Pearson, Karl [formerly Carl]

(1857-1936), statistician and eugenicist

by Joanne Woiak

© Oxford University Press 2004 All rights reserved

Pearson, Karl [formerly Carl] (1857-1936), statistician and eugenicist, was born at 14 Albion Road, Holloway Road, Islington, London, on 27 March 1857, the second of three children of William Pearson (d. 1907), a barrister of the Inner Temple, and his wife, Fanny Smith (d. 1905), both of Yorkshire descent. He had an older brother, Arthur, and a younger sister, Amy, was born in 1859.

From 1863 to 1866 Karl and Arthur both boarded at William Penn's small school in Harrow. Then, for a short time in 1866, they received tuition from Penn at their family home, which allowed them to be closer to a mother who provided the emotional sustenance denied them by their stern and hard-working father. In the autumn of 1866 Karl was sent to University College School, London. He withdrew in 1873 owing to poor health and then went up to Cambridge to study with several private tutors. In April 1875 he obtained a scholarship at King's College, Cambridge, placing second on the list.

While at King's, Pearson gained notoriety when he rebelled against the required divinity lectures and chapel attendance, a campaign that resulted in the abolition of this system in March 1878. Although Pearson's rebellion was directed more against the requirements than against religion itself (after being released from compulsory chapel he shocked the tutors and deans by continuing to attend whenever the spirit moved him), it was nevertheless indicative of his early loss of Christian faith. He considered himself fortunate to have been raised by Quaker parents who did not encourage dogmatic belief in the biblical story of creation. By the time he was in his early twenties he had absorbed Darwinism and taken a special interest in Spinozism as an intellectual religion, thereafter identifying himself as a freethinker and an agnostic.

Pearson graduated BA in 1879 as third wrangler in the prestigious mathematical tripos. He was next awarded a King's College fellowship that allowed him financial independence for several years and an opportunity to travel to Heidelberg and Berlin, where he spent about eighteen months studying mathematics, physics, and philosophy. His first two publications (both anonymous) arose from his wide reading in philosophy, religious thought, and German history: The New Werther (1880) was a work of fiction written in the form of letters from a young man wandering in Germany seeking a creed of life, and The Trinity: a Nineteenth Century Passion Play (1882) attacked orthodox Christianity from the point of view of modern science and culture. Some of his essays and lectures dating from this period and covering a similarly broad range of topics were published in his Ethic of Freethought (1888).

Pearson's father had always intended that his sons follow him into the law, and so upon his return to London in November 1880 Karl entered Lincoln's Inn to prepare for a legal career and ensure himself a future livelihood. He was called to the bar at the end of 1881 but practised only a short time, apparently having been persuaded by the civil engineer Sir Alexander Kennedy to abandon law and return to mathematics, the subject at which he had excelled in his undergraduate studies.

Mathematics, mechanics, and The Grammar of Science
Pearson next worked as a substitute lecturer in mathematics at both King's and University colleges in London, and published work on elasticity and the motions of bodies in fluid media. In June 1884 he received his first academic appointment as Goldsmid professor of applied mathematics and mechanics at University College. He was reported to have been an effective and charismatic teacher, devoting considerable time and energy to these duties while also producing an impressive output of original work in applied mathematics, including the laborious task of completing Isaac Todhunter's History of the Theory of Elasticity (2 vols., 1886-93).

Pearson's major accomplishment of this early period was his Grammar of Science (1892), later widely recognized as a significant contribution to positivist and phenomenalist philosophy of science. Pearson held that all knowledge was based on sense perceptions and that the task of science was to summarize the routines of experience by means of laws expressed in mathematical form. Theoretical terms such as 'atom' or 'gene' were allowable only when they served as instruments for economically describing phenomena, not when they were interpreted as referring to invisible entities. Thus for example he criticized certain evolutionists for seeking the hidden causes of biological variability rather than just trying to provide a quantitative description: 'the why of it is as much a mystery as the why of the law of gravitation' (Pearson, The Grammar of Science, 2nd edn, 1900, 451).

Pearson's phenomenalist stance was also articulated in a series of lectures he gave as holder of the Gresham College chair of geometry from 1891 to 1893. His Gresham lectures 'The geometry of statistics' and 'The laws of chance', in which audiences of as many as 300 students witnessed him use dice, roulette results, and 10,000 pennies scattered on the floor to demonstrate the laws of probability, marked a significant turning point in his career: they represented his earliest forays into statistical theory, the branch of mathematics in which he would soon make his scientific reputation. Pearson was responsible for almost single-handedly establishing the modern discipline of mathematical statistics, including the invention of a number of essential statistical techniques, most notably the chi-square test for goodness of fit and the product moment method of calculating the correlation coefficient.

Pearson's interest in statistics was stimulated by Sir Francis Galton (1822-1911), the father of eugenics, and by W. F. R. Weldon, the zoologist who subsequently co-founded with Pearson the discipline called biometry, or the application of mathematical methods to the biological sciences. In the early 1890s Weldon sought out Pearson's assistance with the mathematical analysis of morphological variations in crab populations. His research involved determining whether a double humped frequency distribution for a given trait could be broken down into two normal curves representing a dimorphic population undergoing speciation. In the course of addressing such problems in evolutionary theory Pearson introduced powerful new statistical tools, especially his method of moments and system of frequency curves. Between 1894 and 1901 he communicated this work on curve fitting in a series of important papers in the Philosophical Transactions of the Royal Society. By 1906 he had already published over a hundred articles on statistical theory and applications.

Correlation theory and interest in eugenics
Correlation theory constituted Pearson's other key line of research in mathematical statistics. The history of correlation began with Galton's work on inheritance, anthropometrics, and criminal identification carried out between 1876 and 1889. Thereafter the methods he invented for measuring variation and correlation were applied and extended mainly by his disciples Weldon and Pearson. Pearson recounted that Galton's Natural Inheritance (1889) had opened his eyes to the potential uses of statistical analysis for obtaining valid knowledge about living forms and human behaviour. After his initial success with speciation, Pearson went on to develop further statistical innovations particularly useful for the study of heredity and eugenics. For instance, in his very first correlation paper of 1896 he illustrated the practical value of these new tools by calculating regressions of offspring under selection pressures and by confirming the high degree of association between excessive fertility and undesirable traits. Later he utilized correlation coefficients and family pedigrees in his attempts to demonstrate that heredity was more important than environment in determining numerous human attributes and pathologies. Most of this material appeared in the multi-volume Treasury of Human Inheritance (1909-33). This research seemed to confirm the eugenic assumption that social reforms were powerless to remedy the crisis of racial degeneration: if health and ability were principally inborn traits, then only programmes for selective breeding could improve the biological fitness of the population.

Several of Pearson's essays dating from the 1880s and 1890s, published in his Chances of Death, and other Studies in Evolution (2 vols., 1897), show that he had already begun to explore scientific ideas that would become central components of his eugenic creed, such as Darwinism, the inheritance of physical and mental characteristics, and the differential fertility of fit and unfit stocks. His conversion to socialism during his year in Germany also influenced his thinking on the questions of national efficiency and racial health. Upon returning to London in 1881 he became associated with radical clubs where he lectured on Marx and Lassalle and wrote hymns for the socialist songbook. However, Pearson's version of socialism was reformist rather than revolutionary, defined in terms of ensuring a stable society and a strong state. His politics most closely resembled Fabian socialism, with its emphasis on replacing laissez-faire capitalism with state planning and technocratic management. He theorized that the way to regenerate the vitality of the British populace was by minimizing the struggle for existence between individuals through social welfare legislation and eugenics, while keeping up the intense competition between nations in the military and commercial realms.

Pearson's eugenics must also be considered in relation to his keen interest in the 'woman question'. In 1885 he had founded the Men and Women's Club as a forum for dispassionate discussion of questions pertaining to sexual relations. While the female members of the club were most concerned to voice their anxieties about such concrete problems as prostitution, coercive sex, and birth control, Pearson read papers on sexual passion and the eugenic significance of feminism. He considered himself a supporter of equal rights and opportunities for women (later in his capacity as a laboratory director he hired many female assistants), yet he also expressed a willingness to subordinate these ideals to the greater good of the race. Eugenic feminists such as Pearson still expected liberated women to sacrifice their individual development in order to fulfil their duties as race mothers. The Men and Women's Club further served as an opportunity for the rather shy Pearson to realize his courtship ambitions. After rebuffing the sexual overtures of the South African feminist Olive Schreiner, on 30 June 1890 he married another fellow club member, Maria Sharpe (1853-1928). They had one son and two daughters. After Maria's death Pearson married, on 22 March 1929, one of his long-time biometrical co-workers, Margaret Victoria Child.

By 1901 Pearson was devoting his full time to research and teaching in the new mathematical field of statistics, work for which he was awarded a grant from the Worshipful Company of Drapers that enabled him to establish a biometric laboratory at University College, London. He closely supervised all the projects undertaken by his staff and students, which ranged from further advances in statistical methodology to the analysis of data on heredity and physical anthropology. He also published on some non-biological topics such as astronomy and dam construction, thereby demonstrating the wide applicability of his new analytical techniques. He and Weldon founded the journal Biometrika in 1901 as a publication outlet for their original work in both mathematics and biology.

Eugenics came to occupy an especially prominent place on Pearson's research agenda after the death of his close friend and collaborator Weldon in 1906. Pearson took over the directorship of the Eugenics Record Office at the behest of its benefactor Francis Galton in 1907, changing the name of this institution to the Galton Laboratory for National Eugenics. In this role he gave public lectures expounding the new science and with the help of a dedicated staff carried out painstaking statistical studies of various social ills. In 1911 he was appointed the first Galton professor of eugenics at University College. The eugenics and biometric laboratories were incorporated into a single department of applied statistics, which survived until Pearson's retirement in 1933 when separate departments of eugenics (later human genetics) and statistics were set up against his express wishes that the connection between these two sciences be maintained. R. A. Fisher subsequently held the chair in eugenics while Pearson's son Egon Pearson became the new professor of statistics.

Over the course of three decades Karl Pearson published some fifty papers on eugenics, constituting almost 10 per cent of his remarkably prolific scientific output. His publications and joint laboratories laid the intellectual and institutional foundations of modern statistics. From the 1890s until the 1920s the biometrical school at University College represented the only place in Britain that offered advanced training in statistical methods. It attracted postgraduates and visitors from many disciplines and from around the world. The first generation of professional medical and biostatisticians were all Pearson's pupils, including Major Greenwood in Britain and Raymond Pearl in the United States. Statistics soon achieved recognition as a scientific speciality in its own right, with statistical workers in demand in academia, government, and industry. But Pearson's second goal, of establishing a eugenics laboratory in every British university, was never realized, since public interest in eugenics waned after the First World War and most of the biometricians he trained did not go on to help him spread the gospel of eugenics along with the new techniques of correlation.

Pearson disparaged old-school statisticians such as the members of the Royal Statistical Society (an organization he himself never joined) for employing a crude style of vital statistics that consisted simply of comparing percentages in order to make inferences about the causes of diseases and social problems. He insisted that only his biometricians were competent to analyse data collected in the laboratory, clinic, and social survey on such critical issues as alcoholism, tuberculosis, and infant mortality. His eugenics writings were marked by an extreme scepticism towards the investigations carried out by physicians and experimentalists, an attitude that on numerous occasions incited controversies with these reigning experts. The biometrical school is best known in the history of biology for its opposition to the Mendelian theory of heredity, which seemed to be inconsistent with Pearson's phenomenalism and evolutionary gradualism. Pearson similarly engaged in a fierce dispute with temperance advocates and fellow eugenicists over the question of whether parental alcoholism produced degeneracy in offspring.

In an autobiographical sketch written in 1934 Pearson accounted for his scientific achievements and success in founding a new academic discipline in terms of two purportedly inherited qualities: 'a capacity for hard work and a capacity for roving into other people's preserves' (quoted in Pearson, Karl Pearson, 2). He was an energetic teacher and researcher, as well as an inspirational if domineering leader of his research institute. Although always extremely generous with his co-workers, Pearson was also reportedly prone to angry outbursts. He engaged in intellectual disputes that often descended into personal bitterness, even with some of his former pupils and friends. He tended to be impatient and even insulting towards outsiders who were unable or unwilling to see his point of view, especially those who objected to his uncompromising hereditarianism. Pearson was sometimes labelled a proponent of the 'better-dead school' of eugenics, owing to his apparent lack of sympathy for the sick and the poor and his endorsement of brutal competition between nations or racial groups as the means of achieving evolutionary progress. He championed further statistical studies as the prerequisite for an effective programme of race regeneration, yet his own proposals for positive and negative eugenics were based more on social class prejudices than on sound scientific deductions.

For his fundamental contributions to statistics and evolutionary theory, Pearson was elected FRS in 1896 and awarded the society's Darwin medal in 1898. In 1903 he was awarded the Huxley medal of the Royal Anthropological Institute and in 1932 the Rudolf Virchow medal by the Anthropological Society of Berlin. He accepted the honorary degree of LLD from the University of St Andrews and of DSc from the University of London, and he was elected an honorary fellow of King's College, Cambridge, of the Royal Society of Edinburgh, and of University College, London. Pearson died suddenly while on holiday at his cottage, the Old School House, Coldharbour, Dorking, Surrey, on 27 April 1936. He was survived by his second wife.


E. S. Pearson, Karl Pearson: an appreciation of some aspects of his life and work (1938)
G. U. Yule, Obits. FRS, 2 (1936-8), 73-104
D. MacKenzie, Statistics in Britain, 1865-1930: the social construction of scientific knowledge (1981)
T. M. Porter, The rise of statistical thinking, 1820-1900 (1986)
B. Norton, 'Karl Pearson and statistics: the social origin of scientific innovation', Social Studies of Science, 8 (1978), 3-34
D. J. Kevles, In the name of eugenics (1985), 20-40
B. Norton, 'Biology and philosophy: the methodological foundations of biometry', Journal of the History of Biology, 8 (1975), 85-93
J. R. Walkowitz, City of dreadful delight: narratives of sexual danger in late-Victorian London (1992), 135-69
M. E. Magnello, 'Karl Pearson's Gresham lectures: W. F. R. Weldon, speciation and the origins of Pearsonian statistics', British Journal for the History of Science, 29 (1996), 43-63
C. Eisenhart, 'Pearson, Karl', DSB, 10.447-73
M. Merrington and others, A list of the papers and correspondence of Karl Pearson (1857-1936) held in the Manuscripts Room, University College London Library (1983)
K. Pearson, The life, letters and labours of Francis Galton, 3 vols. in 4 (1914-30)
M. E. Magnello, 'Karl Pearson', The encyclopaedia of biostatistics, ed. P. Armitage and J. Cotton (1998), 3308-15
CGPLA Eng. & Wales (1936)

RS, letters
UCL, corresp. and papers
Wellcome L., corresp. with Eugenics Society |  King's AC Cam., letters to Henry Bradshaw
King's AC Cam., letters to Oscar Browning
Royal Anthropological Institute, London, corresp. with M. L. Tildesley
UCL, corresp. with Sir Francis Galton

Elliott & Fry, two photographs, 1890, NPG
photograph, c.1897, NPG
two photogravures, 1910, NPG [see illus.]
F. A. de Biden Footner, pencil drawing, 1924, UCL
photograph, 1928, NPG
Crellin, carte photograph (as a child), NPG
H. R. Hope-Pinker, bust, UCL
photographs, repro. in Pearson, Karl Pearson

Wealth at death  
£37,576 5s. 7d.: resworn probate, 2 July 1936, CGPLA Eng. & Wales

Oxford University Press 2004 All rights reserved


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