Rate of Genetic Change

This is a reply to Message 6652 at Yahoo's message board for the club.

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Originally posted by fasstedddy:
In other words, the explanation states there was adequate time for mutations to have produced the changes supposedly found in the fossil record, therefore the fossil record is explained as the result of the effect these mutations had on speciation verified by our time calculations. That is far from being persuasive. Benny could just as well be at Yellowstone Park.

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Henry Gee has just written an excellent book on just this question called In Search of Deep Time. At great length and detail (some might say greatly repetitive length and detail) he makes the point that in deep time (the full scope of time back to the origin of life on earth) there is no way to know with any certainty how any fossil relates to life-forms today. He claims that most information necessary to making such connections is now gone, having been eaten, buried, crushed, decayed, subducted, eroded and so forth. He says with fair certainty that most of life's history is forever unavailable to us, either no longer existent or so deeply buried as to have the same result.Paleontology is the weak science of biology, but it has by far the biggest cachet, with dinosaur fossil reconstructions the centerpiece and human origins the most significant sideshow. It also has had the advantage of featuring some of biology's most interesting personalities, from Cope and Marsh's dinosaur fossil wars of the late 1800s to the modern personages of Colin Patterson, Louis Leaky, son Richard Leaky, Donald Johanson, Stephen Jay Gould, Robert Bakker and Paul Sereno. All have given in to the temptation of speculating on the relationship of ancient fossils to modern life, and some have fallen over into the mistake of thinking that the speculation is in some way conclusive.The ephemeral nature of these speculations is obvious to anyone who has read Richard Leaky's books. Son of the once much more famous Louis Leaky he has become a respected paleo-anthropologist in his own right, but he has also been at the center of a virulent debate on human origins. After changing his mind many times on which fossil hominid remains lay on a direct line to modern humans he has lately become more philosophical. His books are the record of the changeable nature of such speculations. It seems that for him each new fossil discovery changes everything, and he is by no means alone in this. I use Richard Leaky only as an example of an inclination rampant in paleontological circles.Henry Gee has his own axe to grind. As a cladist (One who organizes things into categories, or clades, according to shared characteristics. A short note on pronounciation: the a in cladist and cladistics is short, while the a in clade is long.) he may feel a bit ignored since they receive far less attention than paleontologists more willing to walk out on slender limbs (that they often themselves saw off). He makes his point a bit stridently, though patiently, clearly and very repetitively. The point is that given the vastness of deep time there is no way to know if any particular fossil lies on a direct evolutionary path to any modern life-forms, including us, or how it is connected to other fossils of any age. The cladists, he claims, are the only group willing to acknowledge what is inherently unknowable and limit themselves to dealing with what is realistically knowable. That means looking at specific characteristics in great detail and classifying fossils according to degree of similarity into clades.The bottom line is that Henry Gee and the cladists agree with you. Just because sufficient time has elapsed for a fossil life-form to have evolved into another suggested life-form (fossil or modern it doesn't matter) does not mean that it did. Any speculation is just that, mere speculation.Where you and Gee may part company is in the conclusion. I may have read an insufficient number of your posts to have formed a clear idea of your position, but I will guess that you do not accept evolution. But to concede that the evidence necessary to any particular evolutionary conclusion does not exist is not the same thing as conceding that evolution itself does not exist. Gee believes that in most cases the evidence to demonstrate specific evolutionary pathways is absent, but fully accepts the theory of evolution, and is using his chosen science of cladistics to understand evolutionary relationships to the limits he believes possible.Gee's book was a fortunate find for me, for he gives voice to this issue that had been nagging at me for some time. Long-time participants at the Yahoo club may have noticed that whenever the discussion turned to human origins I suddenly went quiet (many probably thought this a good thing ). The reason was that though I could clearly see that, for example, Australopithecus afarensis shared many characteristics with modern humans, I couldn't see how one could on this basis conclude it was a human predecessor. To me it may or may not have lain on a direct path to us, but how could anyone know? Where was the additional evidence necessary for establishing that path? Conclusions seemed premature, yet great paleontological minds had issued tons of conclusions. My resulting confusions precluded my participation on this issue.But Gee has now made sense of the issues for me and enabled me to take a clear position. We cannot establish with any confidence most evolutionary pathways. The evidence is simply not there. But this fact has no negative impact on the theory of evolution itself.--Percy

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[This message has been edited by Percipient (edited 01-21-2001).]