PereGaea

Laslo Godel

1: PEREGAEA

We often like to ask ourselves questions like: `How did this Universe begin? Or even: `Who began it and why'? `What was the very first Cause with which all its Causes and Effects began?' `What was before that?' Unfortunately it is unlikely we shall ever know the answers to any of these questions. Even if we ever thought we did, how long would we continue to think we did?

Whatever Caused the beginning of the Universe, it wasn't the only Beginning it has had. Somewhere, probably entire billions of years before the Earth was born, another Beginning almost as momentous as the first happened. This was the advent of a new form of Cause and Effect, Stimulus-Response.

What do we mean by Stimulus-Response? Cause-Effect is usually applied to passive objects which can only interact with others through brute physical or chemical strength. Stimulus-Response on the other hand relates to dynamic objects. These interact with other objects by temporarily altering their shape in some way, by moving toward or away from them, by exuding some substance which must be regenerated over time, or ingesting an object to replace energy or matter which has been lost. Whether or not such objects can be said to be `alive' is not a question that will concern us here.

Where might the new Beginning have happened? I will not attempt to speculate on that either. It might have been on or in a planet somewhere, but it could just as easily have been the inside of an interstellar dust-cloud, or even a star. To keep my story simple though, let's assume that it happened on an Earthlike world, indeed we'll give this world the name `PereGaea'. This means I can use organic terms where necessary to make things a little easier to follow, as well as a few from the worlds of electronics and computers

We will also assume that PereGaea has just produced its first self-replicating dynamic object, and that it arose in one of its oceans. But since we don't really know what kind of world it exists on or whether it is alive, we will call it a `dynamism' rather than an `organism' - or just `dynism' for short. This dynism possesses a single sensor that enables it to detect some specific change either in itself or its environment, and a single effector that enables it to respond to that change in some specific way.

Billions of these dynisms now appear. However, although their reproductive mechanisms, whatever these may be, operate perfectly most of the time, we will assume that errors occasionally occur that allow mutations to arise. Only a few of these mutants will normally survive, but enough do to allow our primitive dynism to eventually diverge into different species. These at first compete solely against their environment, but as their numbers grow and put pressure on even PereGaea's vast resources, they will come to compete against each other. Some species will be more successful than others in the way they exploit this situation. Indeed it seems reasonable to suppose that one such species will seldom be fed upon, one will be fed upon by virtually all other species, while the rest will spread out along a Gaussian Curve like the one below. PereGaea has acquired its first Predators and Prey.

In time the dominant Predator will be displaced by a successful mutant which has evolved new and more efficient sensors and effectors. This will in its turn eventually be displaced by an even more efficient predator. Rather than give each such predator a new name each time it arises though, we will just keep on calling it a dynism, no matter how big and complex it might become, though we'll grace it with a capital `D'. This will make it much easier for us to trace the path of evolution on PereGaea.

Let's start out on that path by imagining that our simple Dynism has now passed beyond the `drifting spherical cell' stage and acquired a flagellum made of some resilient material.

It's single sensor (the red circle) does not, as you might imagine, detect stimuli from its environment, but from its own body. It simply detects when the flagellum lies either directly behind the Dynism or to its right.

It then causes a fibril-like effector (the blue square) to bend this flagellum towards its left like this.

Although the sensor turns the effector off when the flagellum passes through the centerline, the flagellum's momentum carries it on until it has bent as far as it can to the Dynism's left.

Its natural resilience then causes it to flick back towards the Dynism's right. Again its momentum carries it through the centerline.

The cycle then repeats. This crude but simple `reflex arc' is enough to propel the Dynism around PereGaea's Ocean where it may blindly bump into enough food to maintain its existence.

Let's imagine now that these Dynisms reproduce by fission. In some cases however the process doesn't quite complete. Siamese twin-like, they have two joined bodies and tails.

Most such mutants will die near-instantly. A few however will eventually arise with two halves that are mirror images of each other in function as well as appearance. The two reflex arcs in such a Dynism will work in alternation so that, when one sensor causes its fibril to contract, the other causes its to relax. If the flagellum lengthens to become resonant with the fibril-switching frequency, its resilience can then amplify the effect of this `reflex loop'. Since this Dynism will be able to swim faster than its predecessors, it should bump into more food and have a good chance of surviving to reproduce its own kind. That is of course if it can reproduce in this new form, but if it can't, the evolutionary `experiment' will simply repeat time and time again until it can.

Once it finally succeeds, this new species of Dynism can then take its next major Evolutionary step. When an individual fissions to reproduce itself, it occasionally happens that one of its components fissions twice so that its offspring acquires two of them. Provided this extra component does not interfere with the operation of others it should do no harm. If it is a flagellum position-sensor for instance, it should not switch an effector off when another switches it on.

Although such `spare' components are likely to be of little use to individual Dynisms, they are of major value to the species. This is because they will inevitably mutate into other forms in successive generations of Dynisms. Indeed, it is by this means that the Dynism now acquires the first of its sensors that enable it to respond to environmental stimuli. Evolving from an extra pair of flagella position sensors, these respond to light instead. They act to over-ride the normal position-sensors by only allowing them to operate when they detect light above a certain threshold of intensity. Here I've represented the reflex loop with a pair of rectangles.

As you can see, if the Dynism's left-hand `photocell' registers a well-lit region of Ocean, which we'll assume contains more food than darker regions, the Dynism will turn left towards it. When this turn exposes both photocells to the light, the Dynism will stop turning and swim straight ahead towards the lit region.

If the photosensors eventually migrate to the front of the Dynism, its ability to find light patches of ocean will not only improve, it will also become able to avoid dark ones. These may be occupied by rocks or other solid objects, perhaps even Predators.

Could the Dynism evolve the same behavior if its light-sensors turned their halves of the swim reflex off in response to bright light instead of on?

Clearly the connections would have to be rearranged. But rather than look at how, let's instead look at a related but more important problem. We'll need to go back for a moment to our original unbifurcated Dynism. At this stage in Denarian evolution, the optimum connections between sensors and effectors can only be made through the process of mutationary trial and error. But will this still work when, as it surely must, the Dynism acquires several sensors and effectors? Then, as their numbers increase arithmetically, the numbers of possible connections between them will increase geometrically.

Such a `hardwired' Dynism will eventually be superseded by one which can connect its sensors to different effectors according to whatever environmental situation it finds itself in. This Dynism evolves a kind of central `switching center' through which all these connections can be made or broken as required. Evolution may then act on this switching center more quickly than on direct connections.

Let's look inside this `comparator', as we'll call this switching center, to see how it might work. As you can see in this drawing, two sensors can together assume four states: both on, both off, one on and the other off, the first off and the other on. The same of course applies to two effectors.

Imagine now that the comparator can construct an `input pattern' that represents whichever of these four states it sensors may be in. It then compares this pattern to each of a set of `templates' stored in a `memory' of some kind, trying each in turn. Attached to each of these Templates is another two-square pattern. When the Comparator locates a Template that matches the Input Pattern, this second pattern is then used to determine which of the two effectors is switched on or off. We'll call this pattern an `output pattern'.

However the actual Output Patterns need not all be different from each other; the contents of the Comparator's memory may well look like this. This is because a Dynism might need to make the same response to two different stimuli, for example two different kinds of food object.

Now, when a Dynism replicates, errors may cause successive offspring to not only acquire `spare' sensors and effectors in the way we saw earlier, but increase the size and number of Sensor-Effector Pattern `Pairs' in their Comparators to accommodate the new linkage possibilities.

Where everything is simply duplicated, no harm is done. When the Dynism's Comparator attempts to match an Input Pattern to a Template, it need only look at each Template-Output Pattern `Pair' in turn as before and copy the Output from the first match it finds to the effectors.

Dynisms will however, over successive generations, inevitably produce descendants with `flipped' squares in either their Templates or Output Patterns. Since this has the effect of linking sensors with effectors in a new way, such mutations will almost certainly be as lethal as any mutation in the Dynism's body components. A mutant may arise for instance that turns away from bright patches and swim at its fastest rate only in total darkness. But just occasionally, as with a bodily mutation, some new Template-Output Pair will prove beneficial to an individual. If that individual then survives long enough to reproduce, that Pair will come to benefit the species.

How do mutant Pairs affect the matching process? If the Comparator happens upon a tried-and-true Pair for matching before it can reach its mutated twin, then no harm will be done. If it reaches the mutant first, only then will the Dynism's existence be put at risk. Let's assume for example a Dynism has four offspring each with four memory pairs, one of which is mutated in each case. As you can see here, two will survive and two will not. The third offspring survives only because the mutation, even though it will always be selected before its normal twin, turns out to be favorable.

Why should the Dynism rely on this slow hit-and-miss process of Evolution to improve the quality of its Pairs? Why can't each individual Dynism create an Output Pattern at random for every Input it extracts? If it proves beneficial, the link between the two patterns could then be made permanent; if not, the Comparator would try another one. Even if most such `experiments' prove fatal and few such Dynisms survive, they could offset their losses by stepping up the rate at which they reproduce themselves.

Such a `RAM memory' system will eventually evolve, but our Dynism must evolve several other capabilities first, so we will need to come back to this later on. In the meantime, Random Mutation serves as its `RAM'; birth, life and death the means by which this is written to, read, and erased. Natural Selection becomes the vital `rachet' which preserves successful `experiments'. And together they become Evolution which, as we've now just seen, acts on PereGaea's acts as well as its actors.

What happens when Dynisms grow to acquire more sensors and effectors? With sets of four sensors and effectors, sixteen different patterns are possible; with eight such sets, 256; with sixteen, 65,536. As you can see, as the number of sensor and effectors increases to x, the number of possible Pairs rises to 2 to the power of x. With just 64 sets of sensors and effectors, this number reaches two to the sixty-fourth power, or nearly two times ten to the nineteenth. Even if a Dynism only needs a tiny subset of that vast number of Pairs to survive, won't the matching process still take a very long time indeed if its Comparator can only match one Input Pattern to each Template in turn?

On PereGaea as on Earth, probably the only way to overcome this problem is for the Dynism to evolve some form of Parallel Access memory. Consider looking for a piece of music on a cassette tape or CD. On a tape you may have to look through its entire length, this is `serial access'. With a CD, the pickup laser can move across the disk to find it very quickly indeed, this is `parallel access'. The most favored technology to enable Parallel Access memory on Earth are Neural Nets. But these may not be the only Nearest Template matching systems that can arise on PereGaea, others may predominate through Natural Selection like everything else.

The time it takes a Dynism to `convert' a stimulus into a response incidentally may well the only way we can define any sort of `time interval' on PereGaea. The length of this Interval is in turn determined by the speed at which fundamental physical interactions take place in PereGaea's environment, whether they be inertial, chemical, electronic, or something beyond our power to imagine. Many of these will in turn ultimately depend on macro-scale things like PereGaea's size and mass, the corresponding strength of its gravitational field, and even the spectral type of the star it orbits.