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What is Life?

Animal_diversity

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What is life?

 We can describe the characteristics and infinitely varied forms of living things, but what exactly is life itself? In the past, it was assumed that there was a vital force present in all living things that passed down from life to life. This philosophy was called vitalism. Because it borders on the Devine, today vitalism has been replaced by the philosophy of mechanism, which states that all natural phenomena, particularly life, can ultimately be explained through physics and chemistry. The universe is thought to be merely mechanical in nature. Under this philosophy, life is just a process produced by physical laws acting on matter.

Life is assumed to be a given, like gravity, which incidentally has not been explained or understood well either. We know gravity exists and how it behaves, but really don’t understand why. There is not a single location in any creature or cell that we can point to and say, this is its life. Definitions of Life usually describe what living things consist of and what they do. They do not actually tell us what Life itself is. We can’t collect, isolate or test it, so it appears to be a transcendent quality. What exactly distinguishes a living cell from a dead one or a mixture of cellular components? Depending on the source, explanations vary from biochemical to functional.

Life only comes from life. Spontaneous generation of living things has been shown over and over to be false. Spoiled food does not beget flies or mold. Each only comes from other flies or mold spores. Life as a process requires just the right kind and amount of regulated energy and a fine balance of the right molecules and structures. Science has not been able to create life or even most biological molecules without the help of molecules first derived from living systems or those systems themselves, e.g. bacteria engineered to produce insulin. Even if all of the components of a living organism are blended in the lab in the correct proportions no life results.

What is it that assembles and winds up the machine or provides the vital spark? Science does not know.   Proponents of molecular Evolution believe that non-living molecules at least once in earth’s history spontaneously became a living system from which all subsequent life descended. They argue (and with some merit) that spontaneous generation cannot occur today because living organisms would consume any components before they would have time to accumulate and self-organize into a living system. They assume that only in the absence of life could components accumulate sufficiently to form life spontaneously from non-living components.

Never mind that the key molecules, e.g. proteins and nucleic acids, are unstable in water for the length of time that would be necessary to accumulate and assemble the correct mixture into a living system. These molecules are assembled by linking smaller molecules together with the loss of a water molecule for each link. When excess water is introduced, e.g. ocean or pond, the reactions tend to be reversed and the links fall apart. That is why proteins inside cells are constantly being assembled to replace those that have been degraded. Molecular Evolution proponents believe that production of life in the laboratory can be accomplished at some future time, although they have no evidence to support that belief. We will look at some of the more popular origin of life theories and the validity of the arguments later.

Life is a continuous process that is constantly working against forces that would end it. It has been said that Life (1) is improbable, (2) defies entropy (the 2nd Law of Thermodynamics), (3) is unstable (4) needs a constant supply of raw materials and energy to survive. Let’s look at each of these claims.

 

  1. Life is Improbable

Life really is improbable, partly because of the extremely low probabilities of such complex systems forming by random chance even once. It is the ultimate “Infinite Improbability Drive”[1].   Even the simplest known bacterium contains thousands of types of proteins and other unique biological molecules and structures. Metabolic processes necessary for life depend on thousands of different, specific enzymes for facilitation and regulation through feedback, etc. Enzymes are proteins made of chains of amino acids that are folded into useful shapes. If we suppose that an average enzyme is 200 amino acids long[2], using the 20 left-handed amino acids living beings use, the probability of only one specific enzyme sequence forming at random is 1 in 20200 or 1 in 10260. That’s a 1 with 260 zeros after it.

If the universe is 13.7 billion years old, there have been 4.32 x 1017 seconds since it began. We would need to make 231.4 x 10180 attempts each second since the beginning of the universe to make the random assembly of even this one specific protein plausible – that is, to make the number of attempts that are in the same ball park as the odds against it. This all pre-supposes that all of the amino acids have been pre-assembled and are readily available. Amino acids occur in left and right-handed forms, and only left-handed forms are used by living things. If we take this into account, the odds would be much higher. But remember, to form even one cell all this must happen in a very confined space so that all of the proteins and other molecules can be collected in one place, not just anywhere in the universe or even anywhere on the earth.

If we assume that life molecules were assembled on earth, which is thought to be only 4.5 billion years old, and evidence of life was present 3.8 billion years ago, then the number of attempts per second rises to even more impossible levels by a factor of about 3.4 (13.7/4 billion). And that is just for one protein enzyme assembled from readily available units, excluding interfering molecules, and under the ideal conditions for assembly and preservation. Already we are seeing the extreme odds against a specific enzyme being produced. If we look at what it would take to produce by chance the thousands of different specific enzymes necessary for metabolism, the probability of random assembly of the correct mix would be (20200)3000 for a simple bacterium with 3000 enzymes, or 1 in 10780,000; that’s a 1 with 780,000 zeros after it. The terms “impossible” and “miracle” come to mind.

Now let us look at DNA. There are four different molecules that form base pairs like the rungs on a ladder along the coiled “double helix” of DNA that encodes for proteins, etc. Bacterial DNA, whose chain forms a circle and is tightly wound around proteins, is 300,000 to 4 million base pairs in length. If we assume that a simple bacterium has DNA that is 500,000 nucleotides long, using 4 types of “bases” (two purines and two pyrimidines), the probability of forming the correct sequence is 1 in 4500,000 or 1 in 10301,030 – that’s a 1 with 301,030 zeros after it. Even this presumes that each nucleotide has already been pre-formed from one of the four readily available bases, its partner and a pair of specific phosphorylated sugar (deoxyribose) molecules that form the sides of the “ladder.”

It’s even worse than that, however, since each purine must pair with its specific pyrimidine to form each base pair[3] so double the number is needed. Now add the probabilities of assembling, in one place, the DNA and its associated proteins (histones), the thousands of enzymes and other structures like cell membranes, and it is obvious that the probability of forming even the simplest bacterium is so infinitesimally small that it can only be called either impossible or a miracle. Even if we assume that an earlier form contained a tenth or a hundredth of this number of components, it would still be called impossible or a miracle. For 1% of the components, it would be 1 in (10260)30 or 1 in 107800 (1 with 7800 zeros) for enzymes and 1 in 103010 (1 with 3010 zeros) for DNA (or RNA), plus assembly of all the other components as noted above. Over a ten thousand-fold reduction (0.001%), would be required to make it meaningful, which would leave precious few components to “live.”

One of the origin of life theories proposes that RNA, not DNA was the original control and inheritance molecule. The difference in the structures of DNA and RNA is that DNA uses the deoxy- form of ribose sugar and RNA uses ribose itself. Since DNA now transcribes instructions for protein assembly to RNA first, this theory skips this extra complexity as a more believable scenario. Presently, some viruses use RNA instead of DNA, but viruses are incapable of most life processes on their own and must take over the DNA of host cells to reproduce, etc.   They can be thought of as parasitic “seeds”, not complete organisms.

Fred Hoyle, a famous astronomer and atheist, stated that the odds of forming a living being at random from lifeless molecules would be like the chance that “a tornado sweeping through a junk-yard might assemble a Boeing 747 from the materials therein.” Note that Fred Hoyle and N. C. Wickramasinghe estimated the odds at 1 in 1040,000 by assuming that numerous structures of enzymes could perform the same functions. That’s still pretty steep odds. Others have calculated the odds with various assumptions and outcomes, but all result in extremely small odds. Many are enthusiastic about the possibility of life or life’s building blocks arriving from outer space after being assembled by high energy processes in space. Looking at the extreme odds, pre-assembly elsewhere is like weighing a flea on the back of an elephant. It is not a real answer. Some even have speculated that a more advanced, intelligent life form seeded earth with life, but that only pushes the causes further back in time. How did life come to these advanced civilizations?

All of the extreme improbabilities above don’t even address whether life would spontaneously arise under the right conditions, if all components are available, or whether we would just have the same non-living jumble of molecules we could assemble in a laboratory. In other words, we still haven’t addressed what assembles and winds up the mechanism to start life processes. Clearly, some other unknown process or overarching principle besides random chance has been at work in both assembling the components and in turning them into something alive.

 

  1. Life Defies Entropy (the 2nd Law of Thermodynamics)

Entropy is a measure of the disorder of a closed system and the Second Law of Thermodynamics states that entropy always increases – that chaos always increases and usable energy always decreases. Life seems to defy entropy because life is very, very organized and uses matter to generate energy and build more and more complex structures. However, living things are never closed systems; they need material and/or energy from outside to survive, so an organism that seems to decrease entropy within itself may increase entropy of its surroundings continually. Is it enough to result in a net increase in entropy of the earth or the universe? The answer is unknown but possible. Note that this assumes that the Second Law of Thermodynamics is absolutely true in all cases, but this has not been proven either. It is a well-accepted and thoroughly tested theory and thus is a scientific law by that definition.

A planet with abundant life is far more complex and organized than a dead planet simply because the chemistry of life is far more complex and dynamic than inorganic crystalline structures. It is difficult to see how the net decrease in entropy caused by life on an isolated planet can affect any other planet, much less the universe as a whole. If the planet is considered the “closed system” then there is indeed a net decrease in entropy and a net increase in complexity, order and usable energy, e.g. fossil fuels. Of course, that also depends on your definition of order and disorder. If we define disorder as an increase in the number of states, and order as uniformity of form and function, than the dead planet is not as disordered as a planet with abundant life in all its forms and complexity of functions. However, if disorder is the rule, then the ultimate outcome of continued disordering and loss of energy is a uniform, cold, dead universe in the lowest energy and organizational state possible.

 

  1. Life is Unstable

Life is indeed unstable because it exists on the edge of destruction, far from equilibrium. Ordinarily, chemical reactions reach a state of lowest energy called equilibrium where they are stable. At that point the reaction stops or is stabilized dynamically where the net amount of products no longer increases and the net amount of starting materials no longer decreases. Life is never at or near equilibrium and requires input of material and energy to maintain itself in this unstable state. It can only exist under very specific physical circumstances including temperature, pH, pressure and presence or absence of oxygen. An aerobic organism requires oxygen, whereas oxygen is deadly to an anaerobic organism. The only time an organism is stable or at equilibrium is when it is dead. This brings us to (4.).

 

  1. Life needs a constant supply of raw materials and energy to survive

Life requires a constant or nearly constant supply of materials and energy from outside itself to survive. Ultimately, most of life on earth depends on the products of photosynthesis as a source of energy that is initially derived from the sun. The only exceptions are those living systems present in deep seas and deep interiors that derive energy from bacterial processing of inorganic chemicals such as hydrogen sulfide. In both cases, energy and material from outside the organism are necessary to maintain life.

Since no one knows what life actually is, the best we can do is define what living things must have and must do to live. All living things are more alike than different. An advertising flyer I received a few years ago from a supplier of products for biochemistry stated “Did you know that humans share about 50% of their DNA with bananas?[4]” All living things use essentially the same basic biochemical processes such as metabolism in the everyday business of living, so the DNA that encodes for the chemicals used for life processes are necessarily very similar. The differences are relatively minor compared to the similarities. The processes used to accomplish all of life’s functions at the molecular or cellular level have to be very similar for all living beings. Because the processes are so complex and similar, the surprising thing is not that the workhorse protein molecules (and thus the DNA that encodes for them) of different living things are so similar, but that they are as different as they are and still function in essentially the same way.

Living things at the minimum consume and process food, excrete waste, grow and reproduce. Some evolutionists would add “and, through natural selection, adapt in succeeding generations”[5]. Some living things also move, sense and communicate. Some can even go dormant for long periods and only “come to life” when conditions are right. This is true of many bacteria. Bacteria that had lain dormant for 120,000 years have been found under Greenland’s glaciers[6]. Once, I left a closed jar of saturated salt solution, which I had used to treat a sore throat, sitting for a month or so. When I started to throw it out, there was a fuzzy white ball of bacteria floating in the middle of it. This extremophile[7] bacteria that could grow in this high salinity environment was probably from the salt and may have been dormant for thousands of years before awakening[8]. Re-vitalization of dormant organisms is a great mystery. How can life itself be suspended and then be restarted spontaneously?   Is it really suspended or is it just slowed to an imperceptible level? But how could it survive for thousands of years?

So, we are only left with questions about what life is and how it came to be. Obviously the odds against life forming spontaneously put it into the realm of miracles, unless there is some as yet undefined and undiscovered process or principle. In a later post, we will examine some of the theories put forth to try to explain life’s origin.

[1] Hitchhikers Guide to the Galaxy, Douglass Adams, 1979. A satire in which instantaneous intergalactic travel is possible due to an infinite improbability drive.

[2] Note that the hypothetical numbers given here of amino acids, proteins and DNA nucleosides in a simple bacterium are simplified to make calculations easier.

[3] Purines Adenine (A) and Guanine (G) must pair with Pyrimidines Cytosine (C) and Thymine (T), only as A-T and G-C to form each nucleotide pair that forms each “rung” of DNA. RNA substitutes Uricil for Thymine.

[4] Sigma Life Science, part of Sigma Aldrich Company, St. Louis, MO, USA. http://www.sigmaaldrich.com

[5] Life, from Wikipedia

[6] Tiny Frozen Microbe May Hold Clues To Extraterrestrial Life, Science Daily (June 15, 2009) — “A novel bacterium — trapped more than three kilometres under glacial ice in Greenland for over 120,000 years… Dr Jennifer Loveland-Curtze and a team of scientists from Pennsylvania State University report finding the novel microbe, which they have called Herminiimonas glaciei, in the current issue of the International Journal of Systematic and Evolutionary Microbiology. The team showed great patience in coaxing the dormant microbe back to life; first incubating their samples at 2˚C for seven months and then at 5˚C for a further four and a half months, after which colonies of very small purple-brown bacteria were seen. … and it has been shown that ultramicrobacteria are dominant in many soil and marine environments.”

[7] Extremophile – bacteria that thrive in extreme conditions that would kill other organisms. They have been found in boiling hot water, under extreme pressure, at high altitudes, in sulfuric acid rich waters, in oil wells, etc. Almost no place on earth is devoid of life. It is ubiquitous.

[8] Table salt is produced in two ways, mines or evaporation of salt water, so it is uncertain if this was an ancient organism. Ponds used to evaporate sea water are often tinged purple or red by halobacteria and must be purified before sale for food products, so salt with dormant microbes was probably mined from deep underground.

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