04-19-2004, 10:09 AM
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#1 (permalink)
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Wehret Den Anfängen!
Location: Ontario, Canada
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A very good description of evolution
From another e-community:
Quote:
Five fresh fish typed:
The following is my attempt to condense all of evolutionary biology into a few short and simple paragraphs.
The driving force for evolution, and all life, is the information contained within the genes. Information not only wants to be free, it wants to propagate itself.
Those genes that contain information that better propagates are genes that will come to dominate the scene. This is evolution in its raw form: the distribution of winning information.
From this point of view, then, trees are not actors in this play. They are passive mechanisms controlled by the genes.
One should not be asking how such-and-such benefits the tree. The tree is irrelevant except insofar as it serves to distribute the genes. If the genes were to mutate in such a way as to permit a better way to propagate themselves, we'd see an end to trees.
There is a key constraining factor, though: of all the infinite variety of ways a gene could propagate itself, only a few are truly viable. One can imagine this as "islands" of reality in an infinite sea of possibility.
The islands are, from one angle, the types of life we know of. From another angle (perhaps there are lakes on these islands, with islands in the lakes, with lakes on those islands, ad nauseam) they are Kingdoms, Divisions, Phylum, Classes, etcetera.
A single gene may be able to influence the viability of its lifeform within the constraints of its island. It is exceedingly unlikely, ie. impossible, that a single gene can be responsible for shifting its next-generation lifeform from one Class to another, for instance: there's an entire ocean of "impossible non-reality" between those two islands.
But within its "island" -- which seems to me to correspond roughly to our concept of "species" -- the gene can influence the likelihood of its successful propagation.
A gene that makes an apple taste a little sweeter may make it more likely that this gene is propagated to the next generation. At the same time, making the apple taste sweeter comes at a cost: it takes energy and perhaps increases the likelihood of rot or some other form of failure.
Consequently, genes generally achieve a balance between increased propagation of the gene due to favourable effects and decreased propagation of the gene due to undesirable effects.
With the exception of radical mutation the information within genes changes very little between generations: it is an incremental process, with each combination of new genes being either very slightly "better" or "worse" at continuing the propagation of their information.
Most of the time this balance works out to be "good enough": while a radically super-sweet apple might prove to deliver the maximum probability of propagation, the small changes between generations that would lead from our current crop of apples to this super-sweet result are not so significantly "better" that natural propagation will "prefer" the "better" apple to the "worse" apple in any significant way.
There are a lot of "quote" marks in the previous paragraph, because those words tend to be loaded with meaning that is not entirely appropriate to a discussion of evolution. The words "better", "worse", and "prefer" tend to bring to mind an outside judge and controller of evolution.
Nothing could be further from the truth. Natural evolution is strictly mathematical in nature, no more judged and controlled than a weighted die that tends to roll sixes. It's a matter of statistics, of probability: that which tends to happen, tends to happen more.
The "better" genes are those that tend lead to further propagation of those genes; the "worse" genes are those that tend to reduce the likelihood of propagation, and evolution only "prefers" the "better" genes because they are statistically more likely to be propagated.
And so we conclude: the reason fruit trees make fruit is because the information encoded within the seed has, over time, had better chances of propagation when the lifeform it creates takes the form of a tree that bears fruit. At this late stage of the evolution game for trees, it appears that fruit is "good enough" for now.
A rather circular argument, I know, but that's how it works.
NB: this post is informed by the writing of Richard Dawkins. YMMV, particularly if you have been informed by competing evolutionary biologists.
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http://ask.metafilter.com/mefi/6072#126025
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Last edited by JHVH : 10-29-4004 BC at 09:00 PM. Reason: Time for a rest.
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