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the wonders of nature never cease ! (long)
Chuckles · 10/19/02 at 1:33 ET
I agree, we love to tell stories that make things sound much simpler than they really are. It's our nature. The physics of three bodies interacting is a really complex problem. And biology is infinitely more complex than physics. Do the math. There is nothing simple about the origin or perpetuation of living things, it is a grand and miraculous panorama that we will never completely be able to understand. Science is about looking for little hinges that open big doors to discovery. Not about answering everything by waving it away. That's something we just do because of the way we are. Newton spent most of his time in Biblical exegesis and alchemy. He was a deeply spiritual man of his time. But he also had the time to come up with a new way of calculating and a way of describing how things move, and those things turned out to be so useful that most people associate him only with those things. With a couple of equations, he showed how the movement of nearly anything can be predicted under limited conditions. It doesn't sound like much now, but it was such a big deal then that Europeans spent the next couple of hundred years getting excited about it and thinking they were going to probe all of the mysteries of the universe and solve all the problems of humanity by applying this new mode of reasoning rather than relying on the stuffy classics that were once the sole education of even the most literate. Newton's little hinges of The Calculus and the laws of motion opened the door to a swell that changed all our lives, both for the better and for the worse. Darwin's little hinge was natural selection, and the big door was nothing less than a mechanism that could explain the way that the form and function of living things could change over time. But it was based on a very unique way of looking at nature. Darwin saw nature in terms of its variety rather than its well-classified families of organisms. Where others saw a few different finches, Darwin looked more closely and saw that every bird was very slightly different in its own way. And yet in each area, there were birds that were very similar living together. Darwin carefully observed the beaks of finches and how they were so well suited to the geography where the particular variety of bird happened to live. The wheels in his head turned. How did the beak happen to get that way in those birds ? Why was each bird so slightly different, if God had made them that way to be best suited to the food placed there for them. Sure, God did it. But how ? What means did She use ? Darwin read a guy named Malthus who had some bizarre idea about overpopulation and how some people lived and some died when a population was no longer supported by its resources. Darwin thought about this. And he thought about the beaks. And it came to him. One of those thoughts that you get every now and then that just seems to make sense of a whole bunch of other things, but you can't quite see how it could be right. It's just too simple. If every bird that was born was very slightly different from every other bird, then every now and then there should be one with a slightly better suited beak for the kinds of food in that area. If more birds were born than could survive, which seemed to be the case in general, then of course some would live and some would die. Which ones were more likely to live ? A slight statistical advantage at least should go to the ones with the beak variation that was very slightly better for the food in that area. And when they mated, they would sometimes give their slight advantage to their children. So a tiny inheritable change in the beak of a bird that was helpful should spread through a population as they reproduced. It's a tiny effect, it should take a long time to spread, it requires living things to be very richly varied as they reproduce, and it requires that more living things consistently are born than survive. But in the unlikely event that these things were actually true, what an idea this was. It could potentially explain not only the distribution of finches, but maybe of all other varieties of living things. If tiny changes can accumulate to make better suited beaks, why can't they accumulate to the point where we get a whole new species ? If the process worked, what would stop it from continuing on ? If it was that powerful an idea, maybe it could explain the apparent waves of Creation in the fossil record, and even the way living things are grouped into families ! It was the first time (though it was discovered in parallel by someone else) that anyone had ever come up with a way that *could* work that explained the various data from the different fields and could be made into scientific terms that would be able to form predictions, at least in principle. And as we learned more about cells and anatomy, it came to explain more and more of what we saw rather than less and less. As unlikely as it seems, the little hinge turned out to open an enormous door. Even some of the assumptions he wasn't sure about turned out to be right, though it took until the wider discovery of Mendel's experiments with peas to figure out how Darwin's theory could possibly work. Darwin couldn't figure out how his scheme could work because the good traits that appeared should blend in with that of other individuals they mated with. What would allow the tiny good new traits to persist discretely ? The discovery of genetics gave the answer, living things inherit discrete versions of traits because there are discrete variations on the same gene. So inheritance doesn't blend out the useful new traits, they are preserved intact in each successive generation. If this account seems improbable to you, then good. It certainly doesn't explain by itself the origin of life nor is there any superficial or easy connection from natural selection to the major transitions of the fossil record. Those are other questions, and ones we may never have a complete answer for, though part of that may just be that we can't go back to see exactly what happened. We have guesses, but no one has ever produced a living cell from inorganic parts the way we have observed new species forming from others. We have to guess at the kind of selective pressures that might have led to particular new variety flourishing in some ancient population. It's a fascinating study, but a difficult and often imperfect one. And who knows if a new hinge will come up that helps, or whether some things will forever be a mystery. It's usually a good thing not to take improbable ideas on faith. There's plenty of science I don't believe either. Believe whatever makes you happy. The example of the giraffe is usually used to illustrate Lamarck's theory of adaptation. Lamarck observed the same remarkable fit of organisms to their environments that others like Darwin obseved, and tried to explain it. Lamarck theorized that giraffes tried to strrrreeeetttccctttcccchhhhhhh to reach higher branches, and that their necks got a little longer as a result. The next generation, he concluded, inherited that longer neck as a result. He turned out to be wrong, oh so wrong, we discovered through both our breeding of plants and animals and our discoveries of genetics. If he was right, we would probably be speaking Russian now. But that's another story. Things don't generally inherit traits that they acquire during their lifetime (except possibly in certain cases of bacteria, though that is controversial). Whatever we inherit genetically has to be the results of how the genes of our parents shuffle together and whatever mutations might have occured in our parents reproductive cells. Things they learned or abilities they acquired in their lifetime can't be inherited genetically, only culturally. That's why explaining adaptation (goodness of fit of organisms to their environments) is so difficult without the concept of selection operating over a population, or else just assuming that God plopped things down where they belong during Creation. As for whether the whole thing is random, I agree with you there too. It obviously isn't random. The reason "randomness" is emphasized is partly technical and partly ideological. The ideological part is of course the idea you brought up, that the whole thing is naturalistic and can't rely on a Great Designer or Watchmaker if it is to be scientific. The technical part is to emphasize that we've given up on Lamarck's theory of inheritance of acquired traits in modern genetics, and that the theory of change in populations doesn't require that nature know ahead of time what new variations to produce in order for the process to work. This is different from the ideological reason, because it doesn't reject the idea that nature can have forethought, it just doesn't require it. It is the philosophical requirements of naturalism and mechanism that make teleology, or planned forethought, a cheating move in scientific theories. The technical requirements of the theory just demonstrate a mechanism for change to propagate. yours respectfully, Chuckles
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