Tempo and Mode in Evolution Genetics and Paleontology 50 Years After Simpson (1995) / Chapter Skim
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Tempo and Mode in the Macroevolutionary Reconstruction of Darwinism
Tempo and Mode in the Macroevolutionary Reconstruction of Darwinism
Pages 125-144
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From page 125... ...
Stephen lay Gould is professor of geology in the Museum of Comparative Zoology at Harvard University, Cambridge, Massachusetts.
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From page 126... ...
But we can scarcely doubt that Lyell's major working postulate and philosophical premisehis uniformitarian vision became just as firmly embedded in Darwin's thought and scientific action. Lyell's uniformitarianism held that the full panoply of past events, even those of greatest extent and apparent effect, must be explained as extrapolations from causes now operating at their current observable rates and intensities.
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From page 127... ...
Consider two assessments of our absent contribution to evolutionary theory. Sadly, as Julian Huxley notes in beginning the first quote, paleontologists have often defended their own debasement an all too common phenomenon noted among slaves, hostages, and other oppressed people who adopt the assessments of their captors (psychologists even have a label for it, as the Patty Hearst syndrome)
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From page 128... ...
As a final illustration of the reductionistic biases that still beset this most comprehensive of fields, and of the usual tendency to ignore or devalue theory based on whole organisms or long times, the assigned reporter for Science magazine presented a remarkably skewed and parochial view of the conference that honored Simpson's Tempo and Mode at its half-century, and formed the basis for this published symposium (Cohen, 1994~. The meeting itself was broad and comprehensive, with talks spanning a full range of levels and durations, from molecules at moments to faunas over geological periods.
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From page 129... ...
S Haldane; and alignment of more traditional disciplines in natural history with this central theory in a series of books beginning with Dobzhansky in 1937, and continuing with Mayr in 1942 for systematics, Simpson in 1944 for paleontology, and Stebbins in 1950 for botany, among several others.
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From page 130... ...
He started from the principles of neontological Darwinism as he saw the theory emerging. He then asked if major features of the fossil record could be reconciled to this modern version of Darwinism, without postulating any special macroevolutionary theory.
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From page 131... ...
By using uniquely paleontological data about pattern to infer the unseeable processes of long temporal spans, paleontology may be an active purveyor of evolutionary theory. This strategy of using uniquely paleontological data about tempo to infer mode, and thus to develop theory directly from the domain of macroevolution, pervades Simpson's book and underlies all his examples.
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From page 132... ...
Simpson's general argument is both illuminating and correct: tempos are a unique paleontological domain; modes may be inferred from them, and status as a source for theory thus conferred upon paleontology. Why, then, did Simpson's work fail to establish such a role for the fossil record and not lead to an independent body of macroevolutionary theory as the deprecatory quotes cited in section one of this paper, all postdating Tempo and Mode, demonstrate?
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From page 133... ...
Thus, although Simpson did enunciate a methodology" modes from tempos—for discovering uniquely macroevolutionary theory, he applied the procedure to deny this possible outcome. In other words, he developed a method that might have yielded theory, and then claimed that none was to be found.
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From page 134... ...
385~. Quantum evolution was therefore transmogrified from a distinct mode to extrapolative accumulation of adaptive change at fastest rates: Quantum evolution, he now claimed, "is not a different sort of evolution from phyletic evolution, or even a distinctly different element of the total phylogenetic pattern.
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From page 135... ...
The existence of genuinely independent macroevolutionary theory does not imply that "the innumerable studies of micro-evolution would become relatively unimportant." These studies are vitally important both as controlling in their own domain, and powerfully contributory to macroevolution as well. Contributory, but neither exclusive nor
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From page 136... ...
But we must entertain the legitimacy of all logically coherent levels in order to find out. In seeking an independent body of macroevolutionary theory, not construed as contrary to microevolutionary knowledge, but viewed as truly complementary in bonding to produce a more satisfying total explanation, I would focus upon two themes that share the common feature of rejecting Darwin's uniformitarian extrapolationism, not his natural selection (or other major meanings of Darwinism)
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From page 137... ...
But mass extinctions are not coincident, and they are truly massive (up to 96% species death of marine invertebrates in a well-known estimate for the largest, late Permian great dying Raup, 1979~. They are, therefore, causal patterning agents separate from the daily Darwinism of normal times.
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From page 138... ...
(The first three properties are required to individuate any named item as a distinct entity rather than an arbitrary segment of a continuum; the last two are prerequisites for agents of Darwinian selection, defined as differential reproductive success.) Organisms are the quintessential biological objects endowed with these five properties, hence their role as canonical Darwinian individuals in the basic theory.
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From page 139... ...
Above this complex field, we encounter the two clear levels of truly macroevolutionary selection, largely based upon paleontological data, and capable of producing important phenomena of evolutionary pattern not fully rendered by causes at lower levels— species selection (Stanley, 1975; Jablonski, 1987; Vrba, 1989) for trends within clades and clade selection (Williams, 1992)
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From page 140... ...
10) of "two mutually exclusive domains of selection, one that deals with material entities and another that deals with information and might be termed the codical domain." But I do not think that the codical domain has meaning or existence as a locus for causal units of selection, for two reasons: (i)
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From page 141... ...
because the corresponding codex is impersistent. This linkage of selective agency to faithful replication has been so often repeated in the past decade that the statement has almost achieved status as dogma in evolutionary theory.
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From page 142... ...
However we ultimately define the levels in a genealogical hierarchy of effective selection upon each, and however we decide to codify the criteria for identifying selection at these levels, the hierarchical, multilevel theory of natural selection should put an end to an unhappy and unhelpful conflict rooted in the false mental tactic of dichotomization: the modes of macro- and microevolution as intrinsically opposed and in battle for a common turf. This model led the Synthesis to deny any theoretical status to macroevolution at all—thus preserving hegemony for a microevolutionary theory that could supposedly encompass all scales by smooth extrapolation.
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From page 143... ...
I describe the two major domains where a helpful macroevolutionary theory may be sought unsmooth causal boundaries between levels (as illustrated by punctuated equilibrium and mass extinction) and hierarchical expansion of the theory of natural selection to levels both below (gene and cell-line)
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From page 144... ...
(1986) Background and mass extinctions: The alternation of macroevolutionary regimes.
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