Sunday 7 August 2011

Evolutionary Noise

“Most species do their own evolving, making it up as they go along, which is the way Nature intended. And this is all very natural and organic and in tune with mysterious cycles of the cosmos, which believes that there’s nothing like millions of years of really frustrating trial and error to give a species moral fiber and, in some cases, backbone.”
Terry Pratchett
It is time for a thought experiment. Imagine a world where all possible variations of life exist already. In that world we have not yet created any obstacles or limitations. Life just exists and every part of it gets exactly what it needs to survive. This would result in a world where no part of life is more favoured than any other, and all combinations are as likely to survive. We would have what can be compared to a white noise, where every part of the life spectrum exists and is equally strong.

Noise will normally get shaped by different environmental properties. When it bounces somewhere or passes through something, certain frequencies are weakened or die out. The noise is filtered into something. Taking the idea of life as a noise a bit further, we can add filters to our constructed world as well. We can add constraints and obstacles that weaken or kill certain parts of life, thus forming it into a non-uniform shape.

Of course, real-world limitations are not as simple as having one filter shaping all life. For one, the filters will be changing between different geographical locations. There is also the fact that we do not have a static world, so the filters in each location will be changing constantly. An example of a short-term filter transition is the difference between night and day, while a long-term example could be continents drifting apart. Now if, in our sound analogy with an ever-lasting white noise, we would keep changing the filters for the sound, at some point all the frequencies would have been reduced to zero in strength. The same thing would of course happen with life, unless we introduce mutations.

Let us first change our one-dimensional life noise into a two-dimensional landscape, which has hills and valleys corresponding to where life is strong or weak (or even non-existing). There would be areas in this landscape void of life because of environmental filters. If a filter for such a region is lifted, the effect would still be visible afterwards. Now, because of possible mutations in life around the region, life from the outside can sporadically take root in the void area. When we remove a filter, life could slowly grow into that part of the landscape and cover it. There is of course the possibility of a big mutation skipping over a void region. Larger moves have a potential to end up in parts of the landscape where life did not exist yet, but can exist, but if these areas are very small it will be unlikely. This means that we will probably find islands of possible life that never get covered because there is no easy path through the filtered regions.

In the evolutionary approach, we would not have all combinations of life to start with. Instead we would start off with a very narrow peak in the landscape. Because there are already filters in place when life is started, it means that certain parts will be filtered already before anything exists there. Life will only be able to expand using certain open paths (or very unlikely jumps), and those paths can close or open again depending on the changing filters of the world. A region can be open for a while, letting life spread through it to another region, just to close and leave an island of life behind.

One can add more and more dimensions and add interaction between different parts of life (e.g. predator-prey relationships), to make this model more and more complex, but the simple case is enough to give us another viewpoint on evolution. What is the conclusion of all this? Not much. Sometimes looking at things from other angles can give you helpful insights. In other cases it does not, but at least gives you something to occupy your brain with for a while. Just as with life, human thoughts will keep spreading, sometimes mutating into blog posts like this one!

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