One of the greatest enigmas of our existence is our very existence. It is therefore no surprise that biologists and biochemists are researching abiogenesis, the chemistry and mechanisms that created the first life forms. This research plays into the ongoing debate between Darwin’s Theory of Evolution, Creationism, and Intelligent Design. Creationism represents the Christian belief that God created all forms of life. Intelligent Design is the hypothesis that various aspects of the formation of the universe and the evolution of life are best explained by a higher intelligence, not by natural processes. It further is an attempt to reconcile the things that science cannot explain. This article examines science’s attempt to understand the genesis of life as compared to the Intelligent Design argument, especially with respect to DNA, the amazing and complex genetic material found in living things.
Based on the ratio of carbon isotopes in ancient rocks, life was in existence 3.85 billion years ago, when the Earth was only 700 million years old. Charles Darwin himself did not speculate on how the first life forms emerged on early Earth as he believed it was a great mystery: “It is mere rubbish to talk about the origin of life; one might as well talk about the origin of matter.” [1] Since the days of Darwin, scientists have been seeking answers to the genesis of life. The search for answers has been elusive and Intelligent Design advocates are quick to use this as support for their arguments.
One argument is the concept of “irreducible complexity,” defined by Michael Behe as “a single system which is composed of several interacting parts that contribute to the basic function, and where the removal of any one of the parts causes the system to effectively cease functioning.” [2] Intelligent Design advocates argue that DNA is irreducibly complex; therefore it could not have originated from a random process. [3,4] DNA contains four different nucleobases: A (adenine), C (cytosine), T (thymine) and G (guanine), which are purposefully arranged within the molecule in the form of genes. These genetic instructions according to Dr. Stephen Meyer are a language similar to computer code, and he further notes that even the simplest bacteria have a complex genetic code. [5] Quoting Werner Gitt, professor of information systems:
"The basic flaw of all evolutionary views is the origin of the information in living beings. It has never been shown that a coding system and semantic information could originate by itself . . . The information theorems predict that this will never be possible. A purely material origin of life is thus [ruled out].” [6]
Abiogenesis skeptics also cite other factors. [7] Proteins that may spontaneously form from amino acids would break down in water due to hydrolysis and they would also be susceptible to destruction from UV radiation, which was much stronger in primordial times. They would also be susceptible to oxidation, although scientists believe that little oxygen was present in the atmosphere at that time. Other organic molecules would potentially suffer the same fate.
The two defining properties that separate life from non-living matter are metabolism (processing raw materials for the purpose of sustaining the organism) and reproduction. The challenge for science is to arrive at life the first life forms from a lifeless pool of chemicals. Scientists have demonstrated that amino acids (precursors to proteins), nucleobases (precursors to RNA and DNA), and numerous other organic chemicals are easily formed under the conditions of early Earth. Numerous organic compounds have additionally been discovered in outer space and it is possible that some of these compounds may have contributed to the genesis of life. [8]
In order to form more complicated molecules, sources of energy are required. This was not an issue in the early days of Earth: ultraviolet radiation, geothermal energy, lightning, and solar heat were readily available. [9] Condensation reactions (reactions that produce water) are used in order to make more complicated molecules from the simpler chemicals. These reactions would be unfavorable in the open ocean, but could easily occur in tidal pools, where concentration would occur due to evaporation. In addition, clays, pumices, and micropores in rocks were believed to participate in the synthesis of complex organic molecules by forming templates. [10] Some sort of restrictive membrane simulating the modern cell membrane would be advantageous in that it would protect more delicate molecules supporting life. Certain proteins and other simple organic compounds will form barriers similar to cell membranes. [11]
A thorough and especially animated synopsis of the genesis of life is offered on the website http://www.evolutionofdna.com. [12] Here, the author suggests that amino acids and aromatic compounds similar to nucleobases are concentrated in tiny pools along tidal areas. In a select few pools, the right chemicals were present and polymerized into a specific aromatic chain and a protein that could read the aromatic chain in order to replicate itself. Through chemical evolution, other proteins resulted that were capable of reproducing themselves or their parent aromatic chains, leading to a fully “self-replicating” chemical system. Evolution would be accelerated by the enormous number of micropools available on the shoreline. Eventually, proteins would evolve that would manufacture proteins and aromatic chains from simple raw materials (metabolism) and structural proteins would evolve that would hold everything together. The result would be the first life form, named “Cassius” by the author. Cassius would develop the ability to manage energy, perhaps by employing adenosine phosphates which are used to store and deliver energy in modern life forms. At some point in the evolutionary process, Cassius would incorporate a cell membrane in order to protect it against hostile environments.
The elegance of this hypothesis is that the author relies on simple proteins and aromatic polymers to drive the prebiotic evolutionary process. The author admits that it would take a considerable amount of luck for this system to develop, especially at the very beginning. The odds for the right chemicals to all be in the same place at the same time with the right degree of polymerization would have been extremely remote, but the author believes that the enormous number of micropools and the time scales involved would improve the odds: “There are quite a few steps to the transformation, but none of them are sufficiently improbable that they would have taken billions of years.” [13]
Up to this point, the author had not defined the chemistry of the aromatic chains, essentially the first genes, only suggesting that they would be far simpler than modern RNA. The author proposes that early in the evolution of Cassius, complimentary base paring develops. Base paring would provide a major advantage in that it would facilitate enzyme production and organization of the aromatic chains. Base paring also would make it especially easy to replicate the genetic material when the organism develops cell division. It is speculated that through base paring, RNA would eventually evolve. The subsequent jump from RNA to DNA is not a large jump, and may have been driven by the organism needing to preserve the molecules holding the genetic code, whereas the RNA molecules doing the actual daily work could be digested once their work was complete. The author proposes that through evolution, the organism learned to convert the ribose molecule to deoxyribose, the sugar component of DNA. DNA would be more stable and have stiffer chains than RNA, so they would be easier to read. At first, DNA would be single-strand until evolution developed the famous double-helix structure.
This explanation of the emergence of DNA is vague and does not explain a step-by-step process from a pool of simple chemicals to an elaborate genetic language. Even the simplest bacterium has DNA containing 600,000 base pairs. [14] Spontaneous formation of this type of a molecule is essentially impossible. However, somewhere between 10 and 50 amino acids form modern protein based enzymes. The very first self-replicating protein likely was in this size range. [15] The assembly of a specific 10 component protein from 20 different amino acids, although still infinitesimal at about one chance in ten trillion, is much more likely, especially given the trillions of available micropools and millions of years of trial and error. Simple aromatic chains of the same length would have a comparable probability of existence. If simple proteins and aromatic chains would evolve into the primitive life form Cassius, it is plausible that the aromatic chains could evolve into RNA with simple coding, then into DNA with a genetic language pieced together by segments of RNA.
Admittedly this is a tortuous path to the emergence of life. It is much easier to jump to the conclusion that God created life given that science has not presented a concrete answer. However, the route proposed by the evolutionofdna.com author seems plausible and it is conceivable that life evolved directly from inorganic chemicals without super-intelligent influence. As science advances, those studying abiogenesis will continue to unravel the mystery of the genesis of life and may even learn how to create a living entity out of a mixture of chemicals. If they succeed, that in no way proves that a Higher Power does not exist. The very fabric of the Universe is mysterious and the fact that lifeless matter may be assembled into a living being is amazing, regardless of the route. There is room in the Universe for both science and God. Quoting Albert Einstein: “A knowledge of the existence of something we cannot penetrate, of the manifestations of the profoundest reason and the most radiant beauty - it is this knowledge and this emotion that constitute the truly religious attitude; in this sense, and in this alone, I am a deeply religious man.” [16]
References:
5. See 3.
6. See 3.
9 Ibid.
10. Author unknown, http://www.evolutionofdna.com/
11. See 8.
12. See 10.
13. See 10.
14. See 10.
15. See 10.
Photo credit: wikipedia.com
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