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Transcript
II Peter 3:3-5 3 Knowing this first, that there shall come in the last days scoffers, walking after their own lusts, 4 And saying, Where is the promise of his coming? For since the fathers fell asleep, all things continue as they were from the beginning of the creation. 5 For this they willingly are ignorant of, that by the word of God the heavens were of old, and the earth standing out of the water and in the water: ©2000 Timothy G. Standish Theories On The Origin Of Life Timothy G. Standish, Ph. D. ©2000 Timothy G. Standish What Does “Evolution” Mean? “Evolution” has at least three (3) distinct meanings: The fact of evolution - Organisms were different in the past than they are today – Fossil record – Biblical record - God’s curse on Adam Genesis 3:18 Thorns also and thistles shall it bring forth to thee: and thou shalt eat the herb of the field: The theory of evolution - Natural selection – At least partially supported by population genetics accounting for changes in allelic frequencies within populations The doctrine of evolution - All that we see can be accounted for by natural random events and thus a Designer is not necessary. ©2000 Timothy G. Standish Arguments for a Designer Organisms look designed for at least three (3) reasons: Redundancy - A Designer can engineer redundancy into a system, but chance is unlikely to do this. An example of this is the presence of degeneracy in the genetic code and other features that minimize or negate the effects of many point mutations. Excess potential - Organisms have potential that may never be used. For example, Wallace, co-discoverer of natural selection, pointed out that primitive people have the capacity to do calculus when trained. Natural selection is unlikely to select for capacity that is not used. Complexity - Life is so complex that it is improbable it came about by chance. ©2000 Timothy G. Standish The Likely and the Unlikely In general arguments for a designer are arguments against the alternative. This does not mean these are just arguments against evolutionary theory. All arguments, by definition, are characterized by taking one side while arguing against another side. Arguments against a theory are about eliminating possible explanations. There is nothing inferior about this, in fact, it is deductive reasoning which is used by scientists all the time in their quest for truth. Arguments for a Designer generally revolve around probability. Meaningful complexity is unlikely to result from random events. Organisms are meaningfully complex. Some claim that natural selection overcomes much of this problem as, while change may be random, selection is not. Science is about predicting what is likely and what is unlikely. Everyone is in agreement that the events leading to production of living organisms are unlikely. ©2000 Timothy G. Standish What This Talk Is Actually About In this talk we will look at the mechanisms proposed for the origin of living systems in the absence of a designer. We will then look at one of the many biochemical systems that must be in place in all organisms. Finally we will compare the information we have on organisms at the molecular level, and see whether it is best explained as the result of natural selection or design. ©2000 Timothy G. Standish In a Long Time and Big Universe It has been argued that given massive lengths of time and a universe to work in, the unlikely becomes likely: Given infinite time, or infinite opportunities, anything is possible. The large numbers proverbially furnished by astronomy, and the large time spans characteristic of geology, combine to turn topsy-turvy our everyday estimates of what is expected and what is miraculous. Richard Dawkins (1989) The Blind Watchmaker: Why the evidence of evolution reveals a universe without design. W. W. Norton and Co. New York. p139. ©2000 Timothy G. Standish Understanding Complexity Allows Better Estimates of Probability At Darwin’s time, his explanation for the origin of organisms seemed reasonable as their complexity was not understood fully. “First simple monera are formed by spontaneous generation, and from these arise unicellular protists . . .” The Riddle of the Universe at the close of the Nineteenth Century by Ernst Haeckel, 1900. ©2000 Timothy G. Standish Little or Big Changes? Not all changes improve fitness, they may: – Improve the fitness of an organism (very unlikely) – Be neutral, having no effect on fitness – Be detrimental, decreasing an organisms fitness (most likely) The bigger the change the more likely it is to be significantly detrimental Darwin argued that evolution is the accumulation of many small changes that improve fitness, big changes are unlikely to result in improved fitness. “Many large groups of facts are intelligible only on the principle that species have been evolved by very small steps.” – The Origin of Species Chapter VII under “Reasons for disbelieving in great and abrupt modifications” ©2000 Timothy G. Standish Behe’s Insight Michael Behe contends that when we look at the protein machines that run cells, there is a point at which no parts can be removed and still have a functioning machine. He called these machines “irreducibly complex.” We encounter irreducibly complex devices in everyday life. A simple mouse trap is an example of an irreducibly complex device: Staple Trigger Hammer Board Cheese Bait holder Spring ©2000 Timothy G. Standish Irreducibly Complex Protein Machines Cells are full of irreducibly complex devices - Little protein machines that will only work if all the parts (proteins) are present and arranged together correctly. Natural selection does not provide a plausible mechanism to get from nothing to the collection of parts necessary to run a number of irreducibly complex protein machines needed to have a living cell Evolution of these protein machines must occur in single steps, not gradually, as to be selected a protein must be functional in some way. Each protein machine is fairly complex, thus evolution in a single step seems unlikely. ©2000 Timothy G. Standish Chemical Evolution ©2000 Timothy G. Standish Four Postulated Stages of Chemical Evolution Chemical evolution is the spontaneous production of the molecular components of cells that had to be produced prior to evolution of the first cell: 1) Abiotic synthesis of organic monomers 2) Abiotic synthesis of organic polymers 3) Self assembly of protobionts 4) Evolution of a genetic system We will concentrate on the first two steps ©2000 Timothy G. Standish Step 1: Abiotic Synthesis of Organic Monomers The monomers that make up polymers in living cells are reduced carbon compounds Can’t happen in modern world due to oxidizing atmosphere 1920s A. I. Oparin (Russia) and J. B. S. Haldane (Great Britain) postulated that as spontaneous synthesis of reduced organic molecules is impossible in an oxidizing environment, the earth must have had a reducing atmosphere 1953 Miller and Urey designed a device to test the hypothesis that given the right conditions, organic monomers could be produced ©2000 Timothy G. Standish JBS Haldane While Haldane was one of the founders of population genetics, it is worth mentioning that he was a screwball of the first order: – Just before the 1925 signing of the Geneva protocol banning chemical weapons, Haldane came out as an advocate of chemical warfare – He was a racist who believed blacks were immune to chemical weapons and thus should be used as the frontline troops in wars (with white officers to lead them of course) – As England had access to black troops from the colonies, this would give them an advantage over Germany in future chemical wars ©2000 Timothy G. Standish The Miller-Urey Device NH3 H 2 CH4 H2O Sample ©2000 Timothy G. Standish Products of Miller and Urey’s Device After several days of operation, the Miller-Urey device produced a brown organic substance in which, either in this experiment or subsequent variations, was found many of the basic building blocks of: – – – – Proteins (amino acids) Nucleic acids (ribose, purines and pyrimidines) Polysaccharides (sugars) Fats (fatty acids and glycerol) Note that it was the building blocks that were found, not the actual macromolecules Along with these building blocks, there were many other molecules not found in organisms ©2000 Timothy G. Standish Did Miller and Urey Prove Chemical Evolution? Six reasons that it does not prove chemical evolution: Oparin’s reducing conditions were postulated because they are conditions allowing reduced organic molecule production, not because of compelling evidence these conditions ever existed on earth. Reduced organic products were not the result of random chance, but of a device that had been carefully designed and constructed. Products were not enriched in the chemicals that make up organisms. This is a particular problem when it comes to stereoisomers. No organisms were actually made. Even if organisms were made in this way, this would not prove it to be how things actually happened, it only shows it to be one possible way. Accumulation of organic monomers is only the first step in chemical evolution. ©2000 Timothy G. Standish Step 2: Abiotic Synthesis of Organic Polymers It has been postulated that the monomer building blocks produced under conditions resembling those in the MillerUrey experiment were joined together to make polymers Experiments have been done that demonstrate this is possible in the absence of living cells or cell products like enzymes The sequence in which monomers are joined together to make polymers is vital to the function of polymers like DNA and proteins. No mechanism has been proposed for joining monomers in meaningful sequences, thus abiotically synthesized organic polymers are assumed to have been random in sequence. ©2000 Timothy G. Standish A Polymerization Experiment Imai et al, 1999 Science 283:831-883 Imai et al’s device “simulated the pressure and temperature conditions of the hydrothermal circulation of water” “However, there were still some large differences [from real hydrothermal vents], for instance, in pH, CO2, Na and Cl contents.” 100 mM glycine in pure water was circulated in the system alternating temperature and pressure with each circuit 2 mM diketopiperazine, 1mM triglycine and 0.4 mM diglycine resulted once close to steady state condtions were reached In the presence of Cu++ and low pH, small 0.001 mM concentrations of up to hexaglycine were produced ©2000 Timothy G. Standish Imai et al’s Device Heating Cooling Depressurization Pressurization Sample removal ©2000 Timothy G. Standish Random Sequences are Unlikely to be Meaningful or Useful Random sequences of amino acids are analogous to random sequences of letters: – ldjfire vireahdftrfd – grvcnlkertpoildrirti – ugcrtrrtadhk jjkvhvf – jmvcbkvbkjhcguvdrttr – k jfvukvfkhjfvkhj he Random sequences are unlikely to be meaningful ©2000 Timothy G. Standish Meaningful Sequences are Unlikely Even a short meaningful phrase is a very unlikely sequence of letters For example, “In the beginning God” is only 20 letters long, but is very unlikely to be produced by random typing of letters Ignoring capitalization, and assuming each letter is equally probable, the probability that the first character will be “I” is 1/27 (26 letters in the alphabet plus the space makes 27) The probability that the correct letter will be at each position is: 20 1 2.36 10 29 27 This is 0.0000000000000000000000000000236 Or about 1 chance in 50,000 trillion trillion ©2000 Timothy G. Standish Is this a Fair Estimate of Probability? No! There are a number of ways in which this phrase can have the same meaning: – God, in the beginning – In the beginning was the Word – Before everything God The same is true for proteins, in some areas of most proteins, there can be a small amount of variability, in other areas, there can be no change in the sequence of amino acid monomers ©2000 Timothy G. Standish Does this Make Production of Functional Proteins Likely? No! Lets look at an example, the enzyme Glyceraldehyde-3phosphate dehydrogenase: The Mycoplasma genitalium G-3-P dehydrogenase protein sequence: – MAAKNRTIKV AINGFGRIGR LVFRSLLSKA NVEVVAINDL TQPEVLAHLL KYDSAHGELK RKITVKQNIL QIDRKKVYVF SEKDPQNLPW DEHDIDVVIE STGRFVSEEG ASLHLKAGAK RVIISAPAKE KTIRTVVYNV NHKTISSDDK IISAASCTTN CLAPLVHVLE KNFGIVYGTM LTVHAYTADQ RLQDAPHNDL RRARAAAVNI VPTTTGAAKA IGLVVPEANG KLNGMSLRVP VLTGSIVELS VVLEKSPSVE QVNQAMKRFA SASFKYCEDP IVSSDVVSSE YGSIFDSKLT NIVEVDGMKL YKVYAWYDNE SSYVHQLVRV VSYCAKL ©2000 Timothy G. Standish Why Random Production of Glyceraldehyde-3-Phosphate Dehydrogenase is Improbable There are 337 amino acids strung together to make the Mycoplasma genitalium G-3-P dehydrogenase protein At each position in the string there could be any one of 20 amino acids Probability of making this protein using random synthesis is (1/20)337 = 3.5 x 10-439 or 1 chance in 2.9 x 10-438 Even if there are a trillion trillion ways of making G-3-P dehydrogenase, that only lowers the probability of making a functional protein to 3.5 x 10-415 ©2000 Timothy G. Standish 3.5 x 10-439 Is A Very Small Number 0.000000000000000000000000000000000000000 00000000000000000000000000000000000000000 00000000000000000000000000000000000000000 00000000000000000000000000000000000000000 00000000000000000000000000000000000000000 00000000000000000000000000000000000000000 00000000000000000000000000000000000000000 00000000000000000000000000000000000000000 00000000000000000000000000000000000000000 00000000000000000000000000000000000000000 00000000000000000000000000000035 ©2000 Timothy G. Standish Where G-3-P Dehdrogenase Fits Into the Scheme of Life All cells contain a biochemical pathway that converts sugar to energy The first part of this pathway is called the glycolytic (sugar splitting) pathway Sugar is taken in at the start of the pathway and the products are energy in the form of ATP, a chemical called pyruvate and another chemical called NADH. Glyceraldehyde-3-phosphate dehdrogenase is one of the enzymes in the glycolytic pathway. ©2000 Timothy G. Standish The Glycolytic Pathway ATP 1 2 3 4 5 6 7 8 9 10 Pyruvate Each step in the pathway represents a small change in the sugar molecule As these small changes are made, the sugar is slowly turned into something different Glyceraldehyde-3-phosphate dehydrogenase is found at step 6 in the glycolytic pathway ATP Sugar NAD+ NADH ADP+P ATP ADP+P ATP ©2000 Timothy G. Standish What Actually Happens At Step 6 By the time step 6 is reached, the 6 carbon sugar molecule has been split into two three carbon molecules called glyceraldehyde-3H H phosphate | | CH2OH H HO H OH O H OH OH H H C=O C=O | | H-C-OH H-C-OH | | C CH2-O-P H2-O-P Glyceraldehyde-3-Phosphate Glucose In step 6 of glycolysis, glyceraldehyde-3-phospate is converted to 1,3-bisphosphoglycerate and oxidized nicotinomide adenine dinucleotide phosphate (NAD+) is reduced H | C=O | H-C-OH | CH2-O-P + NAD+ + P Glyceraldehyde-3-Phosphate P-C=O | H-C-OH | CH2-O-P + NADH 1,3-Bisphosphoglycerate ©2000 Timothy G. Standish From G-3-P to 1,3-BPG In Four Easy Steps NADH NAD+ S C-O| H- C-OH | CH2-O-P NADH S C-O- | H- C-OH | CH2-O-P P NAD+ S NAD+ S H| C=O | H- C-OH | CH2-O-P H | C=O | H-C-OH | CH2-O-P P- C=O | H- C-OH | CH2-O-P P- C=O | H- C-OH | CH2-O-P 1,3Bisphosphoglycerate Glyceraldehyde3-Phosphate ©2000 Timothy G. Standish Summary To convert G-3-P to 1,3-bisphosphoglycerate all of the following components must be present: – – – – The enzyme - Glyceraldehyde-3-phosphate dehydrogenase NAD+- Oxidized Nicotinamide Adenine Dinucleotide Phosphate Glyceraldehyde-3-phosphate This reaction would be pointless in the absence of the next step in the glycolytic pathway, the production of ATP catalyzed by phosphoglycerokinase A separate set of reactions is necessary to regenerate the NAD+ from NADH ©2000 Timothy G. Standish NAD+ H O C O HO NH2 N CH2 O O P O OH OH HO NH2 O P OH N O CH2 OH N O N N OH ©2000 Timothy G. Standish What Does This Mean? The glycolytic pathway is central to life The components needed for step 6 are unlikely to have all come about via chemical evolution (random processes) particularly glyceraldehyde-3-phosphate dehydrogenase Natural selection could not work on the enzyme glyceraldehyde-3-phosphate dehydrogenase in the absence of the other enzymes in the glycolytic pathway as this reaction is pointless without the subsequent reactions Chemical evolution combined with natural selection does not provide a convincing mechanism for the production of components needed for step 6 in the glycolytic pathway The same could be said for the other 9 steps in the glycolytic pathway ©2000 Timothy G. Standish Yes, It Is Unlikely . . . But The argument is not that the origin of life was an unlikely event, but that given sufficient time and resources chance events could produce the first organism that could then be acted on by the guiding hand of natural selection So what are the resources available for the production of the first/simplest organism? Is it really the universe? “The Monera (for instance, chromacea and bacteria), which consist only of this primitive protoplasm, and which arise by spontaneous generation from these inorganic nitrocarbonates, may thus have entered upon the same course of evolution on many other planets . . .” – The Riddle of the Universe at the close of the Nineteenth Century by Haeckel. ©2000 Timothy G. Standish Space and Time The conditions necessary to produce reduced carbon compounds like those produced in the Miller-Urey experiment have not, so far, been found elsewhere in the universe In reality, the conditions needed for life seem to only be present in a tiny fraction of the universe and we happen to be living on it. Time is the other element needed, and this is a real problem Even if the conventional interpretation of the fossil record is used, life seems to have appeared very soon (a few million, not billions of years) after water appeared on earth ©2000 Timothy G. Standish Conventional History Of The Earth 0 1,000 Human fossils Last dinosaur fossils First reptile fossils First land plant fossils -First multicellular animal fossils 1,500 -First eukaryotic fossils Cenozoic Millions of Years BP Mesozoic 500 Paleozoic 2,000 Precambrian 2,500 3,000 3,500 -Atmospheric Oxygen accumulation (from cyanobacteria) 4,000 -First fossil prokaryotes Origin of life -Crust forms 4,500 -Formation of the earth ©2000 Timothy G. Standish When Was The Earth Sterile? Recent explorations of the oldest known rocks of marine sedimentary origin from the southwestern coast of Greenland suggest that they preserve a biogeochemical record of early life. On the basis of the age of these rocks, the emergence of the biosphere appears to overlap with a period of intense global bombardment. This finding could also be consistent with evidence from molecular biology that places the ancestry of primitive bacteria living in extreme thermal environments near the last common ancestor of all known life. Stephen J. Mojzsis, T. Mark Harrison. Vestiges of a Beginning: Clues to the Emergent Biosphere Recorded in the Oldest Known Sedimentary Rocks. GSA Today, April 2000, 10(4), 1-?? ©2000 Timothy G. Standish Newer Ideas Mars may have served as life’s incubator as it cooled before earth and had a moist environment. Life, in the form of bacteria or bluegreen algae, was transferred to earth when chunks of Mars knocked off by collisions with comets etc. fell to earth. This general idea is not new. Francis Crick called it “panspermia” in Life Itself where he says the earth was seeded with life from space (Hoyle may also have published something similar) None of this makes explanations simpler, just more complex (should Ockham’s Razor be invoked?) ©2000 Timothy G. Standish But There’s More A Lot More The organism Mycoplasma genitalium from which the G-3-P dehydrogenase we looked at came from is the simplest known “free living” organism (although it is a parasite) M. genitalium has a genome of 580,070 bp (humans have about 3,000,000,000) The calculated number of proteins (genes) in this the simplest known organism, is 470 The average size of M. genitalium proteins is about 350 amino acids (in the ball park of G-3-P dehydrogenase) Even if enough time and space existed to generate a minimally functional G-3-P dehydrogenase, this is just the tip of the ice burg M. genitalium has to be close to irreducibly complex. Conditions under which a less complex organism could exist are just about as improbable as generating the organism in the first place and present a host of other problems ©2000 Timothy G. Standish Conclusions Life is far more complicated than was anticipated by the originators and early defenders of natural selection as a mechanism for life’s origin independent of a Creator Natural selection does not provide a convincing mechanism for the origin of biochemical pathways and other molecular machines basic to life Claims that almost infinite amounts of time and space could account for the improbable origin of life seem less convincing in light of current exploration of space and understanding of the fossil record Creationists can accept change over time and natural selection as a mechanism for small changes, but, in light of current knowledge faith in a Creator of life remains well founded ©2000 Timothy G. Standish Psalms 8:3-6 3 When I consider thy heavens, the work of thy fingers, the moon and the stars, which thou hast ordained; 4 What is man, that thou art mindful of him? and the son of man, that thou visitest him? 5 For thou hast made him a little lower than the angels, and hast crowned him with glory and honour. 6 Thou madest him to have dominion over the works of thy hands; thou hast put all things under his feet: ©2000 Timothy G. Standish The Information Catch 22 With only poor copying fidelity, a primitive system could carry little genetic information without L [the mutation rate] becoming unbearably large, and how a primitive system could then improve its fidelity and also evolve into a sexual system with crossover beggars the imagination." Hoyle F., "Mathematics of Evolution", [1987], Acorn Enterprises: Memphis TN, 1999, p20 ©2000 Timothy G. Standish Evolution . . . So 20th Century "In the realm of science, scholars such as William Dembski and Michael Behe have been demonstrating how the order in the universe is evidence that it has been intelligently designed. 'No!' say the Darwinists. 'Everything has to be random!' But the evolutionists are the ones who sound so outdated, so 20th century.” Veith, Gene E. Reality makes a comeback. World Magazine Feb. 12, 2000 Volume 15 Number 6 ©2000 Timothy G. Standish ©2000 Timothy G. Standish RNA World The 'RNA world' scenario hinges on some rather farfetched assumptions about the catalytic ability of RNA. For example, RNA polymerase ribozymes must have been responsible for replicating the ribozymes of the RNA world, including themselves (via their complementary sequences). RNA replication is a very challenging set of reactions -far more challenging than those yet known to be catalyzed by RNA. David P. Bartel and Peter J. Unrau, "Constructing an RNA World." Trends in Biochemical Sciences 24 (1999):M9M13. ©2000 Timothy G. Standish