The Scientists Collection is comprised of individual letters and small groups of correspondence from American, British, French, and German scientists during the past three centuries. Although the content is highly varied, there is significant strength in astronomy, natural history, conchology, and geology. Among the scientists better represented in the collection are the astronomers William Radcliffe Birt, J.F.W. Herschel, and Franz Xaver von Zach; the conchologists A.D. Brown, Fred L. Button, Otto Mörch, Alfred Newton, Christian M. Poulsen, Temple Prime, Benjamin Lewis Vulliamy, and A. G. Wetherby; the physical scientists George Biddell Airy, Arnold Sommerfeld, Ferdinand R. Hassler, and Max Planck; the archaeologist Jean François Nadaillac; the philosopher William Whewell; and the naturalists Walter Henry Bates, Robert Chambers, Edme Dupuget, Robert Kaye Greville, Joseph Henry, John Stevens Henslow, John Lubbock, and Herbert Spencer.

One of the most important natural historians in nineteenth century Britain, Charles Darwin provided the first compelling mechanism to account for organismal evolutionary change. Although lacking a coherent model of heredity, Darwin's natural selection has exerted an enormous influence over the biological sciences and since the introduction of Mendelian genetics, had remained the key unifying principle in the discipline. The APS Darwin Papers are a large a valuable assemblage of Darwin's correspondence with scientific colleagues, including Charles Lyell and George J. Romanes. They are included in the print version of the Correspondence of Charles Darwin (Cambridge Univ. Press).

Arthur J. Cain is an evolutionary biologist whose research interests have included genetics, natural selection, biogeography, and systematics. Based at Oxford University and, later, the University of Liverpool, much of Cain's research was field-based, focusing on terrestrial gatsropods. This collection contains correspondence, grant applications, reports, programs for scientific meetings, unpublished papers and lectures, research notes, charts, graphs, maps, and manuscript reviews of journal articles and books. The Cain Papers is divided into three series: I. Correspondence ; II. Subject Files ; and, III. Papers by Colleagues. Arrangement is alphabetical by folder title, and chronological within each folder.

The population geneticist Hampton L. Carson spent the major part of his career at Washington University (1949-1963) and the University of Hawaii (1963-1985) investigating the cytogenetics and evolution of Drosophila. As one of the major figures in the Hawaii Drosophila project, he made particularly important contributions to the study of speciation and selective and non-selective evolutionary mechanisms. The Carson Papers (1921-1993) contain correspondence, subject files, manuscripts of published and unpublished works by Carson, papers by colleagues and students, research notes, course materials, photographs, and biographical information, which documents Carson's career as an evolutionary geneticist. The collection is organized into nine series.

One of the seminal figures in the emergence of the Modern or Neo-Darwinian Synthesis during the mid-twentieth century, George Gaylord Simpson (1902-1984) helped define the unique contribution made by vertebrate paleontology to the life sciences. A specialist in Mesozoic and early Cenozoic mammals, Simpson's contributions to the fusion of Darwinian natural selection and Mendelian genetics were both empirical and theoretical, culminating in his major works Tempo and Mode in Evolution and The Meaning of Evolution. From his posts at the American Museum of Natural History (1927-1959), Columbia University (1945-1959), Harvard (1959-1967), and the University of Arizona (1967-1984), Simpson became one of the most influential paleontologists of the century, helped in part by his ability to write successfully for both a technical, professional audience and a popular audience. The Simpson Papers include a comprehensive assemblage of professional and personal correspondence, reflecting nealy all phases of Simpson's career. Written with charm, wit, and a sense of literary style, the correspondence touches on all aspects of modern paleontology, providing an important perspective on the emergence of contemporary evolutionary theory, biogeography, systematic theory and methodology, the relationship of science and religion, and creationism, as well as more general issues in scientific epistemology and social and political issues. The collection also includes autobiographical data and writings, lectures, class notes and papers, research data, material on his scientific expeditions (diaries in carbon form, photos, notes, etc.), publication material (he was author of some 800 publications), extensive photographic material, diplomas, and medals.

A geneticist and educator, Philip Macdonald Sheppard was head of the Department of Genetics at the University of Liverpool from 1963-1976. His research centered on polymorphism, mimicry, blood groups, genetic disease, and speciation, using a variety of subjects, including the gastropod Cepaea nemoralis, butterflies, and humans. He may be best remembered for his classic study of industrial melanism in the pepper moth Biston betularia. The Sheppard Papers (1911-1983; bulk dates, 1940-76) contain correspondence, subject files, notes, and manuscripts that document Sheppard's life as a geneticist. The earliest piece in the collection is a lepidopterist's notebook from 1911, possibly J. R. Hobhouse's, however the bulk dates from 1940 to 1976, Sheppard's most productive and influential years. Among other things, these materials document Sheppard's research on the Scarlet Tiger moth, swallowtail butterflies, and ABO blood groups in humans, as well as his position as head of the Department of Genetics at the University of Liverpool.

Sewall Wright ranks among the most influential figures in the field of population genetics during the 20th century, and made important contributions to biostatistics, biometrics, and evolutionary theory. These papers contain much of Wright's professional correspondence, scattered research notes, and drafts of a small number of papers.