| Feature Article - August 1997 |
| by Do-While Jones |
The main reason we bought Ian Tattersall's book, The Fossil Trail, was its subtitle, "How we know what we think we know about human evolution". We are sensitive to criticism that we don't portray the evolutionists' positions correctly. We thought this 1995 book (written by the Head of the Anthropology Department at the American Museum of Natural History, who is also the Curator in Charge of the Hall of Human Biology and Evolution) would be an authoritative explanation of the evolutionists' current position on human evolution.
Chapter 16 ends with these words:
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As I said right at the beginning, what we think today depends
very largely on what we thought yesterday. If the entire human
fossil record were to be discovered tomorrow, and studied by experienced
paleontologists who had developed their skills in the absence
of preconceptions about human origins, I am pretty sure that (after
the inevitable bout of intellectual indigestion) a range of interpretations
would emerge that is very different from those on offer now.
With this caveat, then, let's go back to the basic fossil evidence of our own origins and emergence, bearing in mind our historical interpretive burden. We all want to know where we came from; and knowing where received wisdom colors our perceptions of our origins may help us to approach this question a bit more dispassionately. 1 |
Tattersall is remarkably candid when he explains how fossil remains are interpreted.
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Eventually I plucked up the courage to ask a distinguished scholar
the crucial question: How does one study fossils? How does
one understand what they tell us about the history of life? The
answer? "You look at them long enough, and they speak to
you."
Nowadays I realize that this response has a great deal more merit than it would appear to on the surface. ... Well, despite my disappointment at the time I'd nowadays be the last person to dispute the importance of intuition in science; for there's no doubt that it stands as the very foundation of scientific creativity. 2 |
Based on this intuition (that is, what he hears the fossils telling him), the scientist creates a scenario describing how things came to be the way there were found.
| ... the average scenario is a highly complex mishmash in which considerations of relationship, ancestry, time, ecology, adaptation, and a host of other things, are all inextricably intertwined, tending to feed back into each other. When you're out there selling such complicated narratives, normal scientific testability just isn't an issue: how many of your colleagues or others buy your story depends principally on how convincing or forceful a storyteller you are--and on how willing your audience is to believe the kind of thing you are saying ... 3 |
In other words, the commonly used technique for establishing the a theory of human origins is "proof by intimidation."
Most people think that fossils are the strongest argument in favor of the theory of evolution. In fact, the fossil record contains a very strong argument against evolution. That's why the scientists who study fossils were among the first to reject the neo-Darwin synthetic theory of evolution. Tattersall himself, along with paleontologists Niles Eldredge and Steven Jay Gould, developed the theory of Punctuated Equilibrium.
| For years paleontologists had labored mightily to fit the evidence provided by their fossils into the framework of stately change dictated by the New Evolutionary Synthesis; and by around 1970 some of them were coming to find that fit increasingly uncomfortable. The Synthesis, as you will recall, elegantly explained all evolutionary phenomena in terms of the gradual accretion of genetic changes in evolving lineages, all under the guiding hand of natural selection. In turn this implied that species, while discrete units in space, should lose definition in the dimension of time. Species were, in fact, viewed as nothing more than arbitrarily defined segments of evolving lineages which, if they didn't die out leaving no descendants, would inevitably evolve into something else. Time and anatomical change were thus thought to be more less synonymous. The implication of this was that the fossil record should consistently show smooth intergradations from one species to the next; inconveniently, however, it too often didn't. Species, it has turned out, tend to appear rather suddenly in the fossil record, to linger for varying but often very extended periods of time, and to disappear as suddenly as they arrived, to be replaced by other species which might or might not be closely related to them. For a long time--indeed, since Darwin himself--this failure of the fossils to accord with the expectation was explained away by the famous incompleteness of the record. But as the years passed and more and more fossils were found, the predictions of the Synthesis became increasingly out of sync with what was actually there. The time was evidently ripe for a reappraisal of the paleontologists' expectations from the theory--and thus of the theory itself. 4 |
He then goes on to explain the theory of punctuated equilibrium, which speculates that "speciation could occur fairly rapidly in small, isolated populations. Cut off from the larger gene pool by geographic barriers, a small amount of variation would be amplified by selection." 5
Freed from the annoying limitation of having to show any evidence of evolution from one form to another, all one needs to do is simply group the fossils by apparent similarity (using something called a cladogram) and draw a conclusion.
| Given the wealth of interpretations available, it's a tall order to encapsulate the state of play in paleoanthropology today. ... What I can most usefully do by way of summary is, I think, to follow my own advice and to review the evidence for the past of our species by advancing from the simple to the complex: from a cladogram, to a phylogenetic tree, and finally to a brief scenario of our evolution. 6 |
Then he goes on to tell his story. As Tattersall pointed out, how many of his colleagues or others buy his story depends principally on how convincing or forceful a storyteller he is--and on how willing his audience is to believe the kind of thing he is saying.
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Footnotes:
1
Tattersall (1995) The Fossil Trail pages 226-227
(Ev)
2 Ibid. page 165
3 Ibid. page 169
4 Ibid. pages 159 - 160
5
Milner, The Encyclopedia of Evolution (1993), page 375
(Ev+)
6
Tattersall (1995) The Fossil Trail page 229
(Ev)