The Fundamental Theorem of Natural Selection
Suppose we have <i>n</i> different types of self-replicating entity, with the population <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>P</mi><mi>i</mi></msub>...
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oai:doaj.org-article:7f2826959cfe469e956c73ccfab82aa12021-11-25T17:29:39ZThe Fundamental Theorem of Natural Selection10.3390/e231114361099-4300https://doaj.org/article/7f2826959cfe469e956c73ccfab82aa12021-10-01T00:00:00Zhttps://www.mdpi.com/1099-4300/23/11/1436https://doaj.org/toc/1099-4300Suppose we have <i>n</i> different types of self-replicating entity, with the population <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>P</mi><mi>i</mi></msub></semantics></math></inline-formula> of the <i>i</i>th type changing at a rate equal to <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>P</mi><mi>i</mi></msub></semantics></math></inline-formula> times the fitness <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>f</mi><mi>i</mi></msub></semantics></math></inline-formula> of that type. Suppose the fitness <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>f</mi><mi>i</mi></msub></semantics></math></inline-formula> is any continuous function of all the populations <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>P</mi><mn>1</mn></msub><mo>,</mo><mo>…</mo><mo>,</mo><msub><mi>P</mi><mi>n</mi></msub></mrow></semantics></math></inline-formula>. Let <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>p</mi><mi>i</mi></msub></semantics></math></inline-formula> be the fraction of replicators that are of the <i>i</i>th type. Then <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>p</mi><mo>=</mo><mo>(</mo><msub><mi>p</mi><mn>1</mn></msub><mo>,</mo><mo>…</mo><mo>,</mo><msub><mi>p</mi><mi>n</mi></msub><mo>)</mo></mrow></semantics></math></inline-formula> is a time-dependent probability distribution, and we prove that its speed as measured by the Fisher information metric equals the variance in fitness. In rough terms, this says that the speed at which information is updated through natural selection equals the variance in fitness. This result can be seen as a modified version of Fisher’s fundamental theorem of natural selection. We compare it to Fisher’s original result as interpreted by Price, Ewens and Edwards.John C. BaezMDPI AGarticleFisher information metricnatural selectionpopulation biologyreplicator equationLotka–Volterra equationScienceQAstrophysicsQB460-466PhysicsQC1-999ENEntropy, Vol 23, Iss 1436, p 1436 (2021) |
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Fisher information metric natural selection population biology replicator equation Lotka–Volterra equation Science Q Astrophysics QB460-466 Physics QC1-999 |
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Fisher information metric natural selection population biology replicator equation Lotka–Volterra equation Science Q Astrophysics QB460-466 Physics QC1-999 John C. Baez The Fundamental Theorem of Natural Selection |
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Suppose we have <i>n</i> different types of self-replicating entity, with the population <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>P</mi><mi>i</mi></msub></semantics></math></inline-formula> of the <i>i</i>th type changing at a rate equal to <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>P</mi><mi>i</mi></msub></semantics></math></inline-formula> times the fitness <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>f</mi><mi>i</mi></msub></semantics></math></inline-formula> of that type. Suppose the fitness <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>f</mi><mi>i</mi></msub></semantics></math></inline-formula> is any continuous function of all the populations <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>P</mi><mn>1</mn></msub><mo>,</mo><mo>…</mo><mo>,</mo><msub><mi>P</mi><mi>n</mi></msub></mrow></semantics></math></inline-formula>. Let <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>p</mi><mi>i</mi></msub></semantics></math></inline-formula> be the fraction of replicators that are of the <i>i</i>th type. Then <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>p</mi><mo>=</mo><mo>(</mo><msub><mi>p</mi><mn>1</mn></msub><mo>,</mo><mo>…</mo><mo>,</mo><msub><mi>p</mi><mi>n</mi></msub><mo>)</mo></mrow></semantics></math></inline-formula> is a time-dependent probability distribution, and we prove that its speed as measured by the Fisher information metric equals the variance in fitness. In rough terms, this says that the speed at which information is updated through natural selection equals the variance in fitness. This result can be seen as a modified version of Fisher’s fundamental theorem of natural selection. We compare it to Fisher’s original result as interpreted by Price, Ewens and Edwards. |
format |
article |
author |
John C. Baez |
author_facet |
John C. Baez |
author_sort |
John C. Baez |
title |
The Fundamental Theorem of Natural Selection |
title_short |
The Fundamental Theorem of Natural Selection |
title_full |
The Fundamental Theorem of Natural Selection |
title_fullStr |
The Fundamental Theorem of Natural Selection |
title_full_unstemmed |
The Fundamental Theorem of Natural Selection |
title_sort |
fundamental theorem of natural selection |
publisher |
MDPI AG |
publishDate |
2021 |
url |
https://doaj.org/article/7f2826959cfe469e956c73ccfab82aa1 |
work_keys_str_mv |
AT johncbaez thefundamentaltheoremofnaturalselection AT johncbaez fundamentaltheoremofnaturalselection |
_version_ |
1718412294858211328 |