Whether Or Not Prebiotic
Soup Was Ever Needed/Existed For Origin of Life
Summary: For most of modern theories of Origin
of Life, Prebiotic Soup is the starting point and much of the research is
focused on this point. However till date not an iota of evidence has been
detected in support of existence of Prebiotic Soup at any time in the history
of Earth. It is concluded that Prebiotic Soup was neither needed nor existed
for Origin of Life on Earth.
Darwin suggested that life could have begun in
a warm little pond with all sorts of ammonia and phosphoric salts, light, heat,
electricity present that a protein was formed ready to undergo still more
complex changes. At the present day such matter would be instantly devoured or
absorbed which would not have been the case before living creatures were
formed.
This
gave rise to Primordial Soup Theory which suggests that life began in a pond or
ocean as a result of the chemicals from the atmosphere and some form of energy
to make amino acids; the building blocks of proteins, which would then evolve
into all the species. This is supposed to happen at least 3.8 billion to 3.55
billion years ago.
This involves kaleidoscopic or random
permutation and combination of chemicals with eventual selection and
accumulation of useful permutations and combinations of chemicals so as to
eventually give rise to origin as well as evolution of life.
Alexander Oparin in 1924 suggested the idea of
Prebiotic Soup and today this is the starting point for most of modern theories
of Origin of Life. Around the same time J.B.S. Haldane suggested that Earth’s
Prebiotic oceans are different from today’s oceans – would have formed a hot
dilute soup in which organic compounds could have formed. The underlying hypothesis held by Oparin and Haldane was that
conditions on the primeval Earth favored chemical reactions that synthesized organic
compounds from inorganic precursors. Arguing along the same line it has been speculated that once upon a
time there existed organic matter on Earth in sufficient concentration that its
spontaneous, kaleidoscopic random interactions ultimately led to Origin of
Life. The principal difficulty with this line of thinking is lack of
specificity of organic chemical reactions. This is quite unlike chemistry of
life i.e. Biochemistry.
Biochemist Robert Shapiro has summarized
the "primordial soup" theory of Oparin and Haldane in its "mature
form" as follows
1. The
early Earth had a chemically reducing atmosphere.
2. This
atmosphere, exposed to energy in various forms, produced simple organic
compounds ("monomers").
3. These
compounds accumulated in a "soup", which may have been concentrated
at various locations (shorelines, oceanic vents etc.).
4. By
further transformation, more complex organic polymers – and ultimately
life – developed in the soup.
While
steps 1-3 have been basically observed experimentally, step 4 has been criticized
as simplistic - a stage of "then magic happens".
However
even existence of chemically reducing atmosphere of Early earth has been
doubted by geochemists. To quote:
“But is the “prebiotic soup” theory a
reasonable explanation for the emergence of life? Contemporary geoscientists
tend to doubt that the primitive atmosphere had the highly reducing composition
used by Miller in 1953.” http://www.sciencemag.org/content/300/5620/745.full
Even need for step 3 is doubtful since
Biological systems show extraordinary capacity to operate under very-very low
concentrations of essential chemicals coupled with ability to concentrate
essential chemicals as per the requirements of particular Biological Systems.
Since 1924, much
work has been done to gather evidence in support of Primordial Soup Theory but
till date not an iota of
evidence has been discovered supporting Prebiotic Soup hypothesis or existence
of Prebiotic Soup.
What has generally been overlooked by
scientific community till date is the fact that Biochemistry or Chemistry of
life is unique and distinctive to living state. It is totally devoid of
randomness. Rather, Biological Systems in order to keep existence can’t permit
random chemical reactions. Some of the salient features of Biochemistry are:
(I)
Specificity,
accuracy and precision of reactions — unlike
organic chemistry in which a large number of side reactions invariably occur
during any organic reaction leading to formation of side products, in
biochemistry reactions are highly specific, precise and accurate without any
side reactions and free from side products. This is essential to avoid chaos in
animate matter.
(II)
In
biochemistry, all reactions take place under conditions of existence of given
organism or conditions of its internal milieu which are often quite different
from conditions in which similar inorganic and organic reactions proceed.
Rationally speaking biochemical reactions must have originated under the
conditions in which relevant organisms are usually found. Because of vast
variation in habitat of organisms, the same potentiality is realized through
differently structured enzymes effective under different conditions. Therefore, for evolution of Biochemistry,
environment has never been an absolute constraint.
(III)
Biochemistry is deterministic. Deterministic character of chemistry of life is
well exhibited by its properties such as specificity of intermolecular interactions, chemo selectivity, homochirality,
stereo- specificity of biological molecules. Even the subsequent course of
events has been essentially deterministic with a strong propensity to stabilization,
fixation, preservation and propagation of useful past and present innovations.
Biochemistry may have its roots in stochastic inanimate interaction of matter
and energy but stochastic organic chemical reactions can’t account for
specificity of reactions seen in biochemistry. Unfolding or evolution of
biochemistry requires a surprising lack of side reactions (Smith and Morowitz).
How this extraordinary specificity of chemical reactions is achieved in the
absence of genes giving rise to catalytic polymers with three dimensional
substrate pockets is still a matter of conjecture and contemplation.
So the key questions which we must address
ourselves keeping in view homochirality of biological molecules are:
(i)
Why
homochirality is so essential that it is a deterministic trait in entire
biosphere or operates as a matter of law. Does it imply some constraints of
molecular intelligence?
(ii)
How this
deterministic homochirality was obtained and sustained, may be from a
stochastic beginning and in a stochastic world? The answer to this might be
simulation and induction, directed by utility.
All the experimental evidence gathered so far
to bridge the gap between inanimate matter and animate matter belong to the
realm of stochastic chemistry and the reaction products are devoid of life like
intelligent molecular activity. This statement is applicable to both, abiotic
monomer synthesis as well as abiotic polymer synthesis.
Time line of origin of
life shows that it must have taken at least 200 Ma after formation of earth
crust and oceans for life to appear. Life might have begun in the form of
fossilized Cyanobacteria in Stomatolites which are known to occur as early as
3.85 Ga. Any theory of origin of life should be able to explain time involved
in its origin. Therefore various experiments demonstrating synthesis of
monomers over a very short period of time fail to explain as to why the time
involved in origin of life was of the ~ 200 Ma. Hence, by whatever mechanisms
life originated, it must have been very slow and cumulative over a period of
time. Therefore the vast amount of experimental evidence only lends credibility
to our belief in abiogenesis and that one day it shall be possible to provide
detailed explanation of origin of life from inanimate matter but the
accumulated evidence is otherwise not sufficient to explain phenomenon of
origin of life. Considering the enormous time involved, processes leading to
origin of life must be time dependent, extremely lengthy, cumulative, complex
and intricate which at the same time are relatively stable, capable of
fixation, preservation and propagation so that advances made are cumulative
ultimately leading to origin of life. The process of origin of life should have
proceeded through accumulation of a series of small discrete steps giving
semblance of gradualism and continuity. Easy switching between inanimate
behavior and life like activity should have been widely rampant in very-very
early stages of origin of life. Vast distribution of life on earth shows that
constraints like U.V. Radiation, Toxic effects of atmospheric oxygen against origin of life are just
scientific fictions, since a large number of forms that could exist have
evolved only after successfully meeting those constraints. Hence, these
constraints, even though may be valid are not absolute or non-negotiable.
Origin of life must involve origin of ways and means to circumvent and
negotiate these constraints or to tolerate these constraints.
Therefore, life like activity began on earth at any point of time in
its history when earth was capable of supporting or inducing life like activity
due to some unknown cause-effect sequences. All kinds of life like activity
began independent of each other wherever a source of energy, little moisture
and relevant chemical elements were available even if in very-very minute
amounts. Considering ubiquity of life on earth, environmental conditions could
not have been a major deterrent. Rather they influenced type of life and life
like activity to which every other type of life and life like activity has a
relationship of adaptation and adaptability or harmony. Therefore, all life
forms originated in such a way that they were ab initio adapted to conditions of their existence. Time and place
has played a more significant role in determining type of life like activity
and type of life through yet unknown cause-effect sequences. This is in
conformity with time dependent increase in complexity of life on earth as per
fossil records and place dependent biodiversity. Even Darwin observed that
biodiversity on Galapagos Islands varied according to some geographical rule.
Summarizing all above, for Origin of Life neither Prebiotic Soup was
ever needed nor could have ever existed. This is in conformity with all the
experimental evidence gathered till date.
Author: Dr Mahesh C. Jain is a practicing
medical doctor and has written the book “Encounter of Science with Philosophy –
A synthetic view”. The book begins with first chapter devoted to scientifically
valid concept of God and then explains cosmic phenomena right from origin of
nature and universe up to origin of life and evolution of man. The book
includes several chapters devoted to auxiliary concepts and social sciences as
corollaries to the concept of God. This is the only book which deals with
origin of nature and universe from null. Twenty-ninth chapter of the book deals
with the subject matter of ‘Origin of Life’.
http://www.sciencengod.com/buynow.php
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