Even Abiogenesis seems to be fraught with difficulties.
Scientific Facts and Solution
1. Homochirality somehow arose in the sugars and amino acids of prebiotic soups, although there is no mechanism by which this can occur (1) and is, in fact, prohibited by the second law of thermodynamics (law of entropy). (2)
Solution - reject the second law of thermodynamics
2. In the absence of enzymes, there is no chemical reaction that produces the sugar ribose (1), the "backbone" of RNA and DNA. "science of the gaps"
Chemical reactions in prebiotic soups produce other sugars that prevent RNA and DNA replication (1).
Solution - discard chemistry data
"science of the gaps"
3. Pyrimidine nucleosides (cytosine and uracil) do not form under prebiotic conditions and only purine (adenine and guanine) nucleosides are found in carbonaceous meteorites (1) (i.e., pyrimidine nucleosides don't form in outer space either).
Solution - discard chemistry data
"science of the gaps"
4. Even if a method for formation of pyrimidine nucleosides could be found, the combination of nucleosides with phosphate under prebiotic conditions produces not only nucleotides, but other products which interfere with RNA polymerization and replication (1).
Solution - discard chemistry data
"science of the gaps"
5. - Purine and pyrimidine nucleotides (nucleosides combined with phosphate groups) do not form under prebiotic conditions (3).
solution - discard chemistry data
"science of the gaps"
6. Neither RNA nor DNA can be synthesized in the absence of enzymes "science of the gaps"
Enzymes cannot be synthesized in the absence of RNA and ribosomes. "science of the gaps"
Nucleosides and amino acids cannot form in the presence of oxygen, which is now known to have been present on the earth for at least four billion years (4), although life arose at least ~3.5 billion years ago (5).
Solution - discard geological data
discard chemistry data
7. Adenine synthesis requires unreasonable HCN concentrations. Adenine deaminates with a half-life of 80 years (at 37?C, pH 7). Therefore, adenine would never accumulate in any kind of "prebiotic soup." The adenine-uracil interaction is weak and nonspecific, and, therefore, would never be expected to function in any specific recognition scheme under the chaotic conditions of a "prebiotic soup." (6)
Solution - discard chemistry data
8. Cytosine has never been found in any meteorites nor is it produced in electric spark discharge experiments using simulated "early earth atmosphere." All possible intermediates suffer severe problems (7). Cytosine deaminates with an estimated half-life of 340 years, so would not be expected to accumulate over time. Ultraviolet light on the early earth would quickly convert cytosine to its photohydrate and cyclobutane photodimers (which rapidly deaminate) (8).
Solution - discard geological data
discard chemistry data
9. Mixture of amino acids the Murchison meteorite show that there are many classes of prebiotic substances that would disrupt the necessary structural regularity of any RNA-like replicator (9). Metabolic replicators suffer from a lack of an ability to evolve, since they do not mutate (10).
Solution - discard chemistry data
10. The most common abiogenesis theories claim that life arose at hydrothermal vents in the ocean. However, recent studies show that polymerization of the molecules necessary for cell membrane assembly cannot occur in salt water (11). Other studies show that the early oceans were at least twice as salty as they are now (12)
Solution - Life arose in freshwater ponds (even though the earth had very little land mass), using some unknown mechanism.
11. Comparison of the dates of meteor impacts on the moon, Mercury, and Mars indicate that at least 30 catastrophic meteor impacts must have occurred on the earth from 3.8 to 3.5 billion years ago (13). These impacts were of such large size that the energy released would have vaporized the entirety of the earth's oceans (14), destroying all life.
Solution - Life spontaneously arose by chance at least 30 separate times, each within a period of ~10 million years.
References
1. Orgel, L. 1994. The origin of life on earth. Scientific American. 271 (4) p. 81. (Dr. Orgel is an atheist who has been working on origins of life research for over 30 years.)
2. This argument has nothing to do with the closed/open system question. The 2nd law of thermodynamics states that heat flows from hot bodies to cold bodies. This law also affects the formation of enantiomers in chemical reactions capable of producing stereoisomers. Since the formation of both left- and right-handed enantiomers requires the exact same amount of energy, both enantiomers are produced in identical amounts. Any deviation from this result is highly unlikely (much less likely than the scenario of starting your car on a hot California day and having freeze over while running).
Some researchers have cited the possibility of differential synthesis of one enantiomer over another in the presence of circularly polarized light. There are a couple problems with this theory. First, there is no source of this kind of light in the vicinity of our solar system. Second, the demonstration of circularly polarized light was found only in the infrared region of the spectrum. Light must be of much more energetic wavelengths (ultraviolet). Third, if stereoisomers were formed, the energy of the light would break them down within a short period of time.
3. Orgel, L. 1994. The origin of life on earth. Scientific American. 271 (4) p. 82.
4. Bortman, H. 2001. Life Under Bombardment from the NASA Astrobiology Insititute. - Alternating layers of oxidized iron in the so-called banded iron formation from Akilia Island in West Greenland demonstrates that free oxygen has been present on earth longer than 3.85 billion years.
Dimroth, E. and M. Kimberley. 1970. Can. J. Earth Sci., 13:1161.
Carver, J. H. 1981. Prebiotic atmospheric oxygen levels. Nature 292: 136-138.
5. Schopf, J.W. 1993. Science 260: 640-646.
M. T. Rosing, Science 283, 674 (1999).
6. Shapiro R. 1995. The prebiotic role of adenine: a critical analysis. Orig. Life Evol. Biosph. 25: 83-98.
7. Cytosine intermediates suffer the following problems:
a. Synthesis based upon cyanoacetylene requires the presence of large amounts of methane and nitrogen, however, it is unlikely that significant amounts of methane were present at the time life originated.
b. Synthesis based upon cyanate is problematical, since it requires concentrations in excess of 1 M (molar). When concentrations of 0.1 M (still unrealistically high) are used, no cytosine is produced.
c. Synthesis based upon cyanoacetaldehyde and urea suffers from the problem of deamination of the cytosine in the presence of high concenrations of urea (low concentrations produce no cytosine). In addition, cyanoacetaldehyde is reactive with a number of prebiotic chemicals, so would never attain reasonable concentrations for the reaction to occur. Even without the presence of other chemicals, cyanoacetaldehyde has a half-life of only 31 years in water.
8. Shapiro, R. 1999. Prebiotic cytosine synthesis: A critical analysis and implications for the origin of life. Proc. Natl.Acad. Sci. USA 96: 4396-4401.
9. Shapiro, R. 2000. A replicator was not involved in the origin of life. IUBMB Life 49: 173-176.
10. Monnard, P.-A, C. L. Apel, A. Kanavarioti and D. W. Deamer. 2002. Influence of ionic solutes on self-assembly and polymerization processes related to early forms of life: Implications for a prebiotic aqueous medium. Astrobiology 2:213-219.
11. Szathm?ry, E. 2000. The evolution of replicators. Philosophical Transactions: Biological Sciences 355: 1669-1676.
Knauth, L.P. 2000. Life on Land in the Precambrian and the Marine vs. Non-Marine Setting of Early Evolution. First Astrobiology Science Conference, April 3-5, 2000, NASA Ames Research Center, 403 (Abstract 353).
12. Knauth, L.P. 2002. Early Oceans: Cradles of Life or Death Traps? Astrobiology Science Conference 2002, April 7-11, NASA Ames Research Center. p. 9.
13. Chyba, C. and C. Sagan. 1992. Endogenous production, exogenous delivery and impact-shock synthesis of organic molecules: an inventory for the origins of life. Nature 355: 125-132
14. Kerr, R. 1999. Early Life Thrived Despite Earthly Travails. Science 284: 2111-2113. "For its first half-billion years, Earth endured a punishing rain of impacts, which vaporized the oceans and scorched the globe so fiercely that some researchers now propose that life could have first evolved on a more hospitable world, then later hitchhiked to Earth on a meteorite."
"A few of these impactors were probably 500 kilometers in diameter--big enough to create a superheated atmosphere of vaporized rock that would in turn have vaporized the oceans for 2700 years and sterilized even the subsurface, say Sleep and Zahnle."
Sleep, N.H., K.J. Zahnle, J.F. Kasting, and H.J. Morowitz. 1989. Annihilation of ecosystems by large asteroid impacts on the early Earth. Nature 342: 139-142.
Regards,
Blacknad.
