Identifying the origin of biological information in the origin of life on earth is admittedly fundamental and most complex problem of biology, even today. The hints of the enormous problem are available from the investigations of uniqueness of information, mutually dependent nature of cell components, functional capability and functional characteristics of a living cell.
Features of a Living Cell
Let us first consider the functional characteristics of a living cell. Molecular biologists admit that each cell consists of artificial language and decoding system, memory bank for information storage and a control system regulating assembly of components. The cell structure is also characterized by safe proof reading devices for quality control and capable of replicating its entire structure within a few hours. The characteristics indicate a nanotechnology active inside a cell which weighs less than a few thousand of millionths of a gram even for a human cell. Contextually, it may be mentioned, that a human DNA can still store up to 750 megabytes of information which is not less than 35,000 pages in Microsoft word in text form without any image.
Secondly, mutually dependent behavior of cell components require several well-matched interacting components to contribute to cell functions, wherein removal of any of the components causes the system to stop functioning. The functional capability of a cell is no less amazing. From reproduction to repairing of a broken bone happens down the cellular level. Specialized cells make enamel for our teeth or the clear lenses in our eyes and cells determine traits of organism including color of hair/eyes.
But the most debated specialty of the cell-story revolves round the uniqueness of information of a living cell. The functionally alphabetic character of the four nucleotide bases in DNA indicates information carrying capacity of nucleotides. Again, amino acid sequencing to functional proteins are observed to be so irregular that the transmitted information becomes complex (or improbable). But it does not fully reveal all about information that exists in a living cell. Molecular biologists have recognized that sequence of nucleotides and amino acids in the functioning bio molecules posses a high degree of specificity or meaning. So, the precise determining of sequence of bases in the nucleic acid is an additional property of information present in a living cell. In short, a living cell not only carries complex information but also precisely determines its sequence and this complex specificity is absolutely necessary to transmit heredity and maintain all biological functions of a cell.
Biological information, as described above, from the view points of molecular biologists has thrown a challenge to life-researchers to explain the origin of information in the origin of life.
Early Atmospheric Condition and the Primitive Living cell
The earliest fossil of a prokaryote cell discovered is said to be 3.5 billion years old. What exactly was the earth's atmosphere at that time is debatable today. But, what is certain that it was different from the present atmospheric conditions of earth. Still, what is to be noted here is that there is hardly any basic difference between the most primitive living cell and a cell of a modern organism. The same basic quality of information exists in a bacteria cell or in a eukaryote cell of a human. A prokaryote bacteria cell has a shorter genetic code, but it gives instructions as precisely as that of human cell. Thus, the first living cell had to possess a cell wall, the ability to process "food" to create energy, the ability to expand and ability to split itself to reproduce.
Early Theories about Emergence of Life and their Limitations
Now, there are basically two schools of naturalistic explanations about how life started on earth. One type of explanation is chance-based and the other hypothesis is based on self-organizational laws of chemical attraction due to necessities or properties of the components of a cell. Other explanations like pre-biotic natural selections, are either extension of the two hypotheses or not important enough in the context of the origin of life.
The most common explanation about the origin of life is that it happened by chance over a very long period of time. In an extremely favorable pre-biotic condition, the theory envisions, a series of random chemical reactions became more and more complex over time and led to formation of a living cell gradually and naturalistically from chemical precursors.
But, this explanation of the origin of life seems almost impossible on various counts. From the calculations of probability theory, we find that, the probability of building a 100 amino acid length chain, in which all bonds are peptide bonds and all amino acids are left-handed, is roughly 1 chance in 10^60. Again, by random process, the probability of constructing a short functional protein is no more than 1 chance in 10^125. It means if tried at the rate of 100 billion a second (Or 100 billion attempts take place per second to construct a short protein), it would take longer than the age of the universe. Further, the pre-biotic natural selection, which is indistinguishable from the chance-based hypothesis, presupposes self-replication ignoring the fact that self-replication requires functioning nucleic acids and proteins.
Thus, from the view point of mathematical probability and also due to inherent self-contradictions of the chance based hypothesis, it is eliminated as an explanation for the origin of life on earth.
Another school of naturalistic theories to explain how life emerged on earth look for self-organization laws and properties of chemical attraction (Necessity Principle). It is proposed that deterministic forces made the origin of life "inevitable" either by "differential bonding affinities" or by "self-ordering properties" of chemical attraction. According to some exponents of the school of thought life is "biochemically predestined" by the properties of attraction that exist among its constituent chemical components.
But, in the absence of any bond between bases along the information-bearing axis of DNA and any differential affinities between the backbone and the specific bases, the theory is unable to explain sequentially specific arrangement of nucleotide bases in DNA.
The same reasoning is applicable for RNA molecules thereby reject the RNA WORLD hypothesis to solve the sequencing problem. It is also observed that to the extent the forces of attraction between constituents in a sequence determine the arrangement of the sequence, to that extent the information carrying capacity of the system is diminished. So, the idea of differential affinities actually reduces the information carrying capacity of a living cell.
Again the "self-ordering properties" arguments cannot solve the problem since the properties of biological building blocks do not determine the arrangement of functional polymers. Nucleotide bases are indifferent to how they are arranged. Thus, the properties of the constituents remain largely indifferent to the sequences that they may adopt. Hence, as against "self-ordering" principle, properties of nucleotide bases and amino acids do not make any specific sequence 'inevitable'.
In the context of limitations of 'chance-based' chemical evolution and 'necessity-based' self-organization theories to explain origin of information, some people argue that in future we may discover a very particular set of initial conditions that will solve the problem of sequence specificity. However, unfortunately, this hypothetical statement seems to seek such initial conditions which accommodate a precise and meaningful sequence full of information. So, the problem of finding the initial information remains unanswered. Again, scientific laws, as know them, usually describe predictable relationship between antecedent conditions and successive events. So, scientific laws appear insufficient to explain highly uncertain but specified sequences (antecedent) of information in a living cell that make biological functions (successive events) possible.
Intelligence as Acceptable Source of Information
In the context of the above analysis our option becomes more close to accept an intelligent source as the causal agent of the origin of complex but meaningful information in the origin of life. In fact, there are strong reasons for acceptance of the presence of intelligence in the origin of life.
First, human experiences confirm that large amounts of specified information in encrypted or coded form in a system invariably originate from an intelligent source. Since a living cell contains huge amounts of information in encrypted form, it appears as a perfect example of the human experience. Secondly, as intellectual identities we can usually detect even the most complicated structure emerging naturalistically and which is not in any way related with any kind of external influence of intelligence. Similarly, we can detect any intelligent design/structure which necessarily involves external intelligence for the design/pattern. Analysis of the structure and functions of a living cell reminds us of the foot-print of intelligence as the causal agent. Because, experience teaches us, that complex systems with specified information invariably arise from intelligent cause. Logically also, one can infer a cause from its effects. Thus, complex and specified arrangement of nucleotides in DNA (effect) implies the past action of an intelligence (cause).
Now, we should revisit function of a living cell to enquire how the question of intelligence comes as causal agent. We know proteins cannot be formed without DNA, but neither can DNA be formed without the help of some catalytic proteins or enzymes. This puzzle - an evolutionary mystery - demands a perfectly coordinated action strategy for survival of a cell and necessarily requires intelligence.
Again, except in a living cell it is nowhere found in nature that one information system gradually evolving into another functional program. For a cell to function, instructions are changed repeatedly for precise functional necessity without any external influence/interference. This pattern of uncertain but highly efficient information flow is available only in a living cell and invariably involves an intelligent agent. Moreover, it is proved that DNA functions like a software program. So, we cannot avoid the question of an intelligent programmer in the origin of life.
It is true that nobody can certainly prove (or disprove) existence of intelligence in the origin of life. But lack of 'hard proof' does not amount to fishing in troubled water too. Among the competing explanations, the possibility of intelligence- based origin of life concept seems correct. Because intelligent agents have unique causal powers that inanimate matters do not. So, the inference of intelligence in the origin of biological information in the origin of life does not depend on any slyness or ignorance but on present knowledge of established cause-effect relationship.