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life towards ever-increasing mental powers and a "comfortable view of human inevitability and superiority." Gould argues that the definition of
Evolution to professional biologists is "adaptation to changing environments", not progress, and that the composition of life on the planet is rather a "copiously branching bush, continually pruned by the grim reaper of extinction, not a ladder of predictable progress." He discusses society's obsession with unsuccessful lineages as "textbook cases" of "evolution". To elaborate, we consistently seek out "a single line of advance from the true topology of copious branching. In this misguided effort, we are inevitably drawn to branches so near the brink of total annihilation that they retain only one surviving twig. We then view this twig as the acme of upward achievement, rather than the probable last grasp of a richer ancestry." Gould uses the
257:"Suppose that ten of a hundred designs will survive and diversify. If the ten survivors are predictable by superiority of anatomy (Interpretation 1), then they will win each time – and Burgess eliminations do not challenge our comforting view of life. But if the ten survivors are protégés of Lady Luck or fortunate beneficiaries of odd historical contingencies (Interpretation 2), then each replay of the tape will yield a different set of survivors and a radically different history. And if you recall from high-school algebra how to calculate permutations and combinations, you will realize that the total number of combinations for 10 items from a pool of 100 yields more than 17 trillion potential outcomes." -
391:= 1 problem," which refers to the limitation of basing all theories of life on a single example—life on Earth. This terrestrial bias could hinder the search for extraterrestrial life by assuming that alien life must conform to Earth-like biochemical frameworks. The authors propose a model that incorporates both deterministic and contingent processes, suggesting a spectrum of possibilities for how life could arise under different environmental conditions. This broader understanding of the origins of life, which includes both biomolecular and non-biomolecular pathways, has significant implications for astrobiology and the detection of extraterrestrial biosignatures.
360:"Even if fishes hone their adaptations to peaks of aquatic perfection, they will all die if the pond dries up. But grubby old buster the lungfish, former laughing stock of the piscine priesthood, may pull through - and not because a bunion on his great-grandfather's fin warned his ancestors about an impending comet. Buster and his kin may prevail because a feature evolved long ago for a different use has fortuitously permitted survival during a sudden and unpredictable change in the rules. And if we are Buster's legacy, and the result of a thousand other similarly happy accidents, how can we possibly view our mentality as inevitable, or even probable?" -
384:], proposing that non-biomolecular chemistry may have played a significant role in the emergence of life on Earth. The authors argue that prebiotic environments likely contained a diverse array of non-biomolecular compounds that could have contributed to the formation of life. This challenges the traditional view that life must arise solely from biomolecules, such as proteins and nucleic acids, and suggests that life's origins may be more complex and varied.
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cone can be visualized as an inverted
Christmas tree, with a narrow base and numerous branches proliferating outward into the present day. Gould presents an alternative hypothesis, however, which states that the history of life is better described as "decimation followed by diversification within a few remaining stocks", represented as a pyramid with a wide base of anatomical disparity that becomes increasingly constrained by
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The march of progress, Gould argues, has led to the popular interpretation that the evolution of increased mental powers, ultimately culminating in the development of man's complex brain, is the natural outcome of evolution. Thus, the term "Evolution" is often conflated with a linear progression of
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Gould's opinion, and the central argument of
Wonderful Life, is that "any replay of the tape of life would lead evolution down a pathway radically different from the road actually taken." Additionally, Gould argues, no outcome can be predicated from the start, but the resulting pattern that emerges
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is that if life initially proliferated into a greater variety of phyla than currently exist and were subsequently decimated by the stochastic grim reaper of extinction, what then can be said about the inevitability of human intelligence and superiority? Additionally, Gould asks what role historical
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Gould argues that the conventional view of evolution, as illustrated by the cone of increasing diversity, is flawed. It is typically assumed that early life is restricted in form, and from this restriction of form follows diversification into the variety of animal life that currently exists. This
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provides an apparent linear path from simplicity to complexity. The only reason the evolution of horses has become the canonical representation of progressive evolution is because their bush has been extremely unsuccessful. Instead, Gould argues, we should look to bats, antelopes, and rodents as
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play in the evolution of life on Earth. It is these central ideas which prompt Gould to propose a thought experiment called "replaying the tape of life." Its central essence is this: if we rewind the clock and replay the history of life on Earth numerous times, will we consistently see the same
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quickly proliferated into the diversity of forms seen today due to the availability of numerous ecological niches and was subsequently decimated by extinction level events throughout geological time. He also notes that the survival of groups following extinction events bears no relationship to
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of locating and extracting beetle larvae from wood, but do so by very different means (beak and elongated finger respectively) due to their respective evolutionary histories, as birds lack fingers and primates lack beaks. The unique flora and fauna of isolated locations on Earth, such as
77:, indicating that contingency and convergence may both play a role. Additionally, a trait may be convergent at a broader level of description while being divergent at a more detailed level, with an example being the differently structured wings of
93:. Knowing how common convergence is also requires more research into how often a trait failed to evolve under the same selective pressures, as well as into traits that evolved only once among all known organisms.
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of rewinding the "tape of life" to the distant past, and argued that even small changes to history would result in evolutionary outcomes very different from our world. Gould's thought experiment has inspired real
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These studies have found that repeatability in evolution is common, particularly in cases of similar founding populations, when defining repeatability broadly, and over the timescales observable in experiments.
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Ultimately, Gould explains, both the false iconography of the march of progress and our allegiance to the cone of increasing diversity have led us astray in our thinking about trends in evolutionary biology.
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champions of mammalian evolution as they present us with "thousands of twigs on a vigorous bush" and are the true embodiments of evolutionarily successful groups.
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process, and the outcomes of history can be sensitive to the details of the interactions and events that preceded them. Contingency was especially emphasized by
622:"Alternative Pathways in Astrobiology: Reviewing and Synthesizing Contingency and Non-Biomolecular Origins of Terrestrial and Extraterrestrial Life"
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Alternative
Pathways in Astrobiology: Reviewing and Synthesizing Contingency and Non-Biomolecular Origins of Terrestrial and Extraterrestrial Life
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outcome that is the reality we experience today? The outcome of this thought experiment has two possible interpretations, elaborated by Gould,
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has also been found to be unexpectedly widespread in nature, though it occurs more often among closely related taxa that share more genes and
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in
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level events as time moves forward. This is evidenced by the fact that the fossils excavated from the
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after replaying the tape of life would be just as interpretable and logical as our current situation.
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describes how the outcome of evolution may be affected by the history of a particular lineage.
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Some examples of contingency affecting evolutionary outcomes have been identified. In the
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in the lab and in the field, as well as study of living and extinct organisms as
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The quest for a universal theory of life: searching for life as we don't know it
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Blount, Zachary D.; Lenski, Richard E.; Losos, Jonathan B. (9 November 2018).
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traditional notions of
Darwinian success in normal times. For example,
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Contingency and
Convergence: Toward a Cosmic Biology of Body and Mind
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Chandru, Kuhan; Potiszil, Christian; Jia, Tony Z. (August 2024).
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Wonderful life : the
Burgess Shale and the nature of history
431:"Contingency and determinism in evolution: Replaying life's tape"
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Improbable
Destinies: Fate, Chance, and the Future of Evolution
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to illustrate this point, as the unbroken connection between
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extends Gould' contingency concept to the origins of life
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551:Gould, Stephen Jay. (17 September 1990).
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165:Relevant discussion may be found on the
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186:"Contingency" evolutionary biology
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480:"Evolutionary contingency"
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269:Evolutionary iconography
653:Cleland, Carol (2020).
448:10.1126/science.aam5979
326:The cone vs the pyramid
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301:evolution of the horse
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592:"Models of Evolution"
401:Speculative evolution
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753:Evolutionary biology
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171:improve this article
75:developmental biases
71:Convergent evolution
21:evolutionary biology
63:natural experiments
16:Evolutionary theory
441:(6415): eaam5979.
353:Cambrian explosion
54:thought experiment
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362:Stephen Jay Gould
333:natural selection
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293:march of progress
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285:iconography
128:during the
122:New Zealand
109:Woodpeckers
59:experiments
25:contingency
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606:2019-09-20
407:References
376:The paper
337:extinction
197:newspapers
83:pterosaurs
40:historical
573:916045701
457:0036-8075
289:evolution
227:June 2024
167:talk page
126:dinosaurs
36:Evolution
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395:See also
349:Cambrian
312:Eohippus
130:Mesozoic
113:aye-ayes
31:Overview
729:24 June
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509:25 June
435:Science
211:scholar
105:citrate
99:E. coli
79:insects
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626:Life
569:OCLC
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335:and
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