Origins of Life
Fazale Rana and Hugh Ross
Ch. 1 Questions, Questions -- Always Questions
p 23 Because the origin of complex life so soon is so difficult a problem, Kelvin, Helmholtz and Arrhenius argued vigorously for panspermia. Others argued for a special "life force", a position that was termed neovitalism.
p 24 The Oparin-Haldane Hypothesis in the 1920s was a detailed outline for abiogenesis. It was the foundation for the Miller-Urey experiments in the 1950s.
p 24 The Murchison Meteorite of 1969 had a number of amino acids.
p 25 Sidney Fox in 1970s coaxed amino acids to condense into "proteinoids", but this approach has not yielded much beyond that.
p 25 Paul Davies quote from "The Fifth Miracle" in 1999 concludes that a "huge gulf" remains in the understanding of life's origins.
p 26 Davies "Many investigators feel uneasy about stating in public that the origin of life is a mystery, even though behind closed doors they freely admit that they are baffled. There seems to be two reasons for their unease. First, they feel it opens the door to religious fundamentalists and their god-of-the-gaps pseudoexplanations. Second, they worry that a frank admission of ignorance will undermine funding."
p 26 "Origin-of-life investigators have successfully discovered many plausible chemical routes, from simple compounds to biologically important compounds. Yet for other critical biomolecules no pathways are known - in fact, they may not exist."
p 27 "investigators have discovered that life in its most minimal form requires an astonishing number of proteins that must be spatially and temporally organized within the cell."
Ch. 2 Are There Any Answers?
p 30 Nobel laureate Francis Crick in his book "Life Itself" recognizes that life's origin appears to be "almost a miracle, so many are the conditions which would have had to be satisfied to get it going." Yet Crick rejects consideration of any supernatural basis.
p 30 Davies in The Fifth Miracle concedes "science rejects true miracles ... the starting point of any scientific investigation must be the assumption that life emerged naturally, via a sequence of normal physical processes."
p 30 Niles Eldridge, paleontologist, in "The Triumph of Evolution and the Failure of Creationism" says "We humans can directly experience that material world only through our senses, and there is no way we can experience the supernatural." A number of quotes along this line from Eldridge.
p 32 "Many Christians think that by pointing out the many problems confronting origin-of-life researchers, they have proven the case for biblical creationism. The scientific community finds this negative approach repugnant, and rightfully so. "
p 33 "Models advocating supernatural intervention in nature must be testable and must generate predictions that have the capacity to guide the discovery process."
Ch. 3 Putting Creation to the Test
p 36 Biblical understanding model - historical-grammatical method.
p 37 Davies "The Fifth Miracle" is the appearance of vegetation on the land, with the creation of the universe, light, atmosphere, and dry land as the first four miracles.
p 40 Mainline science chronology: permanent oceans 3.9Gya, continent building 3 Gya, up to 29% by 2.5 Gya and approached equilibrium.
p 42 Recaps the Genesis 1:2 "hovering" scenario with appeal to Deut 32:9-11 and Luke 1:35 for other use of "hovering".
p 43 RTB model predictions.
Ch. 4 The Naturalistic Approach
p 47 A list of the necessary natural pathways for life's development
p 48 Textbook description of life's origin
p 50 Diagram summary of various origin-of-life scenarios currently under consideration.
p 51 Prominent among researchers are deep-sea-vent models and panspermia. Surprising how much prominence is placed on seeding of life from extraterrestrial sources.
p 52 Part of the process involves condensing reations, so this was an interesting discussion of the locations and conditions for such reactions. Mineral surfaces, clays, and other sites have been investigated.
p54 metabolism first vs replicator first scenarios
p55 RNA world
p57 Discussion of LUCA, last universally common ancestor.
p 58 A list of naturalistic predictions.
Ch. 5 An Early or Late Appearance?
p 63 Earth's oldest rocks investigated for early life - Greenland at 3.8Gya, Warrowana Hills of northwestern Australia at 3.3, Barberton Mt Land of eastern South Africa at 3.3.
p 64 Shark Bay, Australia has shoreline boulders that are built up of stromatolites, layers made by matlike colonies of cells that are cyanobacteria - photosynthetic cells that produce oxygen as a byproduct. They date in the neighborhood of 3.5 billion years.
p 69 Isotopic enrichment of carbon-12 is an indicator of life. A more detailed description is in Appendix B.
p 70 isotopic enrichment of nitrogen-14 as well as carbon-12 constitutes geochemical evidence for life.
p 74 Nitrogen-15 and sulfur-32 also serve as markers for biological activity.
p75 Banded iron formations also are an indicator for life. The model is that seasonal upwellings of nutrients boosted the cyanobacteria population, producing more oxygen, which speeded deposition of iron oxide.
p 76 "Prokaryotic microorganisms were firmly entrenched on Earth at 3.7 billion years ago. The record for ancient life may well date beyond this to 3.8+ billion years in age." The extremes around 3.8 are debated, but universal acceptance at 3.5 billion years.
p 77 "An abundance of data indicates that cyanobacteria and other photosynthetic bacteria existed by 3.5 billion years ago." This is amazing because the photosynthetic bacteria are some of the most complex of prokaryotes.
p 79 From J. William Schopf in "The Cradle of Life" "No one had foreseen that the beginning of life occurred so astonishingly early." That captures the essence of this chapter.
Ch. 6 A Slow or Sudden Arrival?
p81 Carl Sagan quote expressing confidence that "The apparatus for the transcription of the genetic code must itself have evolved slowly, through billions of years of evolution."
p 82 The inhospitable early earth and the late heavy bombardment between 3.9 and 3.8 billion years.
p 85 Setting LHB at 3.85 billion years and life at 3.8 billion narrows window for life's emergence to about 50 million years.
p 85 zircons give older ages, back closer to earth's formation at 4.57 billion
p 86 Dating zircons and using oxygen 16 and 18 ratios indicate remeltings between the 4.47 billion year age of moon and the LHB.
p 87 Discussion of model for moon formation by collision.
p 89 Summary of the challenges for origin-of-life in short time span available.
p 91 With quotes like John Hayes, Nature "with breathtaking rapidity" and Ward & Brownlee, Rare Earth "awfully short period of time for first life to evolve" , he includes a number of other statements from Eldridge, Yockey, and earlier Bohr that life is to be just expected.
Ch. 7 Where's the Soup?
p93 List of life's basic ingredients
p94 The phosphorous problem - P necessary for emergence of life, but almost all the phosphate deposits we find came from life
p95 Review of lab experiments and organics found on meteorites - by page 99 concludes that cupboard is bare.
p102 Neither volcanoes or deep-sea vents seem able to supply prebiotics necessary
p104 Carbon and nitrogen isotope ratios fail to support the prebiotic soup picture.
p 104 "The answer is in: There was no prebiotic soup on the menu billions of years ago when life began."
Ch. 8 The Search for Chemical Pathways
p110 After reviewing the Miller-Urey experiment, he summarized why the "bottom-up" scenario is unlikely because of the lack of the pre-biotic soup. "the composition of Earth's primitive atmosphere could not have accommodated the production of prebiotic molecules, and the harsh conditions of hydrothermal vents would have destroyed any prebiotic compounds produced at those locations. The absence of residues from a prebiotic soup in Earth's oldest rocks and the lack of a solution to the oxygen/ultraviolet paradox independently support this conclusion. Many, if not all, the chemical pathways discovered that could conceivably form prebiotic compounds, and hence the prebiotic soup, must be considered irrelevant, given the current data on early Earth's environment." That is a good summary of the previous chapter.
p 111 List of the criteria for successful development of life even after prebiotic compounds were available.
p 111 Uses implausibility of producing cytosine, ribose and high-energy phosphates as examples of fact that early Earth failed to meet the important chemical requirements for development of life.
p 115 Analysis of "metabolism first" scenarios, presenting problems revealed by researchers, and concluding that they are very unlikely.
p 116 Discusses "replication first" scenarios and the major problems to such scenarios on the early Earth.
p 117 RNA assembly on mineral surfaces can be accomplished in carefully controlled laboratory environments, but they do not resemble early Earth conditions.
p 118 RNA world analyzed. Some success in laboratory, but requires strict control and synthetic skill.
Ch. 9 Look! Only One Hand!
p124 19 of the 20 amino acids in life on the Earth are left handed, the 20th having no chiral symmetry. The two sugars are right handed only. Any ordinary synthesis of amino acids produces an equal mixture of right and left-handed molecules, called a racemic mixture. While life is composed of left-handed amino acids, no natural process is known which will produce such a purely homochiral result.
p 125 Only photochemistry with circularly polarized light, or parity violations in nuclear interactions are known to produce a preference.
p 125 "Organic chemist William Bonner offered this summation 'I spent 25 years looking for a terrestrial mechanism for homochirality and trying to investigate them and didn't find any supporting evidence. Terrestrial explanations are impotent or nonviable.'"
p 126 Formation on mineral surfaces produces limited chiral enrichment, but other crystal surfaces of the same mineral would produce the opposite. So only microscopically local regions would achieve any enrichment, a situation that could not produce the homochiral reservoirs of amino acids and sugars.
p 126 Astronomical sources such as neutron stars can produce circularly polarized radiation, but not much promise there of pure homochirality.
p 128 Kuhn-Condon Rule - circularly polarized radiation must be monochromatic, since different frequencies produce different chirality, so broad-band radiation produces no net chirality.
p 129 The lack of a chiral source on Earth has prompted looks into space, but no amino acids have been found in space.
p 120 Murcheson meteorite has lots of amino acids, with a slight excess of left handed amino acids, but its not clear whether or not that excess is from earthly contamination. 74 amino acids. Nakhla meteorite fell in Nile River Delta in 1911, same amino acids as surroundings - so contamination is major problem. Even Tagish Lake meteorite from northern Canada was not free of contamination problems.
p 131 Since no terrestrial mechanism for homochirality can be found, one looks to space, but even if homochiral amino acids came in from space, they would be rendered racemic by a thousand years at 122F or one million years at 32F under dry conditions, and faster conversion in water or other media. So even if it were formed extraterrestrially, transporting it to Earth without mixing would be a problem.
p 132 Interesting discussion of the international meeting ISSOL 1999 where chirality was one of the main topics,
Ch. 10 The Codes of Life
A general discussion of the near impossibility of randomly generating a protein. Cites Bradley and Thaxton.
p 149 Example of cytochrome-C.
Ch. 11 Beneficial Boundaries
p143 Starts with a general description of the phospholipid bilayer, 3.5-4nm thick.
p148 fluid mosaic model with proteins in certain domains, an intricate biosystem
p 148 Fischer-Tropsch reaction to produce ambiphilic compounds. Models of membrane formation on early Earth
p 150 Active investigation and modeling of alternative scenarios for forming the first cell membranes, including extraterrestrial seeding. Discussion of the complexity of the membranes and the problems of self-synthesis in the early Earth environment.
p154 Discussion of the fine-tuned conditions for maintaining lipid bilayer structures in living organisms.
Ch. 12 Life's Minimal Complexity
Discusses Collins and the Human Genome Project, then the determination of the genomes of bacteria.
p 161 Table of genome sizes for bacteria, ranging from about 1500 to 1900 gene products.
p 163 Life's minimum - part of a detailed discussion of what would have to function together for viable life, shaking down to a bare minimum of around 250 parts that would have to be in place and function together.
Ch. 13 Extreme Life
Discusses the gamut of extremophiles and whether or not any of them could have been the first life.
p172 Table of the types of extremophiles.
A detailed description of the types, the conditions, and the challenges to them being the first life.
Ch. 14 Life on Mars?
p 183 Discusses Sagan's incredible optimism that life could arise anywhere. I always look favorably on any treatment that bad-mouths Sagan - I was always so offended by his arrogance.
p 183-190 Extensive discussion of the "rock celebrity", meteorite ALH840001 from Mars, found in the Allan Hills region of Antarctica and investigated after 9 years sitting in a vault. It came into public discussion on Aug 7, 1996 with a NASA announcement that they had found four indicators of life: carbonate globules, PAHs (polycyclic aromatic hydrocarbons), magnetic mineral crystals, elongated ovoids resembling microfossils.
p 184 Dated at 4.56+/-0.13 Gy by K-Ar, with a Rb-Sr date of 4 Gy suggesting a partial melt at that time. Made it oldest known rock, with other Mars meteorites dating no more than 1.3 Gy. That age put it in the warmer and wetter period of Mars history, it being assessed as having gone dry and cold at about 3.8 Gy.
p 184 Interesting evidence that meteorite was indeed from Mars. Mass spec analysis of gas bubbles perfectly matched Mars atmosphere, iron oxides, iron sulfides and oxygen isotope ratios matched those found in 11 other Martian meteorites.
p 185 Discussion of fall from fame as all four evidences for life evaporated. Finally led one geologist to lament "I never bought the reasoning that the compounding of inconclusive arguments is conclusive."(p190)
p 185-186 Carbonates from shock melting, not from biology, date to late heavy bombardment time
p 186 PAHs pooh-poohed as non biological, and besides contained C14, showing that they were of recent origin.
p 187 magnetites studies, biological origin should not be invoked
p 188 notorious nanobacteria judged to be imaging artifacts, at 20nm too small to be life forms.
p 190-194 Interesting discussion of conditions on Mars and the challenges to life formation there. Judgment was that it would have been much more difficult for life to arise there than on the Earth. Some interesting physical arguments.
p 195 RTB model predictions. More likely to find Earth life on Mars than vice versa.
p 196 "follow the water" directs researchers to Europa and beyond.
Ch. 15 Europa and Beyond
p 197 "scientists gaze into the heavens looking for a more likely cradle of life."
p 197 Europa is thought to have rocky core surrounded by a water shell some 150 km deep. Water 15% of Europa's mass compared to 0.02% of Earth's. Comets about 75% water, and Jupiter's moons Ganymede and Callisto some 65% water, but Europa is richest in liquid water, a requirement for life.
p 198 Interesting details on Europa - not enough radioactive materials to heat water enough to melt, tidal friction from its close orbit to Jupiter is thought to provide enough energy for some ice melting.
p 199 Presence of liquid water one of >150 requirements necessary for the survival of life.
p 199 May have necessary CHON molecules, but energy source for driving metabolism, growth, repair and reproduction seems to be missing. Tidal heating only 1/16 that of Io, so geothermal not a viable option.
p 199 - 201 Even if geothermal were sufficient, even Earth's thermal vent life requires oxidants from surface oxygen-based life to survive. Discusses need for oxidants. Thick ice seems to block any proposed mechanism for providing oxidants on Europa. Oxygen-ultraviolet paradox seems to drive the last nail in the coffin of an Europa origin of life model.
p 201 Shifts focus to Titan, largest moon of Saturn. Only solar system body with a large quantity of hydrocarbons in its atmosphere, and only body besides Earth with a large quantity of atmospheric nitrogen.
p 201 On negative side, hydrocarbons are transient at the poles, and though nitrogen-rich, ammonia has not been detected. Also lacks oxygen. No indigenous water. Not enough oxygen for prebiotic chemistry to work.
p 202 What about outer space models? Arrhenius proposed panspermia in 1907. But Arrhenius assumed infinite age for universe, and a universe only 3x more ancient than Earth does not give much of an enhancement for the development of life elsewhere.
p 203 Trying to find a transport mechanism for extraterrestrial life faces many problems. A major one is radiation - solar-wind-type mechanisms may move dust grains, but also subject life to sterilizing radiation.
p 203 Export of Earth Life box.
p 204 RTB model suggests failure of solar system and panspermia models.
Ch. 16 Life, Seeded on Purpose
p 205 "At ISSOL 1999, one scientist ... frustrated .. proposed the idea of directed panspermia" Also Orgel, and Francis Crick expanded on the concept in his "Life Itself". "book's tone suggests that the evidence leaves no alternative but to consider directed panspermia as an explanation for life on Earth."
p 205 Thirty years since Orgel and Crick "naturalistic explanations ... have grown in both number and creativity ... credibility ... has waned"
p 206 Cambrian explosion also cited as evidence against naturalistic explanation
p 206 Directed panspermia "admits that the origin of life requires a powerful, intelligent personal agency."
p 206-207 Argues that in the extremely unlikely scenario where life was created elsewhere, the problems of transporting it to Earth appear insurmountable.
p 207 Discusses SETI efforts. Scanned all 202 solar-type stars withing 155 lightyears. Pegs max velocity at .01c and 25,000 yr requirement to travel 250 lightyears.
p 208 RTB's model is supernatural panspermia
p 208 Box "Two Kinds of Miracles" those outside our observable universe, and those that act within God's chosen physical laws.
Ch. 17 Solving the Mystery
p 211 "why would the all-powerful, all-knowing, all-loving God of the Bible create microorganisms 3.8 billion years prior to creating human beings?" "why only microorganisms or colonies of microorganisms for the first 3.3 billion years of life history?" "how does one explain why life appeared at the earliest possible moment physics allowed? And why, given the natural assembly time for even the simplest organism, was life's introduction on Earth so sudden?"
p 211 Starts a very nice overview of the fine tuning. This chapter briefly summarizes many of the ideas in "Why the Universe Is the Way it Is".
p 211 "Putting a planet together" ... a very nice section. Required several billion years to obtain necessary isotopic enrichment. Began with H, 3 1/2 minutes to about 75/25 H/He, ignition of stars which manufactured the other elements, at least two generations of stars to sufficiently enrich the cloud from which the solar system formed. Need nearby Type I and Type II supernovae. Details about Sun's evolution.
p 214 Box on Climatic Runaways
p 215 Discusses greenhouse gas balances
p 215 Importance of plate tectonics, radioactive heating, and the geodynamo as conditions for sustaining life.
p 217 Steps that protected life, including concentration of essential trace elements by early bacteria.
p 218 Box "A Brighter Young Sun"
p 219 Provided for Life -- soil and atmosphere enrichment processes. Role of cyanobacteria, discussion of banded iron, use of early life to prepare for more complex life.
p 221 "Human beings reap the benefit of nearly 4 billion years' worth of biodeposits."
p 223 A summary of the features that "build to a preponderance of evidence for the design and craftmanship of a Creator."