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 haldanes 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.”
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 datenot 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 intermolecularinteractions, 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’.