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Darwin Posted November 28, 2000 Good evening, or perhaps good morning. I'm Tom Clegg and you're listening to Mostly Mozart. In the last three episodes, I've talked about psychology, electromagnetic radiation, and optics. Today, it's time for the fourth episode, and I have a little something to say about biology. I've never considered myself to be much of a biologist -- in fact, I always stayed away from biology classes in school, because I could tell they wanted me to memorize too many latin words -- but I do have a passing interest in genetics, and Charles Darwin's theory of evolution. One reason I like Darwin's theory of natural selection is that it is almost completely devoid of obscure technical details. For example, in order to understand it, you don't need to know the molecular composition of deoxyribonucleic acid, any more than Darwin himself needed to, back in 1859. I should caution you that reading Charles Darwin's book is a lot like reading Charles Dickens, although probably for a different reason. In short, it's got too many words. I'll just say that his idea was surrounded by a certain amount of controversy at the time. You could say he was writing defensively. The reason I'm talking about Darwin's theory today, is that I've heard so many people misusing evolution as a metaphor lately. There's nothing wrong with using evolution to mean change, or positive change,,, but you have to be careful not to attribute the outcomes of Darwinian evolution to any other process, merely because you have just referred to that process as a kind of evolution. All of this is off-topic, of course. The reason that I'm here is to make sure you get some Mozart every week. Today, I've got a guitar piece that claims to be the overture to The Magic Flute. And here it is. This is CJLY Nelson 93.5 fm. Mostly Mozart is sponsored by Comfort and Joy, a unique children's store. --- That was a guitar arrangement of the overture to the Magic Flute, performed by Daniel Cox. I was thinking of doing a whole show of guitar music today, but Mozart never wrote any. So I'll have to stick with another popular stringed instrument: the pianoforte. Pianoforte is an Italian word, or maybe I should say two Italian words; I suppose the English translation would be Softloud, which doesn't have quite the same ring to it. I suppose that would explain why we just call it a piano. In any case, for those of you who haven't seen one, a Softloud, or piano, is much like a harpsichord, except that it allows the player to control the loudness of each note by pressing the keys harder or softer. If you've ever used a good electronic keyboard, this concept will seem familiar. And now for something you might not already know: I have a whole bunch of different recordings here of Mozart piano sonatas. This next piece, ...is one of them. --- Ici Say Jee L Egerec, quatre-vingt quinze virgule cinq, fm. You're listening to Kootenay Co-op Radio. I'm Tom Clegg. Mostly Mozart is sponsored by Comfort and Joy, a unique children's store. I said earlier that I was going to talk about Darwin's theory of evolution. Stay tuned, and maybe I will. --- OK, I finally have something to say about Darwin's theory of evolution. Before I describe Darwin's thesis and the way he argues it, the historical background is somewhat revealing. In the few decades before Darwin wrote his famous book, a geologist name Charles Lyell was arguing that we must study geology under the assumption that things work today the same way that they have always worked. We won't get anywhere with science if we explain our world by inventing unusual kinds of events which are supposed to happen in the past, unless we can see them happening in the present. I think the fancy word for this idea was "vera causa", which would be latin for "true cause". See? I haven't even started talking about biology, and already there's latin. Lyell's work was a direct inspiration to Charles Darwin. In fact, Darwin's first published paper was an application of Lyell's principles to explain unusual shapes of coral reefs. Getting right to the point now, Darwin's theory rests on three assumptions. They are: variability, inheritance, and the struggle for existence. Variability refers to the fact that individual members of a species are not always exactly alike. This was well known to any farmer or breeder in the 19th century. The biologists, of course, were busy arguing about whether God had made everything perfectly to start with, and if so, whether mutations and hybrids really exist and whether they should be allowed to reproduce. Inheritance is some mechanism by which children tend to be like their parents. Again, this was obvious to everyone in the 19th century. They didn't know how or why children tended to be like their parents, but they could tell that it was happening to themselves, and their plants, and their animals. The third assumption is the struggle for existence. This follows directly from some simple math. Darwin calculated that a single pair of elephants, which are the slowest breeding animals on earth, would grow to a population of 19 million in the space of only 750 years. Human populations double in about 25 years; at that rate, in a thousand years, we would cover the earth standing shoulder-to-shoulder. The same argument works for any life form. Obviously, 1000 years have passed, and the earth is not yet full. This means that there must be some force at work to reduce populations. Once again, you don't have to know what that force is, in order to see that it must exist. The theory of natural selection is that some of the variations between individuals are inherited by their offspring, and that some of these inherited characteristics give some individuals a better chance of survival, in a world where not everyone can survive. I think we'd all be better off if we knew that theory forwards and backwards, so I'll say it again backwards. Our world is of finite size, which means that not every living thing can survive long enough to reproduce. Some individuals have a better chance of surviving than others, simply because they are not all the same. Some of these differences are inherited by their offspring, and this has the effect of making those survival characteristics become more prominent in the species as a whole. Discussions of evolution often use the term "adaptation." This is a natural term to use for beneficial inherited characteristics, but it also brings up a common point of confusion. The adaptation of a species to its environment does not arise from the adaptation of an individual to its environment. In fact, although Darwin could not have known this, there is only one opportunity for new heritable characteristics to arise, and that is during the combination of two DNA molecules during reproduction. These days, biologists are quite certain that inheritance of acquired characteristics does not happen. If you get really good at chess, for example, you cannot pass that ability on to your children genetically. So, to sum up: Darwinian evolution happens when random individual variations are inherited by future generations. These variations give some individuals a better chance of survival than others. Natural selection is the process by which "good" random variations become more common. This is "survival of the fittest." Why was Darwin's book called, "The Origin of Species?" Because the fittest individuals always totally overwhelm the less fit individuals when they are competing for the same resources, and this explains a long-standing mystery: If we have so many random variations, why do we only have a finite number of species, each one containing individuals who are very nearly identical? Well. That's the biology lesson. I'm Tom Clegg. Mostly Mozart is sponsored by Comfort & Joy, a unique children's store. Today is the internationally unrecognized piano day; here is Christoph Eschenbach. Thank you for listening. |