Pearl, Raymond, 1879-1940

Professor of biology at The Johns Hopkins University School of Hygiene and Public Health.

Raymond Pearl was a biologist and statistician. He spent most of his academic career (1918-1940) at the Johns Hopkins University, where he was Professor of Biometry and Vital Statistics and Director of the Institute of Biological Research. He was founder of the "Quarterly Review of Biology" and "Human Biology," he made significant contributions in the areas of biology, genetics, eugenics, and statistics.

An early and influential advocate for the importation of statistics into biological analysis, Raymond Pearl was a pioneer in American population biology and ecology. The son of Frank Pearl, a grocery clerk and shoe factory foreman, and Ida May McDuffee, Pearl attended Dartmouth College (A.B., 1899) and the University of Michigan (Ph.D., 1902). Like many students of his generation, Pearl traveled abroad after receiving his doctorate to strengthen his education, studying first at the University of Leipzig in 1905, and then under Karl Pearson at University College London (1905-1906). It was Pearson who quickened Pearl's interests in quantitative analysis and fostered his first efforts to apply statistics to population genetics. He married Maud Mary Dewitt, a fellow student at Michigan, and long his collaborator, in 1903.

Pearl's first academic appointments upon returning to the States were as an instructor of zoology at the University of Pennsylvania (1906-1907) and as chair of the Department of Biology at the Maine Agricultural Experiment Station (1907-1918). Befitting his position in Maine, Pearl was engaged primarily in applied research in the genetics of poultry and cattle. Through studies aimed at increasing the productivity of egg-laying in chickens, he turned from an analysis of the inheritance of individual traits to patterns of inheritance in populations. Recognizing, as Mendelian theory predicted, that individuals often did not express the same traits as their parents, Pearl began to study population-level characteristics such as birth rate, death rate, and population size, and to reconceptualize the genetic and environmental dynamics of evolutionary change. His work took him variously into a reanalysis of Malthus' predictions on population density and into direct conflict with the tendencies of much eugenic research to focus on individual traits and individual couples. By 1915, his reputation had grown widely enough in scientific circles to merit election to the American Philosophical Society and, in 1916, to the National Academy of Sciences.

Leaving Maine to become Professor of Biometry at Johns Hopkins in 1918, Pearl entered into the most productive period of his career. At Hopkins, where he served variously as Professor of Biology (1923-1940) and as statistician at the Johns Hopkins Hospital (1919-1935), Pearl turned a statistical eye toward the dynamics of human populations, producing remarkably accurate and durable estimates of changes in world population based upon the best-guess estimates for birth rate and longevity. More controversially, based upon U.S. Census data from 1920, he and Lowell J. Reed theorized that the logistic (sigmoidal) curve was in effect a law of nature describing population growth: after a slow initial period of expansion, populations enter a phase of exponential growth until the they reach the carrying capacity of the environment and level off. Although recognized as a useful heuristic for exploring population dynamics, Pearl's aggressive promotion of the logistic curve and his truculence in its defence alienated many of his colleagues. In other research, Pearl experimented with the factors influencing population dynamics in Drosophila melanogaster, turned to estimates of life expectancy based upon occupation and personal habits, and entered into various statistical aspects of reproductive behavior. An inveterate opponent of most eugenic policies, and critic of eugenic research, he was nevertheless a strong and vocal supporter of birth control and population planning.

Using funds provided by the Rockefeller Foundation, Pearl established the Institute for Biological Research at Johns Hopkins in 1925, heading it throughout its five year existence. He was also active in numerous professional organizations, serving as president of the International Union for Scientific Investigation of Population Problems (1928-1931), the American Association of Physical Anthropologists (1934-1936), and the American Statistical Association (1939),and helping to found and edit the Quarterly Review of Biology in 1926 and Human Biology in 1929. An agile and prolific writer, Pearl wrote 17 books and nearly 700 articles during his career on a extraordinary range of subjects.