Originally Posted by winwin
As an illustration, the hairy mammoth in a tropical environment would experience evolutionary changes NOT in a random direction, but in a direction polarized by the effects of a tropical climate on what had previously been a creature of the colder regions.
Not random at all, no sir, structured, not random.
Don't let the beauty of the result change your view of the cause.
The "random changes" bit is simply the $25 phrase to explain why some of us have dark hair when both our parents are blonde, or why some of us are taller or shorter or more muscular or thinner.
Let's take your wooly mamoth in the heat example.
Two mammoths find themselves magically put into a 110 degree jungle. They have kids. Of these kids, some of them have longer hair, some of them have shorter hair, some of them have similar hair (random changes, just like two cats can have a litter of kittens that look nothing like each other or the parents). Lets say this first generation of young has hair lengths of 8,9, and 10 (short, medium, long).
Those mammoths with shorter hair will be healthier (for obvious reasons), and so will live longer and breed more. thus, the second generation will be bred from shorter-haired parents. the process repeats. the second generation has a random mix of shorter, longer, similar hair lengths, but because of the shorter-haired parents the short/medium/long will be lengths of 6,7,8 (random numbers, you get the point)
again, the shorter haired ones are healthier and breed more, and the next generation is maybe 4,5,6.
eventually, you've got bare-skinned elephants like we have today.
You can see the same thing in farming. Farmers like tall corn, so they breed the tallest stalks with the tallest stalks, and get taller stalks.
You can see the same things with dogs and cats. Ask any breeder on this board and they can give you an in-depth explaination of how to alter a species of cat to enhance or remove a genetic trait.
(AH HA! I hear you say. That's what I mean! the change in dogs and cats is guided!)
The breeding is guided by the breeder, just as the survival of our long-haired mammoths was guided by the heat, but the changes are still random. A breeder who wants to breed all-white cats must wait until they can find some randomly mostly-white cats, and them breed them to make some randomly even-more-mostly-white cats, until after some generations you have pure white cats (except for the random ones that aren't.)
The change over time is guided by the environment and the species's "fit", but the changes are still random. It appears like a perfect fit to us because we didn't see the millions of years of evolution, we only see the end result. it's only our insignificant lifespans that give the illusion of perfection and planning.