in 1994, Leslie Orgel observes, "Because synthesizing nucleotides and achieving replication of RNA under plausible prebiotic conditions have proved so challenging, chemists are increasingly considering the possibility that RNA was not the first self replicating molecule..." (9).
Apparently NASA has lost enthusiasm for the RNA world as well. In the Final Report issued after the "Astrobiology Workshop" held September 9-11, 1996 at Ames Research Center, California, we read (10),
It has been postulated that there was a time in protobiological evolution when RNA played a dual role as both genetic material and a catalytic molecule ("the RNA world"). However, this appealing concept encounters significant difficulties. RNA is chemically fragile and difficult to synthesize abiotically. The known range of its catalytic activities is rather narrow, and the origin of an RNA synthetic apparatus is unclear.
In spite of the intense level of work on the RNA world in the last decade, there is no consensus theory for precellular life. There are many theories. Here are some of the others —
The Time Problem
To go from a bacterium to people is less of a step than to go from a mixture of amino acids to a bacterium. — Lynn Margulis (21.5)
The only premise that all of the precellular theories share is that it would be an extremely long time before the first bacterial cells evolved. If precellular life somehow got going, it could then conceivably begin to crank out, by some precellular process, random strings of nucleotides and amino acids, trying to luck into a gene or a protein with advantages which would lead to bacterial life. There is no evidence in life today of anything that produces huge quantities of new, random strings of nucleotides or amino acids, some of which are advantageous. But if precellular life did that, it would need lots of time to create any useful genes or proteins. How long would it need? After making some helpful assumptions we can get the ratio of actual, useful proteins to all possible random proteins up to something like one in 10^500 (ten to the 500th power). So it would take, barring incredible luck, something like 10^500 trials to probably find one. Imagine that every cubic quarter-inch of ocean in the world contains ten billion precellular ribosomes. Imagine that each ribosome produces proteins at ten trials per minute (about the speed that a working ribosome in a bacterial cell manufactures proteins). Even then, it would take about 10^450 years to probably make one useful protein. But Earth was formed only about 4.6 x 10^9 years ago. The amount of time available for this hypothetical protein creation process was maybe a few hundred million or ~10^8 years. And now, to make a cell, we need not just one protein, but a minimum of several hundred.
So even if we allow precellular life, there is a problem getting from there to proteins, genes and cells. The random production of proteins does not succeed as an explanation. Other intermediate, unspecified stages must be imagined. We could call these stages post-precellular life. By whatever means, life's evolution through these stages would have to be time-consuming.
One advocate of the RNA world, Gerald Joyce, allows 400 million years for "The Rise and Fall of the RNA World" (22):
...At some point RNA organisms began to dabble in the use of short peptides, leading eventually to the development of protein synthesis. Other "experiments" led to the discovery of DNA, which provided a more stable repository for genetic information. By 3.6 to 3.8 billion years ago all of these events had come to pass; the RNA world had fallen and the DNA/protein world had risen in its place.
But other researchers see evidence for prokaryotic cells in the first 100 million years, maybe even immediately. "...Actual cells have been found in the earth's oldest unmetamorphosed sediments...," says Gould in Wonderful Life (23). Bada says that cyanobacteria may have emerged only ten million years after the first precellular life (24). In November, 1996, S. J. Mojzsis of the Scripps institution of Oceanography and others reported isotopic evidence that cellular metabolism was under way before 3.8 billion years ago (25). Even before the research by Mojzsis et al., Francis Crick was worried by the time problem. "...The real fossil record suggests that our present form of protein based life was already in existence 3.6 billion years ago.... This leaves an astonishingly short time to get life started" (26). Another researcher, Peter B. Moore, says this about the time problem (27):
Of one thing we can be certain: The RNA world—if it ever existed—was short-lived. The earth came into existence about 4.5 x 10^9 years ago, and fossil evidence suggests that cellular organisms resembling modern bacteria existed by 3.6 x 10^9 years before the present.... There are even hints that those early organisms engaged in photosynthesis, which is likely to have been a protein-dependent process then, as now. Thus it appears likely that organisms with sophisticated, protein based metabolisms existed only 0.9 x 10^9 years after the planet's birth.
SummaryIt goes without saying that the emergence of this RNA world and the transition to a DNA world imply an impressive number of stages, each more improbable than the previous one — François Jacob, 1997 (28)
We said that research in the RNA world is a medium-sized industry. This research has demonstrated how exceedingly difficult it would be for living cells to originate by chance from nonliving matter in the time available on Earth. That demonstration is a valuable contribution to science. Additional research will be valuable as well. But to keep insisting that life can spontaneously emerge from nonliving chemicals in the face of the newly comprehended difficulties is puzzling. It is reminiscent of the persistent efforts of medieval alchemists to turn lead into gold.
There is another scientific explanation for the origin of life on Earth. It is that whole cells arrived here from space. (Life "in the first place" is a separate issue, dealt with elsewhere on this website.)
What'sNEWIf life pops up readily in Earth-like conditions, surely it should have started many times right here on Earth — Paul Davies, 2011
Jonathan T. Sczepanski and Gerald F. Joyce, "A cross-chiral RNA polymerase ribozyme" [html], doi:10.1038/nature13900, p 440-442 v 515, Nature, 20 Nov (online 29 Oct) 2014; and commentary:
Carl Zimmer, "On the Origin of Life on Earth" [link], doi:10.1126/science.323.5911.198, p 198-199 v 323, Science, 9 Jan 2009.
23 Dec 2008: Maybe heat-loving prokaryotes are not the oldest form of life.
21 Dec 2008: How ancient organic molecules came together to form the basis of life?
Could life have started in a lump of ice?, Physorg.com, via European Science Foundation, 5 Nov 2008.
20 Oct 2008: Residue from one of Stanley Miller's experiments.... Could These Protocells Tell Us About Earth's Earliest Cells?, Scientific Blogging, 5 Jun 2008.
11 Oct 2008: A short video about pseudo-panspermia from The Learning Channel is online. Martin A. Nowak and Hisashi Ohtsuki, "Prevolutionary dynamics and the origin of evolution" [abstract], doi:10.1073/pnas.0806714105, p 14924-14927 v 105, Proc. Natl. Acad. Sci. USA, 30 Sep (online 12 Sep) 2008. "In the present theory ...we encounter natural selection before replication."
Scientists develop new method to investigate origin of life, Pennsylvania State University, 2 Sep 2008.
Diamonds May Have Jump-Started Life on Earth, by Robert Roy Britt, LiveScience, 26 Jul 2008.
David W. Deamer, "Origins of life: How leaky were primitive cells?" [html], doi:10.1038/454037a, p 37-38 v 454, Nature, 3 Jul 2008. "...At some point in the pathway to the first cellular life, such a system must have arisen spontaneously." We question this assumption.
21 Jun 2008: Panspermia is considered in depth....
Meteorites Delivered the "Seeds" of Earth's Left-hand Life, Newswise.com, 6 Apr 2008.
J. Michael McBride and John C. Tully, "Did life grind to a start?" [link], doi:10.1038/452161a, p 161-162 v 452, Nature, 13 Mar 2008.
Seafloor Chemistry: Life's building blocks made inorganically, by Sid Perkins, Science News, 2 Feb 2008.
Douglas Fox, "Did Life Begin in Ice?" [link], p 52-58, Discover, Feb 2008.
15 Jan 2008: Did life begin on a radioactive beach?
New hypothesis for origin of life proposed, re: Helen Hansma, University of California, Santa Barbara, posted on Physorg.com, 4 Dec 2007. "Life may have begun in the protected spaces inside of layers of the mineral mica, in ancient oceans, according to a new hypothesis."
Philipp Baaske et al., "Extreme accumulation of nucleotides in simulated hydrothermal pore systems" [abstract], 10.1073/pnas.0609592104, p 9346-9351; and Eugene V. Koonin's commentary [extract], p 9105-9106, v 104, Proc. Natl. Acad. Sci. USA, 29 May 2007. "...Interlinked mineral pores in a thermal gradient provide a compelling high-concentration starting point for the molecular evolution of life."
Tiny DNA Molecules Show Liquid Crystal Phases, Pointing Up New Scenario For First Life On Earth, the University of Colorado at Boulder, 22 Nov 2007.
Jeremy Pearce, "Leslie Orgel, Biochemist Who Studied Origins of Life, Dies at 80" [text], The New York Times, 5 Nov 2007.
Salk Institute's Leslie Orgel Dies at 80 years old, on October 27; by Heather Chambers, San Diego Business Journal, 31 Oct 2007.
How Did Chemical Constituents Essential To Life Arise On Primitive Earth?, by Philip Lee Williams, University of Georgia News Service, and on ScienceDaily.com, 31 Oct 2007.
Jerry Chancellor alerts us that inorganic dust may make helices under the right conditions in space, 22 Aug 2007.
20 Aug 2007: Comets are much more likely than Earth to have hosted the origin of life....
Eric D. Schneider and Dorion Sagan, Into the Cool: Energy Flow Thermodynamics and Life, The University of Chicago Press, 2005, p 163: Here we argue that a thermodynamically forced protometabolism, capable of making homeostatic-like dissipative structures that enjoyed a primitive reproduction, must have preceded precise replication.
Dale Caruso replies about Francis Crick's theory of panspermia, 9 Aug 2007.
29 Jul 2007: The Limits of Organic Life in Planetary Systems
Rainer Glaser et al., "Adenine Synthesis in Interstellar Space: Mechanisms of Prebiotic Pyrimidine-Ring Formation of Monocyclic HCN-Pentamers" [abstract], 10.1089/ast.2006.0112, p 455-470 v 7, Astrobiology, Jul 2007.
Justin A. Bradford and Ken A. Dill, "Stochastic innovation as a mechanism by which catalysts might self-assemble into chemical reaction networks" [abstract], doi:10.1073/pnas.0703522104, p 10098-10103 v 104, Proc. Natl. Acad. Sci. USA, 12 Jun 2007.
Scientists propose the kind of chemistry that led to life, Physorg.com, 8 Jun 2007. "...Either a primitive kind of metabolism or an RNA-like duplicating machinery must have set the stage.... But what preceded these pre-life steps?"
29 May 2007: A Simpler Origin for Life is what Robert Shapiro claims to explain in Scientific American.
Stanley L. Miller dies, by Kelly Rae Chi, The Scientist, 24 May 2007.
RNA enzyme structure offers a glimpse into the origins of life, Physorg.com, 15 Mar 2007.
4 Apr 2007: How did life on Earth originate?
Programming the Universe: A Quantum Computer Scientist Takes On the Cosmos, by Seth Lloyd, Alfred A. Knopf/Jonathan Cape: 2006; reviewed by Artur Ekert, "The Universe's quantum monkeys" [text], 10.1038/445366a, p 366-367 v 445, Nature, 25 Jan 2007.
9 Nov 2006: Harvard's Origins of Life program held its inaugural symposium, 8 Nov 2006.
On the Origins of Life, by David Berlinski, first published in Commentary, 14 Feb 2006. "Why should self-replicating RNA molecules have been common 3.6 billion years ago when they are impossible to discern under laboratory conditions today?"
Arthur L. Weber and Sandra Pizzarello, "The peptide-catalyzed stereospecific synthesis of tetroses: A possible model for prebiotic molecular evolution" [abstract], 10.1073/pnas.0602320103, Proc. Natl. Acad. Sci. USA, online 11 Aug 2006. "Because peptides might have formed readily on the early Earth, it is possible that their catalytic contribution was relevant in the prebiotic processes that preceded the onset of life."
Kalin Vetsigian, Carl Woese and Nigel Goldenfeld, "Collective evolution and the genetic code" [abstract], 10.1073/pnas.0603780103, Proc. Natl. Acad. Sci. USA, online 3 Jul 2006. "...a variety of collective, but non-Darwinian, mechanisms... generically lead to refinement and selection of innovation-sharing protocols, such as the genetic code.... before the emergence of vertical descent."
17 May 2006: A stupendously improbable accident is Robert Shapiro's characterization of the RNA World.
Methane-Belching Bugs Inspire a New Theory of the Origin of Life on Earth, Penn State; also posted by Physorg.com, 12 May 2006. Original article by James G. Ferry and Christopher H. House, "The Stepwise Evolution of Early Life Driven by Energy Conservation" [abstract], 10.1093/molbev/msk014, p 1286-1292 v 23, Molecular Biology and Evolution, Jun (online 31 Mar) 2006.
'Accelerated Evolution' Converts RNA Enzyme to DNA Enzyme In Vitro, by Eric Sauter, News & Views, The Scripps Research Institute, 27 Mar 2006.
13 Feb 2006: Origin-of-life theory comes up short, according to David Deamer.
S. D. Senanayake and H. Idriss, "Photocatalysis and the origin of life: Synthesis of nucleoside bases from formamide on TiO2(001) single surfaces" [abstract], 10.1073/pnas.0505768103, Proc. Natl. Acad. Sci. USA, online 19 Jan 2005. "...Some minerals in the form of oxide semiconductors are active materials for making high-molecular-weight organic molecules that may have acted as precursors for biological compounds...."
John Whitfield, "Base Invaders" [link], doi:10.1038/439130a, p 130-131 v 439, Nature, 12 Jan 2006. "Could viruses have invented DNA as a way to sneak into cells?"
20 Dec 2005: Life as We Do Not Know It, by Peter Ward.
Ronald Breaker, "Journal Club," p 399 v 438, Nature, 24 Nov 2005. "As a supporter of [The RNA World] theory.... [I] suspect that ancient organisms had a bumpy evolutionary ride until proteins emerged...."
NSF Grant Awarded to SFI to Study How Life Emerged on Earth, Santa Fe Institute, 18 Oct 2005.
Paul Davies, "A quantum recipe for life" [text], doi:10.1038/437819a, p 819 v 437, Nature, 6 Oct 2005.
Illinois Researchers To Play Key Roles In Study Of Emergence Of Life (popups), TerraDaily, 29 Sep 2005.
22 Sep 2005: Genesis, a new book about the origin of life, ignores the software problem.
Ádám Kun, Mauro Santos and Eörs Szathmáry, "Real ribozymes suggest a relaxed error threshold" [abstract], doi:10.1038/ng1621, p 1008-1011 v 37, Nature Genetics, online 28 Aug 2005.
Scientists ...point to 'hot soup' at the origin of life, University of Bath, 2 Aug 2005.
Alexander V. Vlassov et al., "The RNA World on Ice: A New Scenario for the Emergence of RNA Information" [abstract], doi:10.1007/s00239-004-0362-7, Journal of Molecular Evolution, online 21 Jul 2005.
22 Apr 2005: Jeffrey Bada is optimistic about the origin-of-life problem.
pdf: How Do Biological Systems Originate?, by Norman R. Pace, abstract of lecture at NAI Conference, 12 Apr 2005.
William R. Taylor, "Does changing the direction of replication make RNA life viable?" doi:10.1038/434705a, p 705 v 434, Nature, 7 Apr 2005.
Eörs Szathmáry, "In search of the simplest cell" [text], doi:10.1038/433469a, p 469-470 v 433, Nature, 3 Feb 2005. "Lipid world"?
Antonio Lazcano, "An Answer in Search of a Question" [review of William Day's How Life Began], p 469-471 v 4, Astrobiology, 2004. Day endorses Wächtershäuser, but Lazcano doubts that life can begin without genetic material.
...Volcanic Gas May Have Played a Significant Role in the Origins of Life on Earth, by Jason Socrates Bardi, Scripps Research Institute, 11 Oct 2004.
28 Sep 2004: Nova explains the origin of life.
Battle of the Bubbles May Have Sparked Evolution, Howard Hughes Medical Institute, 3 Sep 2004.
Man who helped unlock DNA dies (Francis Crick, age 88), BBC News, 29 July 2004.
Carl Zimmer, "What Came Before DNA?" [intro], p 34-41 v 25 n 6 Discover, June 2004. "Scientists may soon reveal how life began on Earth — by creating a primordial organism in the lab."
Molecular midwives hold clues to the origin of life, Georgia Institute of Technology Research News, 31 Mar 2004. "Small, simple molecules acted as templates for the production of the first RNA-like molecules."
13 Feb 2004: Nonliving to living?
A. Ricardo, M. A. Carrigan, A. N. Olcott and S. A. Benner, "Borate Minerals Stabilize Ribose" [text], p 196 v 303 Science, 9 Jan 2004. See also: UF study suggests life on Earth sprang from borax minerals, EurekAlert!, 8 Jan 2004.
Jack Lucentini, "Darkness Before the Dawn - of Biology" [text], p 28 v 17 The Scientist, 1 Dec 2003. "...First cells would have had to divide or bud and, at the same time, pass on a code for growth and maintenance...".
2003, Oct 6: Peter Ward wonders: If life is so easy to make....
Biology's Theme Park: RNA World, by David Bartel, Astrobiology Magazine, 2 Sep 2003. "Life was a garbage bag."
New clues to identity of first genetic molecule, NewScientist.com, 27 July 2003. "TNA could be a long-lost precursor to RNA."
Origin of Life, Gordon Research Conference, Bates College, Maine, 13-18 July 2003.
UV light may have sparked life on Earth, NewScientist.com, 28 May 2003. "...A new mathematical model implies the radiation actually helped select out the molecular seeds of life."
2003, May 8: ...Huygens Probe [with ESA's comments about "primeval soup"].
2003, May 2: Revisiting the Miller Experiment....
2002, Dec 24: Life's Origin, J. William Schopf, ed.
"Binary" Enzyme Created By Scripps Scientists Demonstrates Darwinian Evolution At Its Simplest, ScienceDaily, 19 Dec 2002."It is possible to have a genetic system of molecules capable of undergoing Darwinian evolution with only two distinct subunits."
New theory for origin of life, by John Whitfield, Nature ScienceUpdate, 4 Dec 2002."Mineral cells might have incubated first living things."
2002, August 19: New evolution theory is survival by gene sharing.
2002, July 27: RNA World: the latest
Were the first macromolecules created on a primitive beach?, by Joanna Gibson, John Wiley and Sons, 19 June 2002.
Ponds, not oceans, the cradle of life, by Matt Kaplan, New Scientist, 9 May 2002.
Michael Hagmann, "Günter Wächtershäuser Profile..." [summary], p 2006-2007 v 295 Science, 15 Mar 2002.
Joseph L. Kirschvink and Benjamin P. Weiss, "Mars, Panspermia, and the Origin of Life: Where Did It All Begin?" [html | pdf], v4 n2 Palaeontologia Electronica, Jan 2002.
Cells from Scratch, by Maia Szalavitz, HMSBeagle, 31 August 2001 [Registration required].
Study Offers Insights into Evolutionary Origins of Life; Artificial Enzyme Able to Synthesize RNA, Whitehead Institute, 17 May 2001. "We will never be able to prove the existence of the RNA world because we can't go back in time—but we can examine the basic properties of RNA and see if these are compatible within the RNA world scenario."
Reflections From a Warm Little Pond, by David Pacchioli, SpaceDaily.com, 10 May 2001. Lightly reviews the development of RNA World theory.
Robert M. Hazen et al., "Selective adsoption of L-and D-amino acids on calcite: Implications for biochemical homochirality" [abstract], PNAS, 1 May 2001. "A plausible geochemical mechanism for the production of homochiral polypeptides on the prebiotic Earth."
Robert M. Hazen, "Life's Rocky Start," p 76-85 v 284 n 4 Scientific American, April 2001. A major plug for minerals as scaffolding for the first genetic material. No mention of a source for the instructions in the genetic material.
Found in sequence space, by John Whitfield, Nature Science Update, 5 April 2001.
TNA World, NASA Astrobiology Institute, 12 March 2001.
2001, January 29: "NASA Scientists Find Clues That Life Began in Deep Space."
2000, November 17: The TNA World.
Günter Wächtershäuser, "Life as We Don't Know It" [summary], p 1307 v 289 Science, 25 August 2000. The "iron-sulfer world" gets a new plug.
2000, August 8: A reply from Stephen Sowerby elaborates on a mineral template mechanism.
Did droplets high in the atmosphere give birth to the first living cells?, by Joanna Marchant, New Scientist, 15 July 2000.
Life, but not as we know it, by Henry Gee, Nature Science Update, 27 June 2000.
Ancient Organisms Born in Undersea Inferno A 'medieval version of hell' as cradle of life, San Francisco Chronicle, 8 June 2000.
Scientists At The Weizmann Institute Propose A New Theory To The Mystery Of The Origin Of Life, Weizmann Institute of Science, 5 June 2000.
2000, May 22: An online review of origin-of-life theories...
Darwin's Soup And The Origins of Life — review of The Spark of Life by Christopher Wills and Jeffrey Bada. Previous theories "circle maddeningly around the problem without ever quite coming to grips with it." SpaceDaily, 3 May 2000.
New calculations show life's origins possible in volcanic gases — another new theory, EurekAlert!, 27 March 2000.
The Origin of Life at britannica.com. One of the four listed hypotheses is, "Life is coeternal with matter and has no beginning; life arrived on the Earth at the time of the origin of the earth or shortly thereafter."
1999, December 23: Lord Kelvin's address to British scientists, in 1871.
Stephen J. Freeland, Robin D. Knight and Laura F. Landweber, "Do Proteins Predate DNA?" p 690-692 v 286 Science, 22 October 1999.
"How close are scientists to knowing the origin of life on earth? When, if ever, will we be able to explain the origin of life in purely scientific terms?" [blog link], ScientificAmerican.com, 21 October 1999.
Examining life's building blocks, by Alan Boyle, MSNBC, 30 July 1999. "Astronomers and biochemists have found new evidence to back up their assorted scenarios for the origin of life on Earth."
1999, May 18: Biochemist Robert Shapiro advocates a "Life Principle" for the origin of life from nonlife.
1999, April 24: Cytosine is unlikely to have been available for the origin of life.
Nicholas Wade, "Inside the Cell, Experts See Life's Origin" The New York Times, 6 April 1999. Commenting on the new edition of The RNA World from Cold Spring Harbor Laboratory Press, Wade writes, "Much has been learned about RNA since the book's first edition in 1993, yet the new knowledge, rather than bolstering the theory of RNA's leading role, seems to accentuate its difficulties."
1999, February 19: NASA says astrobiologists find clues to origin of life.
1998, July 28: Carl R. Woese says lateral gene transfer is more important than vertical inheritance at first. And he discards the notion of a "last common ancestor," which serves as the North Star for neo-Darwinism.
References.2. Karl R. Popper, "Reduction and the Essential Incompleteness of All Science," p 259-284, Studies in the Philosophy of Biology, Francisco Jose Ayala and Theodosius Dobzhansky, eds. University of California Press, 1974. p 271.
.5. Robert Roy Britt, "The Search for the Scum of the Universe," Space.com, 21 May 2002.
.6. Dennis Overbye, "Adventure or Inquiry? Two Visions of Cosmic Destiny" [text], The New York Times, 3 Feb 2004.
1. James D. Watson, "Prologue: Early Speculations and Facts about RNA Templates," p xv-xxiii, The RNA World, R.F. Gesteland and J.F. Atkins, eds. Cold Spring Harbor Laboratory Press, 1993. p xxiii.
2. Thomas R. Cech, "A model for the RNA-catalyzed replication of RNA" [abstract], p 4360-4363 v 83, Proc. Nat. Acad. Sci., USA, 1986.
3. Walter Gilbert, "The RNA world" [link], p 618 v 319, Nature, 1986.
4. Eric H. Eckland, Jack W. Szostak and David P. Bartel, "Structurally Complex and Highly Active RNA Ligases Derived from Random RNA Sequences" [abstract], doi:10.1126/science.7618102, p 364-370 v 269, Science, 21 July 1995.
5. Gerald F. Joyce, and Leslie E. Orgel, "Prospects for Understanding the Origin of the RNA World," p 1-25, The RNA World, R.F. Gesteland and J.F. Atkins, eds. Cold Spring Harbor Laboratory Press, 1993.
6. F. H. C. Crick and L. E. Orgel, "Directed Panspermia" [public access pdf], p 341-346 v 19, Icarus, 1973.
7. Francis Crick, Life Itself, Simon and Schuster, 1981.
8. Francis Crick, "Foreword," p xi-xiv, The RNA World, R.F. Gesteland and J.F. Atkins, eds. Cold Spring Harbor Laboratory Press, 1993. p xiii.
10. D. DeVincenzi, ed. "Final Report," Astrobiology Workshop at NASA Ames Research Center. December 1996.
11. Periannan Senapathy, Independent Birth of Organisms, Madison, WI. Genome Press, 1994.
11.5. Manfred Eigen, Steps Towards Life: A Perspective on Evolution (German edition, 1987), Oxford University Press, 1992. p 31.
12. Freeman J. Dyson, Origins of Life, Cambridge University Press, 1985.
13. A. G. Cairns-Smith, Seven Clues to the Origin of Life, Cambridge University Press, 1985.
14. Günter von Kiedrowski, "Primordial soup or crêpes?" p 20-21 v 381, Nature, 2 May 1996.
14.5. Joseph V. Smith, "Biochemical evolution. I. Polymerization on internal, organophilic silica surfaces of dealuminated zeolites and feldspars" [abstract], p 3370-3375 v 95, Proc. Nat. Acad. Sci. USA, 31 Mar 1998. Also see How did life begin? Biochemical evolution on mineral surfaces, The University of Chicago News.
15. Harold J. Morowitz, Beginnings of Cellular Life: Metabolism Recapitulates Biogenesis, Yale University Press, 1992.
16. Carl Zimmer, "First Cell," p 70-78 v 16 n 11, Discover.
17. Harold J.Morowitz, Bettina Heinz and David W. Deamer, "The Chemical Logic of a Minimum Protocell," p 281-287 v 18, Origins of Life and Evolution of the Biosphere, 1988.
18. Jeffrey L. Bada, "Cold Start," p 21-25, The Sciences May/June 1995.
19. Jeffrey L. Bada, "The Organic Chemistry of the Early Earth," presented to the American Association for the Advancement of Science, February 20, 1994.
19.5. Claudia Huber and Günter Wächtershäuser, "Peptides by Activation of Amino Acids with CO on (Ni,Fe)S Surfaces: Implications for the Origin of Life," p 670-672 v 281, Science, 31 July 1998. Also see commentary by Gretchen Vogel, "A Sulfurous Start for Protein Synthesis?" p 627.
19.6. Nicholas Wade, "Experiment Supports Theory That Life Began in Volcanic Environment," The New York Times, 31 July 1998.
19.7. Kenneth Chang, "Cooking Up Life's Origins," ABCNEWS.com, 30 July 1998.
19.8. Thomas Gold, "The Deep, Hot Biosphere", July 1992.
20. Stuart Kauffman, At Home in the Universe, Oxford University Press, 1995. p 45.
21. Christof Böhler, Peter E. Nielsen and Leslie E. Orgel, "Template switching between PNA and RNA oligonucleotides," p 578-581 v 376, Nature, 17 August 1995.
21.5. Lynn Margulis, interviewed in The End of Science, by John Horgan. Addison-Wesley Publishing Company, Inc., 1996. p 140-141.
22. Gerald F. Joyce, "The Rise and Fall of the RNA World," p 339-407 v 3, The New Biologist, 1991.
23. Stephen Jay Gould, Wonderful Life: The Burgess Shale and the Nature of History, W.W. Norton and Company, 1989. p 58.
24. Jeffrey L. Bada, "Talk of the Nation: Science Friday." National Public Radio. 15 September 1995.
25. S. J. Mojzsis, G. Arrhenius, K.D. McKeegan, T.M. Harrison, A.P. Nutman and R.L. Friend, "Evidence of life on earth before 3,800 million years ago," p 55-59 v 384, Nature, 7 November, 1996. See also comentary by Henry Gee, and additional discussion and references at Life Before 3850 Million Years Ago?, this website, first posted November 7, 1996.
26. Francis Crick, "Foreword," p xi-xiv, The RNA World, R.F. Gesteland and J.F. Atkins, eds. Cold Spring Harbor Laboratory Press, 1993. p xiv.
27. Peter B. Moore, "Ribosomes and the RNA World," p 119-135, The RNA World, R.F. Gesteland and J.F. Atkins, eds. Cold Spring Harbor Laboratory Press, 1993. p 131.
28. François Jacob, Of Flies Mice and Men (translated by Giselle Weiss), Harvard University Press, 1998. p 21.
Related ReadingBalter, Michael. "Did Life Begin in Hot Water?" p 31 v 280, Science, 3 April 1998.
Baserga, Susan J. and Joan A. Steitz. "The Diverse World of Small Ribonucleoproteins," p 359-381, The RNA World, R.F. Gesteland and J.F. Atkins, eds. Cold Spring Harbor Laboratory Press, 1993.
Benner, Steven A.; Andrew D. Ellington and Andreas Tauer. "Modern metabolism as a palimpsest of the RNA world," p 7054-7058, Proceedings of the National Academy of Sciences, USA v 86. September 1989.
Brack, André (ed.), The Molecular Origins of Life: Assembling Peices of the Puzzle, Cambridge University Press, 1998.
Cech, Thomas R. "RNA as an Enzyme," Scientific American, November, 1986.
Cech, Thomas R. "Structure and Mechanism of the Large Catalytic RNAs: Group I and Group II Introns and Ribonuclease P," p 239-269, The RNA World, R.F. Gesteland and J.F. Atkins, eds. Cold Spring Harbor Laboratory Press, 1993.
Cohen, Jon. "Novel Center Seeks to Add Spark to Origins of Life," p 1925-1926 v 270, Science, 22 December 1995.
Crick, Francis. "Split genes and RNA Splicing," p 264-271 v 204, Science, 20 April 1979.
Deamer, David W. and Gail R. Fleischaker, Origins of Life: The Central Concepts, Jones and Bartlett Publishers, 1994.
de Duve, Christian. "The chemical origin of life," p 391-400, Astronomical and Biochemical Origins and the Search for Life in the Universe, Cristiano Batalli Cosmovici, Stuart Bowyer and Dan Werthimer, eds. Editrice Compositori, 1997.
Doolittle, Russell F. "Probability and the Origin of Life," p 85-97, Scientists Confront Creationism, Laurie R. Godfrey, ed. W. W. Norton and Company, 1983.
Ellington, Andrew D. "Experimental Testing of Theories of an Early RNA World," p 646-664 v 224, Methods in Enzymology, 1993.
Ferris, James P. "Prebiotic Synthesis: Problems and Challenges," p 29-35, Cold Spring Harbor Symposia on Quantitative Biology, Volume LII: Evolution of Catalytic Function, Cold Spring Harbor Laboratory, 1987.
Ferris, James P. "Life at the Margins," p 659 v 373, Nature, 23 February 1995.
Ferris, James P.; Aubrey R. Hill, Jr.; Rihe Liu and Leslie Orgel. "Synthesis of long prebiotic oligomers on mineral surfaces," p 59-61 v 381, Nature, 2 May 1996.
Galtier, Nicolas; Nicolas Tourasse and Manolo Gouy. "A Nonhyperthermophylic Common Ancestor to Extant Life Forms," p 220-221; and commentary by Gretchen Vogel, "RNA Study Suggests Cool Cradle of Life," p 155-156 v 283, Science, 8 January 1999.
Horgan, John. "Life, Life Everywhere," Scientific American, November 1996.
Hotz, Robert Lee. "Probing the Chemistry of Creation," Los Angeles Times, 15 May 1997.
Joyce, G. F. "Nonenzymatic Template-directed Synthesis of Informational Macromolecules," p 41-51, Cold Spring Harbor Symposia on Quantitative Biology, Volume LII: Evolution of Catalytic Function, Cold Spring Harbor Laboratory, 1987.
Keefe, Anthony D.; Gerald L. Newton and Stanley L. Miller. "A possible prebiotic synthesis of pantetheine, a precursor to coenzyme A," p 683-685 v 373, Nature, 23 February 1995.
Keller, M.; E. Blöchl; G. Wächtershäuser and K. O. Stetter. "Formation of amide bonds without a condensation agent and implications for origin of life," p 836-838 v 368, Nature, 28 April 1994.
Lazcano, Antonio and Stanley L. Miller. "How Long Did It Take for Life to Begin and Evolve to Cyanobacteria?" p 546-554 v 39, Journal of Molecular Evolution, 1994.
Lee, David H., Juan R. Granja, Jose A. Martizez, Kay Severin and M. Reza Ghardi. "A self-replicating peptide," p 525-528 v 382, Nature, 8 August 1996.
Lewis, Ricki. "Primordial Soup Researchers Gather at Watering Hole," p 1034-1035 v 277, Science, 22 August 1997.
Luisi, Pier Luigi. "Self-reproduction of chemical structures and the question of the transition to life," p 461-468, Astronomical and Biochemical Origins and the Search for Life in the Universe, Cristiano Batalli Cosmovici, Stuart Bowyer and Dan Werthimer, eds. Editrice Compositori, 1997.
Maddox, John. "Origin of life by careful reading," p 409 v 367, Nature, 3 February 1994.
Maddox, John. "RNA in primaeval genetics," p 29-30 v 372, Nature, 3 November 1994.
Maynard Smith, John and Eörs Szathmáry, The Major Transitions in Evolution, W. H. Freeman and Company, Limited, 1995.
Oparin, A. I., The Origin of Life On Earth, 3rd edition, Academic Press Inc., Publishers, 1957.
Orgel, Leslie E. "Evolution of the Genetic Apparatus: A Review," p 9-16, Cold Spring Harbor Symposia on Quantitative Biology, Volume LII: Evolution of Catalytic Function, Cold Spring Harbor Laboratory, 1987.
Orgel, Leslie E., The Origins of Life: Molecules and Natural Selection, John Wiley and Sons, Inc., 1973.
Orò, J.; T. Mills and A. Lazcano. "Comets and the Formation of Biochemical Compounds on the Primitive Earth - A Review," p 267 - 277 v 21 n 5-6, Origins of Life and Evolution of the Biosphere, 1991–1992.
Pennisi, Elizabeth. "Seeking Life's Bare (Genetic) Necessities," p 1098-1099 v 272, Science, 24 May 1996.
Piccirilli, Joseph A. "RNA seeks its maker," p 548-549 v 376, Nature, 17 August 1995.
Poole, Anthony M.; Daniel C Jeffares and David Penny. "The Path from the RNA World," p 1-17 v 46, Journal of Molecular Evolution, 1998.
Rizzotti, Martino. "Did a precellular RNA world ever exist?" p 477-482, Astronomical and Biochemical Origins and the Search for Life in the Universe, Cristiano Batalli Cosmovici, Stuart Bowyer and Dan Werthimer, eds. Editrice Compositori, 1997.
Robertson, Hugh D. "Life Before DNA," p 1479-1480 v 264, Science, 3 June 1994.
Robertson, Hugh D. "How Did Replicating and Coding RNAs First Get Together?" p 66-67 v 274, Science, 4 October 1996.
Robertson, Michael P. and Stanley L. Miller. "Prebiotic Synthesis of 5-Substituted Uracils: A Bridge Between the RNA World and the DNA-Protein World," p 702-705 v 226, Science, 5 May 1995.
Rose, George D. "No Assembly Required," p 26-31 v 36 n 1, The Sciences, January / February 1996.
Schidlowski, M. "The Beginnings of Life on Earth: Evidence from the Geological Record," p 389-414, The Chemistry of Life's Origins, J.M. Greenberg, C.X. Mendoza-G=mez and V. Pirronello, eds. Kluwer Academic Publishers, 1993.
Schwemmler, Werner, Reconstruction of Cell Evolution: A Periodic System, CRC Press, 1984. (Original German edition, 1979).
Schwartz, A.W. "Biology and Theory: RNA and the Origin of Life," p 323-344, The Chemistry of Life's Origins, J.M. Greenberg, C.X. Mendoza-G=mez and V. Pirronello, eds. Kluwer Academic Publishers, 1993.
Senapathy, Periannan. "Introns and the Origin of Protein-Coding Genes," p 1366-1367 v 268, Science, 2 June 1995.
Stein, Wilfred and Francisco J. Varela, eds., Thinking About Biology, Addison-Wesley Publishing Company, 1993.
Wade, Nicholas. "Amateur Shakes Up Ideas on Recipe for Life," p B9, B12, The New York Times, 22 April 1997.
Waldrop, M. Mitchell. "Did Life Really Start Out in an RNA World?" p 1248-1249 v 246, Science, 8 December 1989.
Wills, Peter. "Turning the Corner on the Search for the Origin of Life," p 14-17 v 12 n 2, SFI Bulletin, Summer 1997.
Woese, Carl R. and Norman R. Pace. "Probing RNA Structure, Function, and History by Comparative Analysis," p 91-117, The RNA World, R.F. Gesteland and J.F. Atkins, eds. Cold Spring Harbor Laboratory Press, 1993.
Wright, Martin C and Gerald F. Joyce. "Continuous in Vitro Evolution of Catalytic Function," p 614-617 v 276, Science, 25 April 1997.
Yang, Jian; Steven Zimmerly; Peter Perlman and Alan M. Lambowitz "Efficient integration of an intron RNA into double-stranded DNA by reverse splicing," p 332-335 v 381, Nature, 23 May 1996.
Yockey, Hubert P., Information theory and molecular biology, Cambridge University Press, 1992.
Zaug, Arthur J. and Thomas R. Cech. "The Intervening Sequence RNA of Tetrahymena Is an Enzyme," p 470-475 v 231, Science, 1986.
Zhang, Biliang and Thomas R. Cech. "Peptide bond formation by in vitro selected ribozymes," p 96-100 v 390, Nature, 6 November 1997.
Related Websites: The RNA WorldThe Origin of Life on Earth by Leslie E. Orgel.
The RNA World at IMB Jena
Scientists Debate RNA's Role At Beginning Of Life On Earth by Ricki Lewis, p 11,14 v 11 n 7, The Scientist, 31 March 1997.
Molecular "Fossils" Of Early Life: Yale Scientists Recreate Molecular "Fossils," Now Extinct, That May Have Existed At The Beginning Of Life, EurekAlert, 5 June 1998.
Related Websites: The origin of life "in the first place"The Origin of Life at Rensselaer Polytechnic Institute
Ames Research Center, Astrobiology Office: NASA's Astrobiology Institute.
Origins: NASA's Origins Program.
The Mystery of Life's Origin: a well-researched 1984 book with a creationist conclusion.
From Primordial Soup to the Prebiotic Beach, an interview with Dr. Stanley L. Miller, October 1996.
Origin of Life Research (Glasgow), yet another origin-of-life theory, from the University of Glasgow.