Wednesday, April 4, 2012

Evolution: The fitness landscape

Since I often read/hear incorrect perceptions of evolution which often causes people to misunderstand it. Giving evolution a goal, or an end result is a quick way to misunderstanding.
A very good way to think of evolution is “fitness peaks”. The best way of explaining this is that an organism (or a cell, or a protein, or even a molecule) has a certain amount of fitness in its environment. As a change occurs in the organism or structure, the placement on the fitness :landscape: will change. Imagine a plain, stretching out forever, and in this plain there are small bumps, hills, and a few mountains. Each of these hills and mountains represents a relatively higher amount of fitness compared to the flat plain. In an environment of water, an organism with fins will be at a hill or mountain, where as an organism with stumpy legs will probably be in a valley.
Evolution is driven, remember, by mutations, and mutations, in most aspects, are random. They are caused by radiation, and environmental influences, and sometimes simply just happen due to chance. Since this is random, we can imagine that our organisms, while undergoing certain mutations bounce and skip around this landscape. Sometimes they will go down hill, sometimes they will go up hill, but the ones that are uphill will usually have offspring that are close to the hill, and thus hills will most likely always be populated. However, once in a while, an organism can live in a valley (although perhaps difficult), but from the valley, new hills and mountains can be reached. And so evolution progresses. Humans, with brains, thumbs, eyes, ears, nose, and mouth (amongst other amazing features) are on a mountain. A very, very high mountain.
The thing with these fitness landscapes, however, is that the environment creates hills and valleys. So what was once a mountain (fins in an ocean) can turn into a valley, if say a lake dries up. Fitness landscapes also change in the predator-prey (and subsequently parasite/host + synergistic relationships). A cougar that suddenly gains great night vision will cause the deer’s relative hill to become a valley.
To make evolution more difficult, some organism mutate faster than others (for various reasons, some unexplainable). This puts a whole new spin on evolution – there is the possibility to gain the ability to change (subsequently evolve) more often – this can also cause a fitness landscape to be volatile, creating scenarios where there are no mountains or deep gullies, but nearly all foreseeable changes do little in the way of evolution.
I hope this helps understand evolution a bit more.
Real evolution has no end, no goal. The fact that we see “survival of the fittest” does not mean that changes in the genome tend to be more beneficial to organisms, statistically speaking, I’ll assume that it is quite the opposite.
At any rate, please view evolution objectively. There is no “line” of evolution – there is no thing that evolution tends to go to. Rather, it is survival, which is correlated, but not connected, that has a tendency to choose directions.

[[This post was slightly off the main vibe of my site, but it is one of my pet-peeves.]] Have fun out there!

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