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Catford could identify where people were from exclusively through their speech. His expertise – which included formal phonetics , the aerodynamic and physiological production of speech, phonetic peculiarities in speech, and an astounding ability to reproduce words, and even speeches, backwards – led him to be invited to the University of ...
Shifting balance theory aims to explain how this may be possible. The shifting balance theory is a theory of evolution proposed in 1932 by Sewall Wright, suggesting that adaptive evolution may proceed most quickly when a population divides into subpopulations with restricted gene flow.
Darwin's theory of evolution is based on key facts and the inferences drawn from them, which biologist Ernst Mayr summarised as follows: [6] Every species is fertile enough that if all offspring survived to reproduce, the population would grow (fact). Despite periodic fluctuations, populations remain roughly the same size (fact).
Neutral theory – Theory of evolution by changes at the molecular level; Shifting balance theory – One version of the theory of evolution; Price equation – Description of how a trait or gene changes in frequency over time; Coefficient of relationship – Mathematical guess about inbreeding; Fitness – Expected reproductive success
Evolution is the change in the heritable characteristics of biological populations over successive generations. [1] [2] It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, resulting in certain characteristics becoming more or less common within a population over successive generations. [3]
The word evolved in a modern sense was first used in 1826 in an anonymous paper published in Robert Jameson's journal and evolution was a relative late-comer which can be seen in Herbert Spencer's Social Statics of 1851, [a] and at least one earlier example, but was not in general use until about 1865–70.
In September 1838 he conceived his theory of natural selection as the cause of evolution, then as well as developing his career as a geologist and writer worked privately on finding evidence and answering possible objections. He wrote out his ideas in an 1842 "pencil sketch", then in an essay written in 1844.
Professor of biology Jerry Coyne sums up biological evolution succinctly: [3]. Life on Earth evolved gradually beginning with one primitive species – perhaps a self-replicating molecule – that lived more than 3.5 billion years ago; it then branched out over time, throwing off many new and diverse species; and the mechanism for most (but not all) of evolutionary change is natural selection.