It is estimated that our earth was bombarded with life destructing cosmic radiation 700 million years after its creation. We do not know exactly how carbon-centered life came into existence and we can only make assumptions based on clues. As the verse goes, we did not witness the first creation of life (Qur’an 18:51, 43:19). However we can develop various scenarios through traces left by the earlier events. We know that the first traces of life on earth date back to around 4 billion years ago. The molecular basis of material life relies on the facts of quantum world because chemical affinities of biochemical molecules, conservation of catalytic domains/surfaces and formation of three dimensional structures all depend on principles of quantum mechanics. Microscopic pores of clay crystals or oceanic basalt (a type of volcanic rock) are suitable for synthesis of complex organic molecules.
If planet earth did not have plate tectonics, problems would occur with the logistic flow of materials needed to be used for the formation of life. For instance, if carbon stored in carbonated sediments meets water, it dissolves as CO2, and then released into the atmosphere. These tectonic movements constantly generate new materials ready to be oxidized, thus preventing oxygen ratio to reach dangerous levels. The reason Mars has been a dead planet is because all its tectonic movements almost have come to a halt. Plates gain high level of flexibility with the water content of the earth crust. This way, both the gliding of tectonic plates over one another and the continuous flow of inner planetary material towards the surface is enabled.
One of the scenarios regarding where life on earth had started relies on the hot springs at the bottom of the oceans as being the earliest and most suitable places for life. These environments located near the inner crust of the earth are host to micro-organisms since those times. Therefore, the first organisms on earth are most likely to be organisms (hyperthermophiles) living in high temperature waters.
Furthermore, because ribosomes are the protein makers of the cell, when ribosomal RNA’s sequence analyses were compared, it was understood that hyperthermophilic organisms were among the first life forms. Stability of DNA and proteins are at risk when they are over 100 °C, so that is the reason today’s hyperthermophilic organisms are equipped with enzymes that recognize and repair high temperature damage and respond to specific thermal shocks.
This finding constitutes evidence that the earliest signs of life appeared on the critical boundaries of high temperature conditions and thermal degradation. Thus, there is a great possibility for chemotropic microorganisms (methane bacteria) to be considered among the earliest creatures as they utilize inorganic substances in order to generate energy to maintain their lives. Methane bacteria have been supplied with conditions for their survival which is characterized with their ability to produce methane from dissolved hydrogen and CO2 in the water. The fine balance here can be observed in the critical properties of water. If water a) was not separated into hydrogen and oxygen while it passed through hot rock layers, and b) was not returned back to the surface after the tectonic circulation via leakage through micro holes of rocks, and c) did not have the capacity to dissolve both hydrogen and CO2 in sufficient levels, chemotrophic organisms would not be able to have a sustainable life. This is because the supply of required raw materials for energy production is linked to physicochemical properties of water as part of the causation chain. Another important property of water is that it can be transported in carbon nanotubes as this property has critical importance, especially in relation to plant osmosis and cell membrane transport of protons. In the formation of these properties of water (such as the dedication of electron and proton mass value and charges), the phenomena of fine balance during the earlier moments of the universe has a significant role.
How dependant is life on water?
There is no evidence up until today that shows the presence of an organism which can live and reproduce completely without water. The most dangerous factor for a life on land is the dryness of air in lethal levels (Zero humidity ratios). When the air is at 20 °C and with 50% humidity, cells carry 0.1 gr. of water per dry biomass. Cellular metabolic functions come to a halt when water concentrations drop to this level. This is deadly for many plants and animals. However, an unknown percentage of microorganisms and few plant and animal species are equipped with such mechanisms to be able to withstand drought in an ametabolic state for hours or years. Returning back to their ordinary living functions and activities depends on their coming in contact with a humid environment or water. Drought tolerance is very limited, so is the number of tolerant species and their quantities.
Scientists have been conducting extensive research on these organisms and have found that these organisms are equipped with protective proteins, with sugars that do not lose function in dry environment, and with genes uniquely assigned to regulate the syntheses of these proteins and sugars, and that they are so finely incorporated in these organism’s genetic and metabolic programming – these facts are truly amazing and indicative of an all-comprehensive knowledge and willpower constantly operative in the universe. For instance, Trihalose sugars are utilized during drought tolerance response in animals. This type of sugar indeed increases drought toleration in human thrombocytes to some level. It has been proven that the longevity of dried plants depend on the fat content of their cell membrane and particularly the number of double bonds in acyl chains. Without losing vitality, time for seed drying gets shorter as the number of double bonds increase. Also, if cells cannot renew the reduced form of Glutathione as it functions in the removal of oxidation causing agents during both the drought and drying process, programmed cell death is initiated.
Aphelenchus avenae, one of the nematodes (round worms), can regulate expression of genes encoding proteins pertaining to drought resistance according to the presence of water. Nemotadoes living in Antarctica become active with a slight increase in soil humidity. Extreme humid conditions however cause a shorter life span in these animals. Studies exhibit that drought is not a favorable living condition and that life forms increase productivity as they distance themselves from drought. The factors that contribute to famine outside of anthropologic elements can be listed as dry climates and drought intolerance of the human body. Studies regarding drought resistance gene transfer have been going on via plants and animals which can bear such toleration.
The genes that hold the information in their structures in order to provide drought resistance have gained importance in such environmental conditions and can be noticed more frequently. All of these illustrate that major roles have been assigned to water in terms of formation and maintenance of a carbon-centered life on earth. The difference between organisms which have resistance to drought and those who have resistance to dehydration are hidden in the details at the molecular level.
Fine balance in early life forms
We are witnessing a great deal of diversity on earth because every single event that has happened since the beginning of the universe was made suitable for life. Microorganisms living in deep ocean hot springs, in freezing cold regions of Antarctica, in extremely acidic or saline waters are very good examples for this. If human skin was to touch these kinds of acidic waters, it would cause severe burns. Pyrolobus fumarii, a hyperthermophile organism, lives in volcanic pits as hot as 90 to 121 °C and proliferates at 121 °C. In recent years, archaebacteria species which can live in 130 °C heat have been isolated.
Saline water has the property to stay in a liquid state even in -20 °C. Properties of water like heat conduction, heat preservation, solubility, viscosity, surface tension, and cell membrane interactivity should be reinvestigated for temperatures between -15 °C and 130 °C in which life can be observed. One important feature of water is that it retains its fluidity over dirty surfaces and over thin films that form on ice crystals, even in temperatures below freezing point. Physical and chemical properties of water in ultra-cold micrometer thin films are different when compared to normal conditions. There are many microbial organisms living in life-permitting conditions generated on these thin films. Specific organisms have been created for every climate type and location on planet earth. Microorganisms and plants (psychrophilic) living in extreme cold conditions (between -10 °C and -20 °C) are great examples of this phenomenon.
It may be considered as a law operative in nature that organisms living in the same environment from different categories of life are created equipped with common features adapted to that habitat. Such features, motifs and adaptive processes that are repeated and conserved among living things in fact indicate the One and His creative power in unity. The overlap and correspondence of biological features of livings things with their living conditions is an important evidence for the fine balance phenomenon of organisms. The commonality between the polar cod (Boreogadus saida), which is a significant source of trade in the North Sea, and distant fish species such as Dissotichus mawsoni, which live in the cold waters of Antarctica, lies in the fact that they both have the genetic information for the antifreeze feature. This genetic information involves synthesis of an antifreeze protein with a repeating Threonin, Alanine and Proline amino acid motif when expressed as an antifreeze feature. This specific protein present in the blood of both fish is in charge of inhibiting proliferation of ice crystals which therefore prevents fish from freezing.
Molecules that function with water
If one observes the events that are taking place in our nature and universe with an objective lens, the presence of purpose and target centered processes and behaviors (teleological) in each stage are witnessed. Properties of water, particularly the presence of suitable chemical (hydrogen) bonding strength in transcription, proliferation and expression of genetic programs, show the fine balance phenomenon. If the hydrogen bond strength between DNA, RNA strands and of matching nucleotide bases were different, both translation and amplification of these messages coded via DNA and RNA would be impossible. Another striking aspect of the fine balance phenomenon is seen with Serine proteases in charge of protein degradation.
The reason that these enzymes are known as subtilisin in bacteria and trypsin in vertebrates is because of the presence of different amino acid sequences and three dimensional structures in each of these proteins. However, there are three common amino acids that are conserved in the active site of both of these proteins, as if generated by a single hand. These amino acids have vital importance to the function of trypsin and subtilisin, and they only differ in their positions throughout the protein. In Trypsin Histidine, Aspartic acid and Serine is respectively located as the 57th, 32nd and 195th amino acid, but in subtilisin the same aminoacids are respectively located in the 64th, 32nd and 221st positions.
Can the functional choice in the location of these amino acids be considered as coincidental or self-occurring? It is very difficult to convince one’s mind and heart to answer this question in the affirmative.
Hamza Aydin is a professor of biology and freelance writer based in Turkey.