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Why Re-Invent the Crystal?

Reports of the National Center for Science Education
Title: 
Why Re-Invent the Crystal?
Author(s): 
Gary Hurd
Volume: 
28
Issue: 
5–6
Year: 
2008
Date: 
September–December
Page(s): 
54–55
This version might differ slightly from the print publication.

Creationists attack the question of the origin of life because few scientists are sufficiently familiar with the current research to explain it. The movie Expelled further obscured the issue by dishonest reporting.

The contribution of inorganic crystals to the formation of complex organic molecules has been an important part of origin-of-life research for over four decades. When interviewed by Ben Stein, Michael Ruse said that life could have originated by molecules binding to crystals. The scene cuts to an old movie clip of a fortune-teller with a crystal ball, and Stein has a sneering laugh at Ruse’s expense. The derision heaped on the idea that crystals contributed to the origin of life is an excellent example of scientific ignorance’s being exploited by the producers of Expelled.

The role of crystalline minerals in the origin of life was proposed by JD Bernal over forty years ago. Bernal, following Aharon Katchalsky, pointed out that the clay montmorillonite’s surface readily bound simple organic molecules (Bernal 1967). Most clays are plate- or lath-shaped micro-crystals made of silicon, oxygen, and aluminum, interspersed with other elements (commonly iron, calcium, or sodium) which can replace the major elements. These substituted metals alter the electric charge on the crystal’s surface, providing locations where organic molecules can attach. The structure of the clay crystal provides stability and organization essential for the origin of life (for example, Wang and Ferris 2005; Hanczyc and others 2003; Saladino and others 2002).

Leslie Orgel (1973) coined the now famous term “specified complexity” to distinguish between crystals, which are organized but not complex, and life, which is both organized and complex. He was well aware then of the potential role of crystalline minerals in the origin of life. Twenty-five years later, Orgel demonstrated the thermodynamic favorability of polymer formation on grains of the mineral apatite, or hydroxylcalcium phosphate (see Ferris 2002 for a “reader-friendly” account).

Consider for a moment: our teeth contain calcite — a crystal of calcium carbonate. Our bones are made from calcite, and marine shells are made from calcite coupled with aragonite (both crystals). Those bones and our teeth also need another crystal: apatite, or hydroxylcalcium phosphate. Marine shells are made from calcite and aragonite (both crystals). Plants, particularly grasses, need silicon crystals called phytoliths to exist. The bodies of diatoms are mostly crystal silicon. Silicon or calcium crystals are found in nearly all life on earth. Crystals made of iron oxide (magnetite [Fe3O4]) or its sulfide counterpart (griegite [Fe3S4]) are found in many life forms on earth, from bacteria to vertebrates — including humans. These crystals are chemically indistinguishable from those formed abiotically — that is, produced entirely from the normal actions of physical processes on earth without any input by a living organism. Since we must have crystals to live at all, it is only reasonable to ask what role crystals may have played in the origin of life.

Studies of pre-biotic chemistry shows that interactions between mineral crystals and naturally occurring molecules leads to increased complexity, and more abundant yields from abiotic synthesis. Here again we see an important role for the mineral calcite. Robert Hazen has studied the binding of amino acids to surface of calcite crystals and discovered that they are aligned in a way that favors one structural form — the “left-handed” isomer — over others (Hazen 2005; Hazen and others 2001). The isolation of these amino acids was an important step in the origin of life (the “bias” of life for left-handed forms when the laws of physics would predict equal proportions of right- and left-handed forms is a strident creationist objection to most origin-of-life scenarios). Crystals in another group, the borates, stabilize the naturally forming sugar ribose, which is an important molecule needed to form the cellular workhorse RNA (Ricardo and others 2004).

Finally, the most common creationist objections to origin of life research is the insistence that the famous Miller-Urey experiment was a failure. This 1953 experiment was the first to demonstrate that a simple energy source, an electrical spark, could induce the spontaneous formation of amino acids from a mixture of gases. Creationists from the Discovery Institute to the young-earth creationists of Answers in Genesis all claim that the gases used by Miller could not have been found on the early earth. Whether or not this objection is true, Stanley Miller’s last paper (published posthumously in 2008) demonstrated that the presence of the crystal calcite and the iron crystal pyrite in the preparation leads to high yields of amino acids even from neutral gas mixtures (Cleaves and others 2008).

Are there traces of these ancient events found today? Yes, as evolutionary theory suggests that there must be. We see that inorganic crystals common in the ancient earth are part of all living things. First of all, we remember that these “complex” minerals found in living organisms are in fact mostly identical to the inorganic crystals we find in rocks today; biominerals are merely smaller. We also see that all living things — from bacteria to mammals — utilize chemical reactions and pathways that interact with these crystals. There are numerous enzymes and proteins that are part of a cell’s chemistry that operate to build up or break down these crystals.

One example found in all vertebrates is osteocalcin. Recent research related osteocalcin to other vitamin K-dependent proteins that control calcium metabolism, including in bacteria (Berkner 2005). Finding this enzyme in bacteria confirms that the use of dissolved minerals and crystal surfaces was a part of the earliest forms of life on earth — and one that has been maintained and passed along to successive branches in the tree of life.

Is it then silly, or irrational, to think that these essential crystals were part of the origin of life? Not at all! Only the ignorant will be fooled by the derisive scoffing of Stein in his propaganda movie into thinking that Ruse’s comments were just grasping at straws to avoid a theistic solution to life’s origin. While the exact relationship of crystalline minerals to the first complex organic molecules is incompletely understood, it is an active and productive area of scientific research — in stark contrast to the sterility of “intelligent design” creationism.

References

Berkner KL. 2005. The Vitamin K–dependent carboxylase. Annual Review of Nutrition 25: 127–49.

Bernal JD. 1967. The Origin of Life. London: Weidenfeld & Nicholson, 1967.

Cleaves HJ, Chalmers JH, Lazcano A, Miller SL, Bada JL. 2008.A reassessment of prebiotic organic synthesis in neutral planetary atmospheres. Origins of Life and Evolution of Biospheres 38 (2): 105–15.

Ferris JP. 2002. From building blocks to the polymers of life. In: Schopf JW, editor. Life’s Origin. Berkeley, University of California Press. p 113–39.

Hanczyc MM, Fujikawa SM, Szostak JW. 2003. Experimental models of primitive cellular compartments: encapsulation, growth, and division. Science 302: 618–22.

Hazen RM. 2005. Genesis: The Scientific Quest for Life’s Origin. Washington (DC): Joseph Henry Press.

Hazen RM, Filley TR, Goodfriend GA. 2001. Selective adsorption of L- and D-amino acids on calcite: Implications for biochemical homochirality. Proceedings of the National Academy of Sciences USA 98 (10): 5487–90.

Orgel L. 1973 The Origins of Life: Molecules and Natural Selection. New York: John Wiley and Sons.

Ricardo A, Carrigan MA, Olcott AN, Benner SA. 2004. Borate minerals stabilize ribose. Science 303: 196.

Saladino R, Crestini C, Ciambecchini U, Ciciriello F, Costanzo G, Di Mauro E. 2004. Synthesis and degradation of nucleobases and nucleic acids by formamide in the presence of montmorillonites. ChemBioChem 5 (11): 1558–66.

Wang KJ, Ferris JP. 2005. Catalysis and selectivity in prebiotic synthesis: initiation of the formation of oligo(U)s on montmorillonite clay by adenosine-5’-methylphosphate. Origins of Life and Evolution of Biospheres 35 (3): 187–212.

Additional reading

Deamer DW. 1997. The first living systems — a bioenergetic perspective. Microbiology and Molecular Biology Reviews 61 (2): 239–61.

Fry I. 2000. The Emergence of Life on Earth: A Historical and Scientific Overview. New Brunswick (NJ): Rutgers University Press.

Schopf J, editor. 2002. Life’s Origin: The Beginnings of Biological Evolution. Berkeley: University of California Press.

Smith JV. 1998. Biochemical evolution. I. Polymerization on internal, organophilic silica surfaces of dealuminated zeolites and feldspars. Proceedings of the National Academy of Sciences USA 95 (7): 3370–5.

Smith JV, Arnold FP, Parsons I, Lee MR. 1999. Biochemical evolution III: Polymerization on organophilic silica-rich surfaces, crystal-chemical modeling, formation of first cells, and geological clues. Proceedings of the National Academy of Sciences USA 96 (7): 3479–85.

About the Author(s): 
Gary Hurd
c/o NCSE
PO Box 9477
Berkeley CA 94709-0477
ncseoffice@ncseweb.org

Gary Hurd received a doctorate in social science (emphasis in anthropology) from the University of California, Irvine, in 1976. He was a medical researcher and professor of psychiatry at the Medical College of Georgia in 1986 for ten years before returning full-time to archaeology. He became active in resisting the creationist attack on education working at a small natural history museum. His contributed chapter to Why Intelligent Design Fails (edited by Matt Young and Taner Edis; New Brunswick [NJ]: Rutgers University Press, 2004) was cited in the decision in Kitzmiller v Dover.