When1: 1977
When2: 2002
Who: Stephen Jay Gould [Gould, Stephen Jay]
What: biologist
Where: USA
works\ Ever Since Darwin [1977]; Ontogeny and Phylogeny [1977]; Spandrels of San Marco and the Panglossian Paradigm [1978: with Richard Lewontin]; Urchin in the Storm [1987]; Wonderful Life: The Burgess Shale and the Nature of History [1989]; Structure of Evolutionary Theory [2002]
Detail: Evolution repeats and modifies animal forms {bauplan, Gould}. Evolutionary changes can be in bursts {punctuated equilibrium, Gould}, even after 20,000 years with no change. Most traits are side effects. Timing changes during development cause evolutionary changes.
Organisms produce more offspring than survive to reproduce {superfecundity, Gould}. Darwin defended this idea against people that thought God is more benevolent. Offspring vary in traits. All accept this idea. Offspring pass their traits to offspring. All accept this idea. Therefore, offspring with traits more favorable for survival to reproductive age will produce more offspring with same traits {natural selection, Gould}.
Darwin's evolutionary theory has three main principles to explain natural-selection mechanisms. Natural selection applies to organisms, not classes, genuses, species, tissues, organs, or genes.
Darwin suggested that altruism in humans was trait outside this idea. Perhaps, altruism can explain hybridization and worker-insect sterility. Modern theory suggests genes, cell lines, organisms, demes, species, and clades evolve using selection and drift to change frequencies and parts. They can work synergistically, in opposition, or independently of nearby levels. Other possibilities can be entropy effect or complex system spontaneous ordering.
Natural selection removes unfit and designs fit, because variations from typical or average are small, random, and numerous and not always negative. Small and large variations accumulate over many generations. Variations can have different kinds and sizes {microevolution, Gould}. Modern theory adds structural, historic, and developmental factors. Natural selection gradually makes more-complex organisms and can make new higher-level organism species. However, modern theory adds mass extinctions, species sorting by punctuated equilibrium to alter clades, and other processes taking different times. Other possibilities can be inorganic and organic comparisons or new species-formation ideas.
Because organisms overproduce, nature has competing organisms and species, so new ones must replace or wedge aside existing ones, leading to better-adapted species. This requires that environment changes slowly compared to evolution and observed species changes.
Interactors, rather than replicators, can define selection. Emergent fitness, rather than emergent traits, causes higher-level selection. Species selection is main macroevolution method.
Evolutionary theory involves same framework as other scientific explanations. It involves causation vs. association. Event sequences relate or do not relate. Related events are consequences or not. Structures and functions exist. Logical conclusions come from premises. People can find causation direction. Determinism comes from fundamental-unit laws versus independent-level interactions. Changes are gradual, spurt, maintain stasis, are exponential, or rise and fall. It involves fundamental units, structure hierarchies, change rates, space scales, and time scales.
Darwin felt that nature had progressed, because organism and ecosystem design was good (Paley) and complexity was increasing. Besides, nature ordered itself in the most-efficient way by survival of fittest (Adam Smith).
Increased speciation leads to increased extinction.
Clade selection, species habitat tracking, and grouping in populations can cause stasis.
Organisms tend to evolve to larger size, from individual size advantages and structural factors {Cope's rule, Gould}.
Slow variation and slow environmental change helped ancient organisms alive today survive. Their clades had low speciation.
Clades have various speciation rates, which can change over time and mimic seemingly progressive linear species changes, as in horses and humans.
Humans are stable genetically if punctuated equilibrium is true.
Drift can go into available niches, but bacteria dominate life.
Geometric patterns and physical laws, such as surface-to-volume ratios and coordinate transformations, constrain structures and allow few alternatives. Historical development can impose homologies and regulations. Adaptation consequences {exaptation, Gould} can have later advantages.
Homology is internal structure similarity {homogeny, Gould}. Homology can result from fundamental internal structure {parallelism, Gould} or same external pressures {convergence, Gould}. Organisms can also perform similar functions with different structures {homoplasy, Gould}.
Darwin held that small structure shifts were adaptive, but cumulative-shift adaptations can be different {functional shift, Gould} {cooptation, Gould}. Initial stages have unpredictable uses, constrain future adaptation, and form sequence. Non-adaptive structures {spandrel, Gould} arise in association with adaptive structures, and these structures can later be for adaptation, at all hierarchy levels. Adaptive structures tend to limit further evolution through specialization, but adaptive structures make many more non-adaptive structures with which evolution can work.
Biological Sciences>Biology>History>Evolution
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Date Modified: 2022.0224