Editing Karl Pearson (section)

== Contributions to biometrics ==
Karl Pearson was important in the founding of the school of biometrics, which was one of several competing theories to describe evolution and population inheritance at the turn of the 20th century. His series of eighteen papers, "Mathematical Contributions to the Theory of Evolution" established him as the founder of the biometrical school for inheritance. In fact, Pearson devoted much time during 1893 to 1904 to developing statistical techniques for biometry.<ref>{{Cite journal|last=Farrall|first=Lyndsay A.|date=August 1975|title=Controversy and Conflict in Science: A Case Study The English Biometric School and Mendel's Laws|journal=Social Studies of Science|volume=5|issue=3|pages=269–301|doi=10.1177/030631277500500302|pmid=11610080|s2cid=8488406}}</ref> These techniques, which are widely used today for statistical analysis, include the [[chi-squared test]], [[standard deviation]], and [[Correlation and dependence|correlation]] and [[Regression analysis|regression]] coefficients. Pearson's Law of Ancestral Heredity stated that germ plasm consisted of heritable elements inherited from the parents as well as from more distant ancestors, the proportion of which varied for different traits.<ref>{{Cite journal|last=Pearson|first=Karl|date=1897|title=Mathematical Contributions to the Theory of Evolution. On the Law of Ancestral Heredity|jstor=115747|journal=Proceedings of the Royal Society of London|volume=62|issue=379–387|pages=386–412|bibcode=1897RSPS...62..386P|doi=10.1098/rspl.1897.0128|url=https://zenodo.org/record/1432096|doi-access=free}}</ref> Karl Pearson was a follower of [[Francis Galton|Galton]], and although the two differed in some respects, Pearson used a substantial amount of Francis Galton's statistical concepts in his formulation of the biometrical school for inheritance, such as the law of regression. The biometric school, unlike the [[Mendelians]], focused not on providing a mechanism for inheritance, but rather on providing a mathematical description for inheritance that was not causal in nature. While Galton proposed a discontinuous theory of evolution, in which species would have to change via large jumps rather than small changes that built up over time, Pearson pointed out flaws in Galton's argument and actually used Galton's ideas to further a continuous theory of evolution, whereas the Mendelians favored a discontinuous theory of evolution. While Galton focused primarily on the application of statistical methods to the study of heredity, Pearson and his colleague Weldon expanded statistical reasoning to the fields of inheritance, variation, correlation, and natural and sexual selection.<ref name=":02">{{Cite journal|last=Pence|first=Charles H.|date=2015|title=The early history of chance in evolution|journal=Studies in History and Philosophy of Science|volume=50|pages=48–58|doi=10.1016/j.shpsa.2014.09.006|pmid=26466463|bibcode=2015SHPSA..50...48P|citeseerx=10.1.1.682.4758|s2cid=29105382 }}</ref>

For Pearson, the theory of evolution was not intended to identify a biological mechanism that explained patterns of inheritance, whereas [[Mendelian inheritance|Mendelian's theory]] postulated the [[gene]] as the mechanism for inheritance. Pearson criticized [[William Bateson|Bateson]] and other biologists for their failure to adopt biometrical techniques in their study of evolution.<ref>{{Cite journal|last=Morrison|first=Margaret|date=1 March 2002|title=Modelling Populations: Pearson and Fisher on Mendelism and Biometry|journal=The British Journal for the Philosophy of Science|volume=53|issue=1 |pages=39–68|doi=10.1093/bjps/53.1.39|s2cid=145804261}}</ref> Pearson criticized biologists who did not focus on the statistical validity of their theories, stating that "before we can accept [any cause of a progressive change] as a factor we must have not only shown its plausibility but if possible have demonstrated its quantitative ability"<ref name=":12">{{Cite book|url=https://catalog.hathitrust.org/Record/100579982|title=The grammar of science|last=Pearson|first=Karl|date=1892|publisher=Walter Scott; Charles Scribner's Sons|series=The contemporary science series|location=London : New York}}</ref> Biologists had succumb to "almost metaphysical speculation as to the causes of heredity," which had replaced the process of experimental data collection that actually might allow scientists to narrow down potential theories.<ref>{{Cite journal|last=Pearson|first=Karl|date=1896-01-01|title=Mathematical Contributions to the Theory of Evolution. III. Regression, Heredity, and Panmixia|journal=Philosophical Transactions of the Royal Society of London A: Mathematical, Physical and Engineering Sciences|language=en|volume=187|pages=253–318|doi=10.1098/rsta.1896.0007|issn=1364-503X|bibcode=1896RSPTA.187..253P|doi-access=free}}</ref>

For Pearson, laws of nature were useful for making accurate predictions and for concisely describing trends in observed data.<ref name=":02" /> Causation was the experience "that a certain sequence has occurred and recurred in the past".<ref name=":12" /> Thus, identifying a particular mechanism of genetics was not a worthy pursuit of biologists, who should instead focus on mathematical descriptions of empirical data. This, in part led to the fierce debate between the biometricians and the Mendelians, including [[William Bateson|Bateson]]. After Bateson rejected one of Pearson's manuscripts that described a new theory for the variability of an offspring, or homotyposis, Pearson and Weldon established [[Biometrika]] in 1902.<ref>{{Cite journal|last=Gillham|first=Nicholas|date=9 August 2013|title=The Battle Between the Biometricians and the Mendelians: How Sir Francis Galton Caused his Disciples to Reach Conflicting Conclusions About the Hereditary Mechanism|journal=Science & Education|volume=24|issue=1–2|pages=61–75|doi=10.1007/s11191-013-9642-1|bibcode=2015Sc&Ed..24...61G|s2cid=144727928}}</ref> Although the biometric approach to inheritance eventually lost to the Mendelian approach, the techniques Pearson and the biometricians at the time developed are vital to studies of biology and evolution today.