Before trying
to understand the hurdles associated with the origin of life, it is useful to define life.
In its simplest terms, life is a group of chemicals that possess molecular knowledge. The
word knowledge implies that the information possessed by the chemicals is useful unlike
information which may or may not be useful. The word molecular indicates that the
knowledge resides in a chemical molecule instead of in a book or some other source.
It is this molecular knowledge that allows the chemicals in life to
maintain a state that is very different from nonliving chemicals like vinegar, ammonia,
and water. The molecular knowledge that life possesses is both procedural and conditional.
Procedural knowledge is knowledge about how to do something. For example, how to extract
energy from a sugar molecule, and use it to build something else. Conditional knowledge is
knowledge about why and when something needs to be done. For example, when there is no
sugar present certain metabolic pathways need to be turned off. Conditional knowledge in
molecules is similar to that found in computer programs. A computer program may execute
one command if a certain condition is true, and another command if the condition is false.
Computers do not think. The decisions are predetermined by the logic used in the computer
code.
It is now possible to develop a concise and accurate definition for
life: Life is a system of chemicals possessing molecular knowledge and a mechanism to
implement this knowledge in such a way that the system can survive long enough to
replicate itself.
Today, life requires several chemicals to survive, grow, and reproduce.
Two chemicals, DNA and RNA, store the required knowledge. Proteins and to lesser extent
RNA implement this knowledge, and a third chemical ATP provides the energy to power the
implementation. At a minimum, the simplest living system must be able to perform three
critical functions:
• Store molecular knowledge.
• Implement this knowledge.
• Tap a plentiful energy source to power the implementation.
Herein, lies the mystery behind life’s origin. The origin of life
is a classic example of the chicken or the egg paradox because none of the critical
functions listed above can exist without the others.
Many investigators have tried to overcome the paradox by suggesting
that the first living thing was a single chemical that contained both the knowledge and
the ability to implement the knowledge. RNA is a natural choice for the first living
chemical because it can both store and implement knowledge. Nevertheless, after 25 years
of experiments, the RNA hypothesis has yet to live up to its expectations. RNA has quite a
bit of trouble with self replication (see Joyce:1989 and chapter 10).
Investigators have for the most part ignored the third critical
function required for life, the need to tap an energy source to drive replication. Without
this function, self replicating molecules become a special type of perpetual motion
machine. A perpetual motion machine is a machine that runs forever with no energy input.
Perpetual motion machines do not exist. They may run for a short time, but without a
continuous input of energy, they eventually stop. Furthermore, all machines must know how
to tap an energy source. A car with an empty gas tank cannot be driven to the gas station
just because the sun is out. The sun provides an almost unlimited source of energy, but a
gas engine does not know how to convert this energy into work. The same constraints apply
to a self replicating RNA molecule. Unless such a molecule knows how to tap a plentiful
energy source to drive its own replication, it can only exist in text books and in the
imagination of researchers.
To summarize, life requires some minimal molecular knowledge to
replicate. This knowledge can be possessed by a single chemical, or it can be spread out
among many. In either case, the system must possess the knowledge to replicate, a way to
implement this knowledge, and a way to power the implementation. A system that does not
possess all three is not a living system.
Figure 2 depicts the focus of this book. The focus is not on whether or
not a man can evolve from an ape. Instead, the following chapters will concentrate on the
genes and proteins that were required for the origin of life and on the chemicals that
gave rise to these first genes and proteins. These are events that happened more than 2
billion years ago.
The reason for doing this is simple. If a new gene evolves early in
life’s history, and it is completely different from any other existing gene, then the
possibility that it arose by gene duplication can be eliminated. This makes the analysis
much more manageable. Furthermore, the techniques used in the book simply will not work to
prove that man did not evolve from apes. The DNA in a chimpanzee is almost identical to
that of man’s DNA. This similarity makes it impossible to infer design.
In figure 2, the self replicating molecule leads to a perpetual motion
machine. The car in this figure that is pulled along by the powerful magnet is just one
example of such a machine. Since perpetual motion machines do not exist, this pathway is
not a very promising solution to the mystery of life’s origin. It is far more likely
that life arose all at once.
The difficulties associated with chemical evolution suggest that the
biological precursors necessary for life would have been scarce if they existed at all,
and this scarcity suggests that the first living thing was able to synthesize all of the
chemicals that it needed for replication and drive this synthesis with a plentiful energy
source. Today, life can only tap plentiful energy sources with the help of proteins and
lipids, and this suggests that the first living thing was probably also able to synthesize
proteins and lipids. Therefore, the first living thing was not a simple self replicating
chemical, but rather a living cell very similar to life as it exists today.
While the idea that life arose all at once is not a popular one as it
is contrary to Darwinian evolution, there is certainly quite a bit of evidence to suggest
that it did.
Notice in figure 2 that the Cambrian explosion may also imply design
(Meyer: 2005). The fossil record indicates that almost every major biological
classification (phylum) arose in a very short time span about 500 million years ago. The
question mark is meant to show that any design inference based on the Cambrian explosion
is subjective because no scientist has yet to accurately model the probabilities of such
an event.
Figure 2: The History of Evolution
Before proceeding, one final clarification is in order. A few people
have intentionally confused creation science with intelligent design. Creation scientists
believe that the creation story in Genesis is scientifically accurate. Intelligent design
differs from creation science in several important ways. First, intelligent design makes
no assumptions as to what the scientific data should show. Intelligent design is just a
methodology that uses indirect logic to interpret the scientific evidence. It does not
depend on religion. Furthermore, the statistical techniques used by intelligent design
require an old earth, common ancestry, and descent with modification.
References:
1) Richard Dawkins, The Blind Watchmaker, Norton and Company, 1996.
2) Fox, Dose, Molecular Evolution and the Origin of Life, Freeman and Company, 1972.
3) Shapiro, “The Prebiotic Role of Adenine: A Critical Analysis”, Origins of
Life and the Evolution of the Biosphere, 25: 83-98, 1995.
4) Thaxton, Bradley, Olsen, The Mystery of Life’s Origin: Reassessing Current
Theories, Philosophical Library, 1984.
5) Levy, Miller, “The Stability of the RNA bases: Implications for the Origin of
Life,” 95: 7933-7938, PNAS, 1998.
6) Shapiro, “Prebiotic Cytosine Synthesis: A Critical Analysis and Implications for
the Origin of Life,” 96: 4396-4401, PNAS, 1999.
7) Larralde, Robertson, Miller, “Rates of decomposition of Ribose and other Sugars:
Implications for chemical Evolution,” 92:8158-8160, PNAS, 1995.
8) Joyce, Schwartz, Miller, Orgel, “The Case for an Ancestral Genetic System
Involving Simple Analogues of the Nucleotides,” PNAS, 84:4398-4402, 1987.
9) Joyce and Orgel, The RNA World, Gesteland, Cech, Atkins, Cold Spring Harbor,
“Prospects for Understanding the Origins of the RNA World,” 1999. 10) Ohno,
Evolution by Gene Duplication, Springer Verlag, 1970.
11) Fuller, Sanchez, Orgel, “Solid state Synthesis of Purine Nucleotides,”
Journal of Molecular Evolution, 1975.
12) Meyer, “The Origin of Biological Information and the Higher Taxonomic
Categories,” Proc. of the Biological Society of Washington, 117: 213-239, 2005.
13) Miller, “Which Organic Compounds Could Have Occurred on the Prebiotic
Earth?”, Cold Spring Harbor Symposia on Quantitative Biology, Volume L11, 17-25,
1987.
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