As I mentioned earlier, awareness is similar to other features of living things (such as legs, arms, leaves, wings, roots or teeth) in that it evolves in stages over time, becoming more complex with the passing generations.
As I also mentioned earlier, different life-forms exhibit differ-ent degrees of the quality - such as the sunflower with its basic awareness of the position of Sun and the chimpanzee with its more sophisticated awareness of the usefulness of sticks. And then of course there's us, with our ridiculously highly developed sense of awareness.
All forms of life sit at their own specific points along a scale of awareness levels, starting at zero awareness (for a blob of inert chemicals), passing upwards through intermediate levels for protozoa, sunflowers, houseflies, birds, chimpanzees and so on, and ending, for our purposes here, with us (The spectrum of awareness levels may well extend into invisible zones that are beyond our comprehension, analogous to the way that the visible spectrum does, but by definition we can't actually be aware of those zones).
To study this spectrum of degrees of awareness, let's start by considering how the very lowest level of awareness may have come into existence to begin with - the foundation on which the whole edifice of awareness is built.
Let's go back three or four billion years, to a time when life on Earth was just starting to develop.
Exactly how life came into being is shrouded in mystery, as you'd probably expect, but that hasn't stopped people coming up with numerous theories on the matter.
A common thread in the more sensible of the theories is that life started in water. The theories often go like this.
In the time immediately before life started there was possibly a bringing together of complex chemicals (such as amino acids) in certain localised bodies of water, forming concentrations of these chemicals in relatively small areas. This was the natural consequence of normal physical processes - for instance seawater may have gathered in shallow coastal regions and evaporated, creating abnormally high concentrations of chemicals in the water that remained in small rock pools. These concentrations of complex chemicals were then in a propitious position for being acted upon and altered (and thus made more complex still) by a source of energy such as sunlight, or possibly lightning..
It's possible that as a result of their chemical makeup these concentrations of complex chemicals may have formed into small roundish masses or globules. It's then quite possible that the outer surfaces of these globules became more solid than their interiors (due to some normal chemical processes, analogous to the way that a crust forms on cooling lava or the film of ice forms on freezing water). As a result the globules would have formed membrane-like shells, holding the contents of the globule in a secure package. These globules were the precursors to the living cell.
Over time, and aided by the heat in the water around them, the trapped chemicals within the membranes of these cell-like globules would have reacted with each other to produce the antecedents of the proteins and nucleic acids that are found in modern cells. They would also have begun to interact in a way that caused the individual globules to split into two (or more) separate globules.
The fact that these globules could split into more globules meant, in other words, that they were self-replicating. This ability to self-replicate is one of the most fundamental and important features of living things. The globules fulfilled the most basic criterion of being alive. They had become primitive living cells.
The chemical composition within the cells was intimately locked onto the structure of the longest nucleic acid molecule within the cell. In these early cells this molecule was probably RNA (ribonucleic acid), which is related to the DNA (deoxyribonucleic acid) that is found in all living cells today.
Whenever one of these cells split into separate cells each new cell was almost identical - but not quite. The imperfection of the split meant that the nucleic acid in each cell, and thus the whole chemical makeup of each cell, was very slightly different.
This difference between the cells - this imperfection - meant that different cells would react ever so slightly differently to their surroundings, as I'll illustrate in a moment. This, in turn, meant that the cells could, through successive splitting, develop more complexity, resulting in more complex life-forms.
You may have noticed that in the description that I've just given, the origins of life are brought about by nothing more than an amalgamation of appropriate chemicals and a heat source such as the Sun. There was no special "spark" or "life force" that was somehow brought into being at one significant instant, or that was mysteriously injected into the chemicals involved. The only thing that happened was that clusters of complex chemicals split and formed other, slightly different and more complex clusters of chemicals. Quite boring really.
A crucial element in the development of these simple cells on their extremely long haul to become complex life-forms was the emergence of the capability to react to the environment that was around them. Let's see how that may have come about.
(The exact scenario painted here is necessarily speculative, as no-one knows much about the conditions of early life on Earth. However, that isn't a great handicap, as the description here should be treated simply as a model, used mainly to illustrate the general dynamics and interrelationships of the processes that may have occurred. They can easily be transferred to a different setting or stage.) Imagine a pool of water containing some of the single-celled living organisms just described - the earliest and most primitive of life-forms - life-forms that are indeed only just on the right side of the definition of what it is to be alive. These cells are all the result of the splitting, over time, of a single common ancestor. As a result they are all very similar to each other apart from the minor inevitable variations that are the result of the inherent inaccuracies of the splitting process.
For the single-celled organisms to be able to survive in the pool, the water in which they float needs to be warm. This is because the living cells need energy that they can absorb in order to split or replicate. However the water mustn't be too warm or the chemicals within the cells will become too jumbled up to react in this way. For similar reasons, the water mustn't be too cool either. The water must therefore be within a very particular temperature range.
Here in Figure 57 are the single-celled organisms in the pool of water (I've made the organisms look quite large purely so that they can be seen easily in the illustration).
Imagine that the water in the pool is heated by the Sun. The Sun heats the water at the surface more than the deeper water, so the water gets progressively cooler with depth. This change of temperature is known as a temperature gradient.
Our single-celled organisms have to be at just the right temperature in order to survive - if they are too warm or too cold their chemicals will be adversely affected and they will not be able to maintain their integrity - in other words, they will die.
Between the top of the pond, which is too hot, and the bottom of the pond, which is too cold, is a layer of water that's at just the right temperature for the organisms to survive. You can see all of the cells floating in the layer (which I've shaded gray).
It's tempting to imagine that the cells sensed that the water in this layer was at just the correct temperature for their survival and that they therefore chose to float in that particular layer.
However, that's not the case.
These are very primitive single-celled organisms remember, and they have absolutely no senses whatsoever with which to notice the world around them. As a result they wouldn't have the ability to detect the temperature of the water.
The organisms do not know - in any possible sense of the word "know" - what the water's temperature is. Indeed they do not know that they are floating in water to begin with. They do not know anything.
So how did they come to be suspended in the water that's at just the right temperature? Before we answer that specific question we need to know why they are suspended in the water at all, rather than floating on the surface or sinking to the bottom, which is what most things do.
The cells are suspended in the water because they happen to have the correct degree of buoyancy to make them do so.
What exactly is buoyancy? Archimedes, mentioned earlier, gave us the answer. When an object is placed in water it tends to float or sink. If the density of the object is less than that of water it floats (An object that's less dense than water is one that weighs less than an equal volume of water - so for instance, if a two inch cube of a material weighs less than a two inch cube of water the material will float). If the object's density is greater than that of water it sinks.
If an object is exactly the same density as that of water it will neither float nor sink, but will remain suspended in the water at whatever depth it happen to be at. This state of equilibrium is known as neutral buoyancy. (Humans are almost at neutral buoyancy in water, especially salt water, which is why we hover between floating and sinking when we're swimming.) The cells in our pool are at neutral buoyancy, so as a result they are suspended, neither rising up to the surface nor sinking down to the bottom. How come they just happen to be of a density that affords them neutral buoyancy? Pure chance? Not really.
Due to natural random variations on replication, cells would be created at a variety of densities, and thus with different buoyancies. The less dense cells would float upwards to the surface of the water, while the more dense cells would drift downwards to the bottom. In both cases the cells would find themselves in water that was of the wrong temperature for them to function properly, and they would effectively "die" (I'm using the term die in a very loose sense here, due to the fact that, as I've emphasized, the cells only just scrape through the most basic definition of being alive to begin with. It's probably more accurate to say that they enter a state of inertness).
As a result, only cells that happened to have the correct density to achieve neutral buoyancy would survive.
I mentioned that objects that are the same density as a liquid, and thus are at neutral buoyancy, can remain suspended at whatever level in the liquid they happen to find themselves..
However, the cells in the previous illustration, Figure 57, are all at the same level in the liquid. How can this be? This is because although the neutrally buoyant cells can be suspended at any level within the water those that are at levels that are outside the "just right" layer will be either too warm or too cold for their chemical contents to replicate themselves (Figure 58). As a result the cells in the too warm and too cool zones will not multiply and will probably have their chemicals jiggled around so that they will die (or become inert if you prefer).
The only cells that can replicate are the ones that happen to be in the just right zone.
(The dynamic involved is a little like the one I described earlier involving moths, where only those moths that happened to be the same colour as the tree bark survived. In the moths' case the agent that killed the unsuitably coloured moths was a predator, while with the cells the agent that killed the unsuitably buoyant cells was temperature.)
So it is that the living cells are found in the layer of water that's at the correct temperature - not because the cells chose the layer but because that's where they just happened to be, in the layer in which they wouldn't die.
When the cells in the just right layer replicate some of the resulting cells would be of different densities, due to random variation, and would drift up towards the surface of the water or down to the bottom, thus exiting the just right zone. These cells would find themselves in water of the wrong temperature and would die.
Cells that remained within the just right zone would survive and would replicate further, with the result being that the just right layer of water would find itself teaming with single-celled organisms, while the rest of the water, being either too warm or too cold, would remain barren and devoid of life, although not devoid of non-functional, non-replicating "corpses".
Thus it is that slight variations in the characteristics of an organism (in this case its buoyancy) may mean either functionality or non-functionality - life or death.
The scenario painted here is fine as far as it goes, with its simple pool of water in which the liquid remains within a stable and acceptable temperature range for the cells to survive. But nothing in nature is static, so the pool in my illustration would not remain stable and acceptable for long.
Forces such as convection currents caused by the Sun heating the water would cause disturbances and would move some of the cells that existed in the habitable zone up or down towards the uninhabitable regions. Some of these cells would inevitably enter the hostile regions and would die.
However, some of the cells that drifted towards the hostile zones may not die - due to fortuitous variations in their makeup caused as an inevitable result of the normal, inherently imperfect replication of the cells.
Imagine the following cell for instance - a particular cell that reacted in a specific way to temperature change.
This particular cell had a slightly different composition to the other cells - a composition that made it react to warmth by partly shrinking or shrivelling up (perhaps by expelling some of the water that was inside it).
When this cell was carried upwards towards the region of warm water (perhaps caught in a convection current that swept it in that direction) it would shrink.
Once it had shrunk the cell would be slightly smaller and denser than it had been previously. This would make it less buoyant, which would stop it rising upwards and would make it drop back deeper into the water - taking it back down into the habitable layer.
As the cell cooled slightly on re-entering the cooler habitable zone it would expand slightly and revert to the state that it was in before it was swept upwards. Its original neutral buoyancy would thus be restored and it would once again reach a state of suspended equilibrium in the water, neither floating upwards nor sinking downwards.
If we'd been on the scene to observe this action we'd have observed the cell drifting upwards towards the danger zone, stopping near the edge and returning to the safety of the habitable zone.
This would look very much as though the cell could sense the unwelcome temperature change as it drifted towards the warm water, and that it had chosen to return to the just right zone. But this isn't the case at all. The cell changed direction purely because its size had changed (thus making the cell denser and less buoyant) - and this size change was a simple physical process. The cell was in fact functioning like nothing more than a primitive, organic thermostat.
This property of the cell - of changing size (and thus buoyancy) as the temperature changed - is a definite advantage, making the cell much more likely to survive, and as a result multiply. The cell's offspring would tend to inherit this tendency to change size (and thus buoyancy), subject to the usual minor variations due to the imperfection of replication, and the trait would thus become an integral quality of the new improved, upgraded organism.
It's important to remember that, due to the random variations in offspring that occurs when cells divide, a cell wouldn't necessarily only create offspring that fortuitously shrank as they approached the warm water layer (and thus sank back into the "just right" layer), it may also create offspring that expanded as they approached the warm water, due to their slightly different internal chemical composition. These cells would thus become more buoyant as they floated upwards into the hostile zone and would therefore rise even further into the warm water rather than dropping back to safety. As a result they would perish - making it impossible for them to pass their rather unfortunate characteristic on to future generations.
Such is the way that random characteristics can turn out to be a help or a hindrance, with only the helpful ones surviving to replicate another day. (Again, this is a dynamic that was described earlier, in relation to the thickness of fur on a fox and the colour of a moth: some foxes were unluckily born with thin fur that made them more susceptible to the cold, and some moths were born with lighter colours that made them stand out more on the tree bark.) Over time, successive generations of the simple single-celled organisms would acquire further characteristics due to the random variations that occurred on replication.
These characteristics would make the cells react to their environments in ever more complex ways. I'll just quickly describe a few of these now. (If you read that sentence and thought "That sounds a bit tedious," fight that feeling, because this is important. It's all about the creation of the blueprints for how we, at our position at the opposite end of the evolutionary scale, still act.) One of the ways in which the cells may have reacted to their environments in ever more complex ways may have been that they became so sensitive to variations in the temperature of the water around them that they reacted by different amounts when one side of the cell was at a slightly different temperature to the other side (Figure 59).
The reaction involved could be that the cells changed shape in some way, more on one side than the other (such as by expanding on the warmer side), or maybe the reaction could be that the cells ejected water or chemicals through their surface as they warmed up, with more being ejected from the warmer side than the cooler.
The difference in the extent of the reaction on either side of the cell may have the interesting side effect of making the cell move within the water. This is easiest to imagine in the scenario in which one side of the cell ejects more water or chemicals than the other side. Imagine a cell warming up, and as a consequence water inside it starting to seep through the outer membrane of the cell. More water will seep through the side of the cell that is warmest, and as a result a sort of low grade "jet propulsion" would make the cell drift in the direction opposite to that of the ejected water.
This could have interesting consequences.
It may mean that when a cell was in a region of water at the boundary of its safety zone, where the water was getting too hot on one side, the cell may react to the variation in temperature by moving back into its safety zone.
In this way the organism moves in an advantageous direction. It will have gained the power of what you may call self-propelled movement. But again, as with the movements illustrated previously due to buoyancy changes (in which the cell drifted up or down in the water as its density changed), this motion is instigated purely as a physical reaction to an outside stimulus - the cell is not sensing the temperature of the water around it and then making a choice about moving.
This is made evident, if evidence were needed, by the fact that other cells may just as easily develop a similar method of propulsion but in the opposite direction - the direction that's towards the water that's the wrong temperature rather than away from it. As a result, they would perish.
The actual method by which the cell attains movement is not important in itself, the only thing that matters is that it does so. My example of a jet-propelled cell is perhaps rather fanciful, however for the sake of illustration it's somewhat easier to follow than examples involving convoluted changes of cell shape that allow the cells to "ooze" through the water.
Self-propelled movement is definitely an advantage, provided it's in the correct direction, so organisms with this trait would prosper. Self-propelled movement in the wrong direction would mean certain death, so this trait would lead nowhere.
The cells described in the scenarios above definitely react to their environment. This, in the loosest sense of the word, makes them in some way "aware". Their reaction is, however, at the very bottom of the scale of awareness: at the level of automatic reaction at a chemical or mechanical level to outside forces. At this level, although the cells react to their surroundings it can't be said in any meaningful way that they actually sense their surroundings.
Notice that in all of the examples that I gave above the organisms involved survive by being capable of staying exclusively within the "just right" temperature zone. They have to be inside this zone to start with (as otherwise they'd be dead), and to stay within the zone they need to be capable of moving away from environments that are not conducive to their survival should they start drifting in those directions. They don't survive by having to move towards the just right environment (as they are in it already). They in fact exhibit repulsion from the danger zones that surround them, which has the happy effect of keeping them safely corralled inside their habitable zone. They specifically don't exhibit attraction towards the habitable zone.
Maybe you're thinking "If this organism is exhibiting repulsion from the hostile zone, isn't that the same as exhibiting attraction to the habitable zone? It's simply a different perspective - a different way of looking at it." Not quite. This is because the phenomena of repulsion and attraction have separate, independent existences. Although they are opposites in meaning they aren't opposites in the sense of being an inseparable pair that must exist together at all times (as is the case with such yoked pairs as top and bottom).
So it was that in this early world of single-celled organisms only repulsion existed. Attraction was nowhere on the horizon. This is important, and will be a recurring theme in this story.
Repulsion sounds as though it has the quality of awareness shackled to it somewhere (as in when I exhibit repulsion whenever I tread on a slug), but again, in the case of these single-celled organisms the awareness that's exhibited is at the most basic level. The sort of repulsion involved here is very much of the mechanical type - analogous to way that the same poles of two magnets repel each other or the way that water and oil repel each other if you mix them. The only difference is that in the case of the cells it's being applied to things that have the ability to replicate, and that are thus, at the most basic of levels, alive.
In my description so far the only reactions that have taken place for our single-celled organisms are repulsions - because the organisms involved only needed to avoid entering hostile zones (as they inhabited the just right zone already).
This limited degree of reaction was fine as far as it went, keeping the organisms safely contained in their environmental niche. As long as the environment remained reasonably stable the organisms could exist indefinitely.
But of course things change.
It's at this point that the quality of attraction may have come on the scene, to join its relative (though not its yoked opposite), repulsion.
Here's a description of the sort of route by which this may have happened. (Once again, the scene painted below is not meant to be a description of what actually happened. It is a deliberately oversimplified scenario that is advanced purely to describe the sort of underlying dynamic that may have been in operation - the actual engine that was driving that dynamic could quite possibly have been something totally different, and would inevitably have been more complicated.) Let's return to the layer of just right water that we've been contemplating so far.
Time has passed and the layer would be teaming with life, because the cells in it were thriving in the perfect conditions. The organisms may be moving around a little, using the power of movement that they'd developed, as described previously, that allows them to automatically stay in their comfort zone should they drift towards the edges. The movement of the organisms would result in the water being agitated slightly, sending vibrations out through it.
These vibrations in the water would physically affect the organisms: the vibrations after all are just molecules of water moving, so these molecules of moving water would be hitting the organisms' outer membranes and making these membranes vibrate a little themselves.
You can see in Figure 60 that any organisms that were on the outer edge of the mass of organisms and that were thus closer to the hostile zone would experience fewer vibrations coming from the side that was towards the hostile zone than the other sides, because there would be fewer (or no) organisms in that direction agitating the water, due to the fact that the hostile zone is devoid of organisms (other than dead ones).
This unequal amount of vibration near the edge of the habitable zone may make an organism that happened to be at that boundary react in a specific way (such as by changing shape) that would make it move in the direction of the mass of the vibrations and thus make it move further into the habitable zone. The reaction to this vibration gradient could be very similar to the reaction to the temperature gradient described earlier (Figure 59).
The result of this useful reaction would be that the organism would have by chance acquired another regulatory system that kept it safely in the comfort zone along with its fellow organisms. Remember that the organism is totally unaware of the existence of its fellow organisms, as it's completely devoid of senses and is simply reacting directly and mechanically to the vibrations that are hitting it - but the result is that it moves towards the mass of other organisms.
(Again, some organisms may react to the unequal vibrations on their membranes by moving away from the direction of the source of the vibrations - but these organisms would perish and thus would not pass on this trait to further generations.) Notice that in this scenario the direction of reaction is towards the cause of the reaction (the vibrations), unlike all of the previous examples, which have been away from the cause of the reaction (a temperature change). In other words, it's attraction.
One of the important qualities of attraction is that it generally has to work over a distance. With attraction, you frequently have to start with a distance between the attractor and the attracted, with the attracted being impelled to decrease that distance. With repulsion, by contrast, distance may not already exist, with the dynamic being to create it - sometimes as quickly as possible (Think of the repellent force that you experience when you accidentally touch something that's extremely hot).
Notice that the attraction that I'm describing here between the vibrating organisms is a purely physical phenomenon, like everything else I've mentioned so far. It's analogous to the way that an iron nail is attracted to a magnet or that rain is attracted to the ground.
This power of attraction over distance may later have been an important quality in allowing organisms to expand their habitats into more complex and varied environments, allowing them to break out of the narrow confines of their single region of habitable water.
Imagine the following situation.
As I mentioned earlier, the relatively static environment of a stable layer of just right water in a pond is impossible to sustain for long. At the very least, convection currents would inevitably disrupt the equilibrium of the water, making some of the cells in it drift away from the comfort zone. There would probably also be the disruptive effects of occasional inundations of extra water as a result of, for instance, the tidal effects of the Sun and the Moon.
In these slightly more complex and dynamic situations the habitable zone may split into fragments (Figure 61) and an organism may easily find itself in a habitable pocket of water that's isolated from its main area of habitation. This pocket of water would be surrounded by water that's of an unsuitable temperature (being either too warm or too cold).
How could the organism get back to the main area of habitation again, bearing in mind that in order to do so it would have to cross this intervening hostile zone? The organism doesn't actually "want" to get back of course - in fact the organism doesn't care whether it lives or dies, being unaware that it's alive in the first place. However, getting back may have a useful consequence in evolutionary terms.
If the organism simply reacted directly to its immediate surroundings it would stay in its isolated pocket. This is because all of the processes at work within the organism would be repulsive forces that would ensure that it didn't actually move out of its mini comfort zone into the more hostile zone that surrounded it and that separated it from the main body of habitable water.
In order to "jump" across the hostile zone the organism needs a mechanism that overrides the processes of repulsion that are stopping it entering the zone. It needs a mechanism for reacting to the presence of its original habitable zone over a distance - a mechanism that provokes a greater reaction than the ones that would otherwise make it stay put in its isolated comfort zone.
Fortunately, the capability for reacting to vibrations, as described above, may provide such an ability.
The greater mass of organisms still within the main volume of the habitable zone will be moving around as usual and sending vibrations out through the water. For the isolated organism, these vibrations will stimulate it to move in their direction. As long as this attraction towards the vibrations from the main habitable zone is greater than the repulsion from entering the hostile zone the organism will be drawn out of its isolated mini comfort zone and across the hostile zone.
Provided that the organism isn't in the hostile zone long enough for major damage to be done to it, it will thus return to its normal environment unharmed.
This ability to traverse a less than perfect environment is a major advantage for an organism, allowing it to break out of the confines of its immediate, corralled surroundings.
With time, organisms would develop characteristics that allowed some of them to survive for longer periods in the hostile zones, allowing the organisms to occupy a wider range of habitats. As described earlier, these characteristics would be the result of random variations between organisms, and would only become standard features if they were useful. Such characteristics could be a thicker outer membrane or "skin", a greater ability to move, a different colour (allowing them to absorb heat to a greater or lesser degree) and so on. As a result of being able to occupy a wider range of habitats these organisms could find themselves in more complex environments where it would be advantageous to react in even more complex ways. Thus the complexification of life would continue apace.
In all of these examples concerning the manner in which simple organisms interact with their environments I've been careful to try to imply that the organisms simply react to their environment in an automatic way. They aren't truly aware of their surroundings in what we think of as a meaningful manner. How could they be? They possess no senses with which to be aware of their environments, as they have no sense organs.
Or do they? It's a fuzzy line when it comes to definitions, especially at the basic levels that are being considered here. For instance, I mentioned earlier that the outer membrane of single-celled organisms could vibrate when they were struck by vibrations travelling through water, and that the organism may then react to the vibrations. The whole membrane sounds very much like a full-body, cell-encompassing eardrum to me.
That means that at least on one level the cells can indeed sense vibrations. Whether or not this is a valid use of the term is perhaps open to debate - after all, does a thermometer "sense" temperature changes just because the mercury rises? (But then, thermometers are temperature sensing devices.)
