life

   Don't Ask A Physicist

In today's post, I'm writing about something that I actually know about, and that is biology. I am not saying I'm an expert on all the varied topics that make up this most wonderous of subjects. That would just be silly. But at least I have spent a reasonable amount of time in a formal educational setting studying many of the diverse areas that constitute the condition that is 'Life and all that Entails/Entrails'. And at least in one arena of the subject, Human Genetics, I could be considered an expert- whatever that means. Although, I do confess I'm a tad rusty on the rapidly developing technology these days. The point of this diffuse ramble? In this post, at least, I don't have to pepper my introduction with caveats and limitations as is my wont when dealing with topics outside my sphere of expertise. I'm not saying that this post is error-free. But I am saying that my errors are at the very least, informed errors. With the caveat, so stated, allow me to write anew/askew.         

Life, the great mystery:- I've approached this ultimate puzzle, previously, on this very blog, and from several directions. And indeed, there is much to ponder. In today's post, I'm taking a fresh and wry look at the ultimate question.  

Let us look back to when the primordial Earth came into existence 4.6 billion years ago. At birth, and for at least a billion years into its infancy, our planet was a mass of seething, roiling molten rock. During this time the primal Earth was subject to numerous asteroid impacts making the surface extremely bestrewn and chaotic. The energy imparted by these impacts helped to maintain the molten state. It was during this tumultuous era, that a Mars-sized mass slammed into the Earth sending a lump of molten debris into space. Once cooled that 'debris' would form our only Moon. Eventually, the great bombardment would cease and the Earth's surface would cool sufficiently to a point where life could form without the hindrance of 'Thermal Insult'. This occurred about 3.8 billion years ago.

In the scorching interior of Australia, there can be found mounds of fossil bacteria laid down 3.5 billion years ago. This represents the earliest evidence for the presence of living organisms. Thus, we can state that life was certainly present just 300 million years after our world had become 'quiescent'. Now, this might seem like a long time interval but in terms of geological history, this is but a blink of a ferret's eye. And, when we examine the fossil evidence relating to this early organism it is obvious we are already dealing with a well-evolved bacterium suggesting that life on Earth had formed many million years previously. 

So, how did the first life come about? The quest to uncover how life formed from non-life is a post for another day. Hopefully, I will be able to publish, on this very organ, within the next few days, about the thorny problem of Abiogenesis.

But before I begin to tackle this most vexing, and most fundamental of inquiries I would like to jump forward, a step, and address and be propelled to consider the following question, namely, how do we define life? What are the characteristics of life that distinguish it from non-living stuff? This is a deceptively difficult question and it will be useful to contemplate the problems that arise when we try to grasp this particularly slippery ferret by the tail (Flaxen, steady with the incipient waxing, especially ferret waxing). From first principles and intuition, it is relatively easy to list the properties that life, may, or must have, to 'exist'. Students during middle school biology classes are usually taught the acronym MRSGREN, which represents: Motion, Respiration, Sensitivity, Growth, Reproduction, Excretion and Nutrition. Even from a cursory glance, it is clear that not all living things are so well-endowed. Of all these characteristics, a few stand out as universal. Thus, ALL living organisms, irrespective of phyla, must have a means of propagation, regardless of whether it is asexual or sexual, or both. Also, a means of collecting energy, or manufacturing energy, is a universal feature amongst the living. The other characteristics, so stated, are negotiable and dependent upon the biological complexity of the creature in question. For instance, mammals appear to be endowed with the entire collection of life's dynamic qualities. At the other end of the spectrum, viruses, appear to be equipped with nowt, apart from reproduction. And yes, I'm well aware that not all biologists think that viruses constitute life. I'm not going to squeeze into this particular lagomorphic hole today. And anyway, I've already written (x2) about this subject- go seek and be amazed!

Is life special?- this might appear to be a stupid question, but the answer is elusive on mature reflection. Erwin Schrodinger, he of quantum dynamics fame, reduced life to its ultimate base state and described 'life' in terms of the Second Law of Thermodynamics. Simply stated, this law describes the flow of energy in enclosed systems. Inevitably, the flow of energy in any enclosed system has a spontaneous tendency toward disorder (entropy). Thus, Schrodinger explained life as an enclosed system that harnesses energy to reverse the process of entropy. However, the laws of the universe are not to be trifled with, or denied, and once the organism expires, the inexorable process that is entropy proceeds unhindered. Therefore, this decisive and reductionist definition of Life can be explained tersely and as follows: A transitory suspension of the Second Law of Thermodynamics within a closed system. Do you find this definition a valid description of 'Life'? Well, this definition is not an exclusive property of life. There are myriad examples of inanimate objects disobeying the entropic principle, albeit for a little while. Consider the car in your garage, for example. What about a guttering candle? And so the list goes on.  

There are those, often embued with a mystical quality, who think that there is an ethereal spark that induces the inanimate to become animate. This mystical force is synonymous with the concept of the 'soul' (perhaps). A force field that is present but departs upon death to go elsewhere. Religions, various, are rather keen on the idea and have been so for millennia. Christians are supposed to take heed of the eternal soul. It used to be thought that the soul was the sole property of Homo Sapiens and that lesser breeds had to make do without. And yet modern genetics has shown that hubristic humans are not that much different from many of the supposed 'lower species'. Even the humble mollusc, especially those of the class, Cephlopodia, have shown traits that we consider intelligent. The 'Soul Concept' is essentially a philosophical question outside the domain of scientific study. Although, I will say, there is absolutely no scientific empirical data to support this notion. Take it as you will.  As said, my next post will consider the question of how life first came about. This is enough for today.