See, also, Troy Britain's "Feedback" article at Talk. June Feedback - J. We must distinguish between the fact of evolution -- defined as change in organisms over time -- and the explanation of this change. Darwin's contribution, through his theory of natural selection, was to suggest how the evolutionary change took place. The evidence we find in the geologic record is not nearly as compatible with darwinian natural selection as we would like it to be.
Note that Raup believes that evolution has occurred; he calls evolution a "fact". And on page 25 he writes: What appeared to be a nice progression when relatively few data were available now appears to be much more complex and much less gradualistic. So Darwin's problem has not been alleviated in the last years and we still have a record which does show change but one which can hardly be look upon as the most reasonable consequence of natural selection. So natural selection as a process is okay.
We are also pretty sure that it goes on in nature although good examples are surprisingly rare. It should be obvious by now that what Raup is arguing against is not evolution, but gradual evolution in all cases.
This record has never revealed traces of Darwin's hypothetical intermediate variants instead species appear and disappear abruptly, and this anomaly has fueled the creationist argument that each species was created by God. This quote is from a Canadian newsmagazine, and would be relatively obscure outside of Canada. The quote has clipped off part of the last sentence, and some of the punctuation has changed: A major problem in proving the theory has been the "fossil record," the imprints of vanished species preserved in the Earth's geological formations.
This record has never revealed traces of Darwin's hypothetical intermediate variants - instead, species appear and disappear abruptly, and this anomaly has fueled the creationist argument that each species was created by God as described in the Bible. Once again, this seems to be a glossing over of the controversy surrounding Punctuated Equilibrium. Given that many in the news media seem to have a superficial understanding of science, I'm not inclined to take the technical aspects of a news article about the evolution-creation controversy seriously, especially when I see a gem like this: Essentially, Darwin stated that a species evolved by the random mutation of genes, which then produced variants of the original species.
The claim that Darwin knew about genes and mutation is news to me, as I'm sure it is to a lot of people. But Czarnecki does raise an interesting point. Discussing how some people view the difference between fact and theory, he writes: Such a pedagogical approach, though initiated with the best of intentions, strips the corpus of scientific knowledge down to certain facts that can be perceived by the five senses with the aid of technology; everything else is factually suspect because it cannot be directly "observed" - so much for paleontology fossil study and all of nuclear physics.
And a few sentences later: Past events cannot be observed, records of them are just fallible memories, words - just like the Bible, in fact. On this view, there is little evidence of modification within species, or of forms intermediate between species because neither generally occurred.
A species forms and evolves almost instantaneously on the geological timescale and then remains virtually unchanged until it disappears, yielding its habitat to a new species. I found this particular one in the 19 November issue volume , number It is a review by Peter J.
Smith of Niles Eldredge's "Life Pulse. Perhaps I should also note this additional sentence from the review: Both he and Gould have noted, however, that they are not completely lacking and that examples of transitionals between higher taxonomic groups are even more common. A theory is only as good as its predictions, and conventional neo-Darwinism, which claims to be a comprehensive explanation of evolutionary process, has failed to predict the widespread long-term morphological stasis now recognized as one of the most striking aspects of the fossil record.
But punctuated equilibrium is compatible with much current neo-Darwinian thought. The principal argument in my paper is that when speciation events occur in the Turkana Basin mollusc sequence, they are invariably accompanied by major developmental instability So we can see that Williamson isn't criticizing evolution, or all of neo-Darwinism, but one aspect of it, namely gradualism.
Individual organisms and, in the later two cases, entire species tend to survive by moving around, sending out propagules to rebuild ecosystems, whether locally degraded Cercopia on El Yunque or regionally revamped as when glaciers slowly move south from the arctic. But evolution is classically about change.
So far, local and regional patterns of ecological resiliency imply stability of individual species lineages, not evolutionary change. Where and how does real evolution come into the picture? Prior to Hugo's hit in , the endemic Puerto Rican parrot had been reduced to fewer than known individuals living in the Loquillo Mountains, of which El Yunque is one. Agriculture and urbanization had already transformed so much of this bird species' habitat that it was on the verge of extinction.
Hugo took about 50 percent of the remaining birds. Though the population has since recovered to approximately pre-Hugo proportions, and is now being augmented by a captive breeding program, Hugo might very well have done away with these beautiful animals entirely. Indeed, it can drive many different species extinct all at the same time.
And that's exactly what we paleontologists see in the fossil record as the dominant pattern, not only of extinction, but of evolution as well.
Virtually all the component species of regional ecosystems are evolutionarily stable, often for millions of years. Of course, that's only half the pattern. Periodically, the majority of those species disappear, to be replaced, in due course, by others. One way of looking at this pattern is to see it as the ecological generalization of stasis and change that underlies the notion of punctuated equilibria.
It is a simple ineluctable truth that virtually all members of a biota remain basically stable, with minor fluctuations, throughout their durations. Remember, by "biota" we mean the commonly preserved plants and animals of a particular geological interval, which occupy regions often as large as Roger Tory Patterson's "eastern" region of North American birds.
And when these systems change -- when the older species disappear, and new ones take their place -- the change happens relatively abruptly and in lockstep fashion. It affects most of the species in a region more or less at the same time. Evolution goes hand in hand with the degradation and rebuilding of ecosystems, and the origin of new species depends in large measure on the extinction of older species.
Freeman and company, New York. Simpson have held that most evolutionary transitions occur within established lineages by phyletic gradualism guided by natural selection. But fossil species remain unchanged thoughout most of their history and the record fails to contain a single example of a significant transition.
Similarly, it is difficult to account for the greatly accelerated pace of evolution during periods of adaptive radiation.
An alternative model of evolution, that of punctuated equilibria, introduced by Niles Eldredge and Stephen Jay Gould in the early s, more fully accounts for these same observations. In case you haven't already guessed, that's what this quote is.
The author is reminding that gradualist hypotheses for the mechanism of evolution have a hard time explaining the fossil record, while punctuated equilibrium hypotheses on evolutionary mechanisms make much more sense in light of the same fossil record.
This article is actually not a scientific paper in itself but rather a review by Woodroff of Steven Stanley's "Macroevolution. Pattern and Process" Freeman S.
The first sentences of this article reads thus brackets mine: One of the major debates in biology concerns the role of micro-evolutionary forces natural selection, genetic drift and mutation at the trans-species level. Are the major changes in the history of life attributable to speciation or to the gradual transformation of lineages within established species by microevolutionary forces?
Woodroff goes on to describe Stanley's contributions to biology, and the wealth of analyses Stanley includes within the volume, including "well-illustrated data on rates of speciation, extinction, and the diversification of higher taxonomic categories.
The problem of the varying speed by which species diversification appears in the fossil record is addressed as: Darwin and most subsequent authors including G. But fossil species remain unchanged throughout most of their history and the record fails to contain a single example of a significant transition. An alternative model of evolution, introduced by Niles Eldredge and Stephan Jay Gould in the early 's, more fully accounts for these same observations.
According to this major conceptual breakthrough, rapid evolution is typically associated with speciation events that occur cryptically in small isolated populations, often at the edge of a species's geographic range.
Clearly the authors intended the reader to note the weakness in gradualism, not to doubt the fact that the fossil record supports evolutionary theory, as the little quote nugget at the top of this record seems to imply.
An Agenda for Paleobiology," Paleobiology , , p. It is implying sloppy scientific methods when the true quote has only a superficial resemblance to the word and none to the meaning.
It is a complete fabrication of the original sentence by the source which was: But as I am obliged to give the full context of the "quote nugget", knowing it's my scholarly duty, let's go to it We must first start with the abstract. Gould presents the basics of his argument within the article's abstract, which is very important to read in this context. Here is quoted the entire abstract on page 2: Conventional evolutionary theory denies this structuring and attempts to render the larger scales at simple extrapolation from or reduction to the familiar and immediate -- the struggle among organisms at ecological moments conventional individuals at the first tier.
I propose that we consider distinct processes at three separable tiers of time: I suggest a resolution of the paradox: In particular, punctuated equilibrium at the second tier produces trends for suites of reasons unrelated to the adaptive benefits of organisms conventional progress.
Mass extinction at the third tier, a recurring process now recognized as a more frequent, more rapid, more intense and more different than we had imagined, works by different rules and may undo whatever the lower tiers had accumulated. An Agenda for Paleobiology," Paleobiology 11 1 , pp Now, to set the context of the "quote nugget" cited at the top of this section, it is in the light of the discussion on the "third tier". Note how Gould is criticizing other aspects of his field in its conclusions and methods, a habit that is typical of most critically-thinking scientists and is a necessary and prevalent method of discourse in science.
Establishment of the Independence of the Third Tier. As ideas whose time may have come, mass extinction shares an interesting property with punctuated equilibrium. Neither represents a new discovery; both involve the reluctant acceptance of an acknowledged literal pattern that deep biases of Western thought had led us to mitigate or deny.
Just as we have long known about stasis and abrupt appearance, but have chose to fob it off upon an imperfect fossil record, so too have we long recognized the rapid, if not sudden, turnover of faunas in episodes of mass extinction. We have based our geological alphabet, the time scale, upon these faunal replacements.
Yet we have chosen to blunt or mitigate the rapidity and extent of extinctions with two habits of argument rooted in uniformitarian commitments. First, we have deemphasized some extinctions by drawing dubious phyletic connections across the boundaries. Second, and more important, we have tried to distribute these events more evenly in time by seeking evidence for slow declines before boundaries and reduced peaks of extinction at the terminations themselves.
In short, we have tried to place mass extinctions into continuity with the rest of life's history by viewing them as only quantitatively different -- more and quicker of the same -- rather than qualitatively distinct in both rate and effect. I would also like to add that in the previous section within this same paper, on the subject of the "Second Tier", Gould was making the case for the mechanism of punctuated equilibrium, where he showed that gradualism does not explain the stasis and abrupt appearance in the fossil record, which is in context with the work itself.