janc@uofm-cv.UUCP (10/28/83)
Quoting Ray Davis: > I always wondered where the fossils of the transitional creatures > went. You can find lots of prehistoric monkeys, lots of cavemen, > and lots of modern men, but where are the fossils of the creatures > that slowly evolved from one step to another. I think I can clarify this a bit, but first I should point out, that the details on how specization happens are currently hotly debated among evolutionary biologists. It is generally accepted, however, that the new species only develop only under very special conditions. You don't have to be an expert in evolutionary science to be able to see that a new species can only develop when: (1) A population is isolated which is neither too small to have the necessary amount of natural variation, nor too large for changes to spread through the population. (2) There must be conditions which place the population under enough stress so that modified individuals have a significant advantage, but not under so much stress that the population is wiped out. Naturally, such a situation rarely arises, but when it does, change proceeds (in an evolutionary sense) fairly quickly. The result is that evolution does not happen slowly and continuously. Instead, species stay unchanged for long periods of time, then, when the right conditions prevail, they change comparatively rapidly. Now consider the fossil record. From the period when men were evolving from ape-like forms, we have fossils from maybe a dozen sites, randomly scattered over a period of millions of years. The odds are very small that we would see a transitional form, since they aren't around long, and are confined to limited geographic regions in small populations. Imagine an analogy: I mount a camera over your terminal, and take a ten pictures at random intervals over a year. I get pictures of you, and I get pictures of your empty chair. I'm not likely to see you getting in or out of your chair. I can conclude that you don't customarily spend two or three hours inching into your seat. But can I conclude that you appear there every morning in a *PUFF* of smoke? Though I can't disprove that theory, I'd need much more finely spaced it. Both a theory of continuous creation (God make a new species every now and then) and evolution are in agreement with the human fossil record. However, I believe there are examples of the kind of evolutionary change I have mentioned in the case of bivalves (clams), from regions where there is a more complete fossil record. Jan Wolter University of Michigan Ann Arbor Michigan