Life on purpose

For centuries “fearfully and wonderfully made” were just words about our bodies from Psalm 139. Now we have proof: In The Miracle of the Cell, a WORLD 2020 Book of the Year honorable mention, biochemist Michael Denton shows how vast is the chasm between some chemical soup and a cell filled with genetic information encoded in the double helix, and much besides. In this excerpt, courtesy of Discovery Institute, he describes how discoveries of modern science strongly suggest the world was designed with Earth’s biological life in mind. —Marvin Olasky

An honest man, armed with all the knowledge available to us now, could only state that in some sense, the origin of life appears at the moment to be almost a miracle, so many are the conditions which would have to be satisfied to get it going.

—Francis Crick¹

There is something evocative and endlessly fascinating about the idea of a message sent to Earth from space by an advanced extraterrestrial civilization, revealing information about our own origin, existence, and place in nature. It is the stuff of many popular works, from Carl Sagan’s Contact and Stanley Kubrick’s 2001: A Space Odyssey to Erich von Däniken’s book Chariots of the Gods.

Although not the work of aliens, a very special chemical message regarding the place of carbon-based life in the universe did arrive on Earth on the night of September 28, 1969.² On that night, the sky over the small southeastern Australian town of Murchison was lit up by an exploding meteorite, which scattered fragments of rock over the nearby countryside. Subsequent chemical analyses of the meteorite’s fragments proved, for the first time, that at least some of the organic building blocks of life are being constantly synthesized in space and exist in vast quantities throughout the cosmos.³ Moreover, very recent analyses suggest the total number of different carbon compounds embedded in the meteorite may number in the tens of thousands and perhaps even millions.⁴

The Murchison meteorite revealed that the cosmos is seeded with a vast inventory of organic chemicals, including amino acids⁵ and nucleobases,⁶ the starting points in the assembly of the two main polymers—proteins and nucleic acids—in carbon-based organisms. Just how many of the basic organic building blocks of life might have been produced abiotically in space and brought to Earth in meteorites (or synthesized in the primeval ocean) is not clear. But more and more are being identified in meteorites and synthesized in the lab in simulated prebiotic conditions.⁷

More recent spectroscopic analyses of interstellar gas have revealed that the cosmos is seeded not just with some of the basic monomers of life, but also with far more complex carbon compounds. One class of complex carbon compound—the polycyclic aromatic hydrocarbons (PAHs)—is abundant throughout the cosmos, and some may contain up to one hundred carbon atoms.⁸ Some contain nitrogen (PANHs), forming heterocyclic compounds that have a chemical structure similar to the heterocyclic compounds used in living things, such as the nucleotide bases.⁹

It is not hard to see a parallel between Friedrich Wöhler’s landmark synthesis of urea in 1828 and the message the Murchison meteorite delivered. Wöhler undercut the need for a vital force in the cell for manufacturing the basic organic constituents of life, but their synthesis still required a cell or a chemist. The Murchison meteorite and subsequent study of other meteorites and spectroscopic analysis of interstellar space imply that the universe is replete with organics and that when the inventory is more fully known, it very well may contain many more of the basic building blocks of life. These have been synthesized, to paraphrase Wöhler, not only without a kidney, but even without a cell or a chemist. And these discoveries have, to a large extent, validated a widespread belief of origin-of-life researchers in the twentieth century, since Stanley Miller’s ground-breaking experiment in 1953, that the basic ingredients of life can be synthesized abiotically in nature.

The Miller-Urey experiment involved sending a spark through an atmosphere thought to mimic the atmosphere of the primeval Earth (water vapor, methane, ammonia, and hydrogen). The result was a complex chemical mix that contained glycine, alanine, and aspartic acid, three of the amino acids used in building proteins in modern organisms.¹⁰ Recent studies of his archived material from his original experiments subjected to more advanced analytical techniques show that ten of the twenty biologically important amino acids—lysine, alanine, serine, threonine, aspartic acid, valine, glutamic acid, methionine, isoleucine, and leucine—were present in Miller’s flasks.¹¹

Of course the three amino acids reported by Miller, and even the ten in the later accounting, are a long way from the inventory of monomers needed to assemble a living cell. Much less does it explain how the inventory of monomers were assembled to form the first cell. Nonetheless, Miller-type experiments and evidence from the analysis of meteorites such as the Murchison meteorite do show that at least some of the key building blocks of life can be, and indeed are, synthesized abiotically, and may be common throughout interstellar space. This is no small discovery. For they show that at least the first step towards the cell requires no more than “ordinary chemistry” and suggests that the subsequent steps to the cell might also be explicable in terms of the known laws of chemistry and physics—that nature might be sufficient.

Thus we see that the message brought to Earth that fateful September night, written in the chemistry of a falling star, is highly significant. As well as supporting the claim that life’s emergence might have been the result of entirely natural mechanisms, it also supports the thesis central to this book and the whole Privileged Species series: Carbon-based life as it exists on Earth is no contingent afterthought of nature, no artifactual accident, but an inherent part of the natural order. It is an inherent part of nature’s grand design from the moment of creation.

Cosmic Abundance

There is further evidence that life may be no contingent cosmic afterthought but an end programmed into the order of things from the beginning. The atoms carbon, oxygen, and nitrogen were among the first atoms synthesized in the stars. These joined hydrogen, already in existence, to make up the universe of organic chemicals, the substances upon which Earth’s whole carbon-based biosphere is built. (When Lawrence Henderson wrote his classic Fitness, the source of carbon, oxygen, nitrogen, and various other elements heavier than hydrogen and helium was a mystery, since the nuclear synthesis of the atoms of the periodic table in the interior of stars was only elucidated by Fred Hoyle and others in the mid-twentieth century.) These four atoms are also, along with helium, commonest of all atoms in the universe.¹²

Even a cursory observation of the cosmic abundance of the elements reveals an obvious correspondence between the cosmic pattern generated in the heart of the stars and life on Earth, between the cosmic order and the order of life, between man and cosmos. The elements hydrogen (H), carbon (C), oxygen (O), and nitrogen (N), the core atoms that combine to form the molecules of organic chemistry that compose 96 percent of the human body, are respectively the first, third, fourth, and fifth most abundant elements in the cosmos. And their order of abundance curiously corresponds to their abundance in the human body.¹³ Two of the three most abundant elements, hydrogen and oxygen, make up water (H₂O), the matrix of life, which forms more than 60 percent of the mass of the human body. And another key molecule, carbon dioxide (CO₂)—the ideal carrier of the carbon atom to all life on Earth—is formed from the third and fourth most abundant atoms: oxygen and carbon.

Other prominent constituents of life are also among the most abundant of elements: magnesium, sodium, calcium, iron, phosphorus, potassium, and sulfur. The overall picture conveys the powerful impression that stellar nuclear synthesis—the atom-building process in the stars—was set up from the beginning to serve the end (the purpose) of life on Earth.

It is important to stress that the selection of the atoms which enable the biochemistry of life is not because of their cosmic abundance, but because they possess the right chemical and physical properties to serve a vast number of highly specific physiological and biochemical functions in the cell.14 Carbon, for instance, possesses the right properties to build a vast diversity of chemical compounds, and this would be true even if it were not the fourth most abundant element in the universe. No other atom possesses the same fitness. In other words, the laws which determine the cosmic abundance of carbon and the other atoms of life are quite distinct from the laws that determine their fitness for life. So here is a genuine coincidence indicative of a deep biocentricity in the cosmic order: the great majority of the most abundant atoms are the most fit for life.

The Elusive Path

Despite the message of the Murchison meteorite—that the cosmos is seeded with the atoms of life and even with many of the core organic molecules, including amino acids and nucleobases—just how or where the transition from soup to cell occurred is an abiding mystery, among the greatest unsolved problems in science.

We do know that banded stromatolite formations generated by mats of bacterial cells very similar to modern blue-green algae first appear in the fossil record about 3.5 billion years ago,¹⁵ and there is some fossil and isotopic evidence which implies life might have originated as early as 3.7 billion years ago.¹⁶ So we know life has graced our planet for billions of years. But we know virtually nothing about how it originated.

The depth of the mystery is compounded by the fact that we do know, as the previous chapters in this book show, a great deal about the chemical basis of life. We have known since the early nineteenth century that the building blocks of the cell are perfectly natural chemical forms, determined by natural law. After the Murchison discovery and recent astrophysical studies, we know that at least some of these building blocks occur in vast quantities throughout the cosmos. We also know, in astounding detail, the atomic structures and molecular behavior of the key macromolecular constituents of the cell—such as DNA and RNA, proteins, and lipid membranes. We also have known since the 1960s the basic design of the cell, the meaning of the genetic code, and how information flows from the DNA into proteins. More recently, we have uncovered undreamt-of depths of complexity in the genome, including a mushrooming inventory of tiny regulatory RNAs.¹⁷

The size of standard textbooks like Molecular Biology of the Cell¹⁸ is a testimony to the vast amount of knowledge about life acquired since the 1953 discovery of the double helix (the same year Miller published the results of his famous experiment). Relevant fields outside of biology also have seen major advances, in supra-molecular chemistry for example, which have greatly expanded our knowledge of the behavior of soft matter in the mesoscopic domain.

Yet despite our extensive knowledge of the molecular biology of the cell, we remain at a complete loss as to what may have been the basic steps which led from the Murchison monomers to the cell system in terms of the known laws of chemistry and physics.

Rather than reveal the elusive path from a chemical soup to the last common ancestor of all extant life, the spectacular progress in cell biology and organic chemistry outlined above has revealed just how immense is the chasm between a soup of organic compounds and the cell with its membrane, the necessary complement of enzyme catalysts, the proteins’ synthetic apparatus, genetic information encoded in the double helix, and so forth. Despite many heroic attempts,¹⁹ no one has produced any convincing explanation of how nature could have overcome this chasm, the vastness of which was described recently by Stephen Meyer in his Signature in the Cell.²⁰ (See also Chapter 11 in my own Evolution: A Theory in Crisis²¹ and Brian Miller’s chapter in the newly revised and expanded edition of The Mystery of Life’s Origin.²²)

The origin-of-life community has identified various steps to the cell. It is widely accepted that four of these are the formation of basic building blocks such as the amino acids and nucleotides; their polymerization into proteins and DNA; the formation of the first primitive replicating system; and the evolution of the modern DNA and protein cell system with a functioning genetic code and an apparatus for protein synthesis. Only work on the first step has seen substantial progress. How the other steps were accomplished in terms of known laws of nature is a complete enigma. The widely acknowledged reality is that within the entire corpus of twenty-first century science, there is no explanation. Science, it seems, has reached an impasse. The origin of life remains as arguably the biggest unsolved problem in science.

In a critical paper summarizing this impasse, specifically with regard to the problem of how the genetic code and translation system could have emerged, Eugene Koonin and Artem Novozhilov offer the following comment:

At the heart of this problem is a dreary vicious circle: what would be the selective force behind the evolution of the extremely complex translation system before there were functional proteins? And, of course, there could be no proteins without a sufficiently effective translation system. A variety of hypotheses have been proposed in attempts to break the circle but so far none of these seems to be sufficiently coherent or enjoys sufficient support to claim the status of a real theory.²³

About proto-protein synthesizing systems that were halfway to the modern cell, they comment, “These and other theoretical approaches lack the ability to take the reconstruction of the evolutionary past beyond the complexity threshold that is required to yield functional proteins, and we must admit that concrete ways to cross that horizon are not currently known.”²⁴

^ENDNOTES

1. Francis Crick, Life Itself: Its Origin and Nature (New York: Simon and Schuster, 1981), 88.
2. “Murchison,” The Meteoritical Bulletin Database, The Meteoritical Society, May 11, 2019, accessed May 14, 2019, http://www.lpi.usra.edu/meteor/metbull.php?code=16875.
3. Keith Kvenvolden et al., “Evidence for Extraterrestrial Amino-Acids and Hydrocarbons in the Murchison Meteorite,” Nature 228 (December 5, 1970): 923–926.
4. Philippe Schmitt-Kopplin et al., “High Molecular Diversity of Extraterrestrial Organic Matter in Murchison Meteorite Revealed 40 Years after Its Fall,” PNAS 107, no. 7 (February 16, 2010): 2763–2768; Sandra Pizzarello et al., “Processing of Meteoritic Organic Materials as a Possible Analog of Early Molecular Evolution in Planetary Environments,” PNAS 110, no. 39 (September 24, 2013): 15614–15619.
5. Glycine, alanine, and glutamic acid have been identified in the Murchison meteorite. See Kvenvolden et al., “Evidence for Extraterrestrial Amino-Acids.”
6. Michael P. Callahan et al., “Carbonaceous Meteorites Contain a Wide Range of Extraterrestrial Nucleobases,” PNAS 108, no. 34 (August 23, 2011): 13995–13998; Zita Martins et al., “Extraterrestrial Nucleobases in the Murchison Meteorite,” Earth and Planetary Science Letters 270, no. 1–2 (June 2008): 130–136; Pascale Ehrenfreund and Jan Cami, “Cosmic Carbon Chemistry: From the Interstellar Medium to the Early Earth,” Cold Spring Harbor Perspectives in Biology 2, no. 12 (December 1, 2010): a002097–a002097.
7. Although an impressive inventory of basic building blocks including several amino acids, nucleic acid bases, and sugars have been synthesized abiotically, there are still several key organic building blocks, including the porphyrins and the amino acids lysine and arginine, for which no plausible prebiotic synthesis has been achieved.
8. Sun Kwok and Yong Zhang, “Mixed Aromatic-Aliphatic Organic Nanoparticles as Carriers of Unidentified Infrared Emission Features,” Nature 479, no. 7371 (November 3, 2011): 80–83.
9. Don McNaughton et al., “FT-MW and Millimeter Wave Spectroscopy of PANHs: Phenanthridine, Acridine, and 1,10-Phenanthroline,” The Astrophysical Journal 678, no. 1 (May 2008): 309–315, doi:10.1086/529430.
10. Stanley L. Miller, “A Production of Amino Acids under Possible Primitive Earth Conditions,” Science 117, no. 3046 (May 15, 1953): 528–529.
11. Eric T. Parker et al., “Primordial Synthesis of Amines and Amino Acids in a 1958 Miller H₂S-Rich Spark Discharge Experiment,” PNAS 108, no. 14 (April 5, 2011): 5526–5531.
12. For an interactive graph of the abundances, see “Abundance in the Universe of the Elements,” https://periodictable.com/Properties/A/UniverseAbundance.html.
13. Anne Marie Helmenstine, “Chemical Composition of the Human Body,” ThoughtCo., February 11, 2019, https://www.thoughtco.com/chemical-composition-of-the-human- body-603995.
14. Robert R. Crichton, Biological Inorganic Chemistry: A New Introduction to Molecular Structure and Function, 2nded. (Oxford: Elsevier Science, 2012), 4.
15. Abigail C. Allwood et al., “Controls on Development and Diversity of Early Archean Stromatolites,” PNAS 106, no. 24 (June 16, 2009): 9548–9555.
16. Guillermo Gonzalez, “What Astrobiology Teaches about the Origin of Life,” ch. 15 of The Mystery of Life’s Origin: ’e Continuing Controversy (Seattle: Discovery, 2020), 377. 17. D. P. Bartel, “Micro RNAs,” Cell 126 (2009): 215–233.
17. Bruce Alberts et al., Molecular Biology of the Cell, 4th ed. (New York: Garland Science, 2002), https://www.ncbi.nlm.nih.gov/books/NBK21054/.
18. Addy Pross and Robert Pascal, “7e Origin of Life: What We Know, What We Can Know and What We Will Never Know,” Open Biology 3, (February 11, 2013): 1–5, https://doi.org/10.1098/rsob.1...; James D. Stephenson et al., “Boron Enrichment in Martian Clay,” PloS One 8, no. 6 (2013): e64624; Eugene V. Koonin, “The Origins of Cellular Life,” Antonie van Leeuwenhoek 106 (April 23, 2014): 27–41; Eugene V. Koonin and Artem S. Novozhilov, “Origin and Evolution of the Genetic Code: 7e Universal Enigma,” IUBMB Life 61, no. 2 (February 2009): 99–111, https://doi.org/10.1002/iub.14...; Jimmy Gollihar, Matthew Levy, and Andrew D. Ellington, “Many Paths to the Origin of Life,” Science 343, no. 6168 (January 17, 2014): 259–260; Jan Spitzer, “Emergence of Life from Multicomponent Mixtures of Chemicals: The Case for Experiments with Cycling Physicochemical Gradients,” Astrobiology 13, no. 4 (April 2013): 404–413; Sara Imari Walker, P.C. W. Davies, and George F. R. Ellis, eds., From Matter to Life: Information and Causality(Cambridge, UK: Cambridge University Press, 2017).
19. Stephen C. Meyer, Signature in the Cell: DNA and the Evidence for Intelligent Design, 1st ed. (New York: HarperOne, 2009).
20. Michael Denton, Evolution: A Theory in Crisis, 1st US ed. (Bethesda, MD: Adler & Adler, 1986).
21. Brian Miller, “Thermodynamic Challenges to the Origin of Life,” in The Mystery of Life’s Origin: The Continuing Controversy (Seattle: Discovery, 2020), 359–374.
22. Koonin and Novozhilov, “Origin and Evolution of the Genetic Code.” [internal references removed]
23. Koonin and Novozhilov, “Origin and Evolution of the Genetic Code.”
24. Koonin and Novozhilov, “Origin and Evolution of the Genetic Code.” [internal references removed]

From The Miracle of the Cell by Michael Denton. Copyright © 2020. Published by Discovery Institute Press. All rights reserved. Used with permission.