Quote:
Originally Posted by dreadgeek
Evolution is an elegant theory. By elegant I mean it in the way that mathematicians, engineers, scientists and hackers mean it--a solution that is subtle, powerful and no more complicated than it need be to do the job. On paper, it is a very simple theory. In practice it is fiendishly subtle. It also has very wide-ranging implications.
A few months ago, I read an article (that I wish I'd clipped to my electronic scrapbook) about farmers in, I believe, Alabama who were battling some pest or another. They were expressing surprise that this pest, which they thought some pesticide or another had all but eradicated, had come back with a vengeance and was now all but immune to the pesticide in question. This was, perhaps, the most poignant example of what not understanding evolution looks like. Evolution *predicts* that we should see exactly that kind of thing happen.
I'm going to terminate this post because I think that it might be interesting--and worthwhile--to post a general statement about evolution but that will take some time. Stay tuned.
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I normally don't quote myself but I wanted to have that above to explain why this subject came up. This is no substitute for reading a good treatment on the subject, but to understand why so many people get so mystified or flummoxed about people denying evolutionary biology on religious grounds, it's kind of necessary to explain why evolution is such a core part of modern biology.
Everyone is, I'm sure, aware that Charles Darwin is the name most attached to evolution. It's even called Darwinism or Darwinian theory. I won't belabor talking about Darwin there's plenty of good material on him. But what did he actually say. What follows is a condensation of a very subtle and elegant theory. I've stripped out everything I think is extraneous. But follow the logic and you will see why I call the theory subtle, beautiful and elegant.
Evolution in a nutshell:
1) Left to their own devices, meaning that absent predation or disease and with unlimited resources any population will tend to increase in a geometric fashion (e.g. 2, 4, 8, 16, 32, 64, 128...). As you can see numbers start to get really big really fast. If populations *actually* increased geometrically then we should not be surprised if the planet were populated by nothing but, say, elephants.
2) We don't live on a planet populated by nothing but elephants so there must be *some* check on the growth of populations. Those checks come in the form of predation, accident, disease and starvation.
3) Not every member of a population goes on to have offspring. This is because many die before they can manage to reproduce.
4) When sexual species reproduce the offspring is like but not identical to its parents.
5) If the parents have some trait that helps them survive a little better and they pass that trait on to their offspring, then they will survive a little better than those around them who may lack that trait.
6) Over time, these small, incremental changes in genes accumulate.
7) If a population becomes reproductively isolated and the environment is such that other adaptations may become advantageous they will tend to diverge from the founding population. If enough time passes then the two groups may not be able to interbreed if they come in contact later. They have become two different species.
8) Over very long periods of time, these accumulated changes are responsible for the diversity of species we see.
That is pretty much the theory in a nutshell.
I find it useful to invoke analogy so I'm going to ask you to come play in a toy world for a few minutes. In this world there are cats and there are mice. Let us call them average-cat and fast-cat. Let us say that, on average, for every five mice a cat goes after it gets two. That is average-cat's performance. Fast-cat, however, is a *tiny* bit faster than average-cat. She is able to catch three of five mice. Fast-cat and average-cat both get impregnated by the same Tom who also carries the gene that makes fast-cat a little bit faster than average-cat. But the gene is recessive. In order for average-cat to pass it on she needs a copy of the gene too but she doesn't have it. Her kittens will also be average. Let's say that the average litter size for these cats is four of which one kitten has a better than 50% chance of dying so the average number of kittens that live to reproduce is 3. Now, fast-cat, because she eats a little better than average-cat has five kittens. She also loses one of her kittens but that means she has four kittens instead of three. Let us say that of those four, they *all* inherit the gene for fastness. That means that, all other things being equal, the offspring of fast-cat will have more descendants than average-cat. Over time, genes for being a fast cat will become dominant in that population. This will now set the bar for the new 'average' cat.
Now, you might be wondering "okay, if this is true, Aj, then why don't cats move the speed of light". The reason is straightforward, after a certain point it just is no longer cost-effective to build a faster cat body. So cat speed is not being driven infinitely upwards. It's like the old joke about you and someone else running from a bear, the goal isn't to be faster than the bear, the goal is to be faster than the other person.
At the same time that the cats are spreading genes for being fast, the mice are in an evolutionary arms race with the cats. The mice don't want to be eaten, so any genes that help mice live a little bit longer so they can reproduce will, again, tend to become dominant in a species. If something changes for *either* mice or cats that effects how well the cats eat and how long the mice avoid being eaten, if it can be passed down it will be.
So, at some point, fast-cat winds up on an island where there are mice and birds. Average-cat stays on the mainland. Let's now introduce not just birds but coyotes. Coyotes go after cats. On the mainland it helps to be small so you can get up or in things quickly. Not *too* small but about the size of a house cat. On the island, however, there's nothing to predate on the cats. So they can start getting larger. At some point, a population goes across a river while it is dry and then it returns. Over time, the two cat populations diverge. One population becomes larger, the other population stays the same size. After a while, the larger cats begin to predate on the smaller cats because mice and birds just aren't cutting it for something the size of, say, a lynx.
That is evolutionary thinking in action. Does nature work this way? Yes. I built an overly simple toy world because the details are not important. It is just to give you an idea of what kind of explanatory power evolutionary theory has. Subtle, beautiful, elegant and powerful.
If we keep gaming out our toy world long enough to get a species that begins asking questions about the cats, at first glance it might seem incredible that something the size of a house cat gave rise to something the size of a mountain lion. It didn't all at once, but little tiny forcings due to conditions make it possible to grow a larger body.
Look around you. Look at your cats and your dog. Look at the plants in your garden. All around you are survival machines designed by genes.
Cheers
Aj