Stebbins, George Ledyard, Jr
STEBBINS, GEORGE LEDYARD, JR
(b. Lawrence, New York, 6 January 1906; d. Davis, California, 19 January 2000), botany, genetics, evolutionary biology.
Stebbins is best known as one of the architects of the “evolutionary synthesis” of the 1930s and 1940s. His primary contribution to the incorporation of Mendelian genetics with Darwinian evolutionary theory was the publication of his 1950 book, Variation and Evolution in Plants, which brought understanding of plant evolution in line with understanding of animal evolution as it was being formulated during the period of synthesis. Stebbins is also known for his varied contributions in areas of systematic botany, plant geography, cytogenetics, plant breeding, and plant developmental biology, but is generally recognized as the pioneer of the field of plant evolutionary biology, which incorporated elements from all these areas. He was the master of the synthetic review article and is especially remembered for his contributions to general understanding of phenomena such as polyploidy, apomixis (a form of asexual fertilization), and hybridization, especially as they played out in the pattern and process of evolution in the plant world.
Family Background and Education George Ledyard Stebbins Jr. was born in Lawrence, New York, the son of George Ledyard Stebbins of Cazenovia, New York, and Edith Alden Candler of Brooklyn, New York. His father was a wealthy New York financier and real estate developer who was responsible for developing the resort town of Seal Harbor, Maine. He was also instrumental in helping to create Acadia National Park on Mount Desert Island, Maine. His mother was a New York socialite whose brother Duncan was a popular architect known for his connections with New York elites. Ledyard (as he preferred to be called) Stebbins was named after his father, and until shortly after his father’s death in 1950 used “junior” after his surname. He was the third offspring in the family. His older brother Henry became a popular physician in Seal Harbor and his older sister Marcia became an artist.
Stebbins showed an early interest in natural history generally, and plant life in particular, which his family encouraged. Both of his parents took their children out for nature walks, canoe rides, and hikes along the shorelines, mountains, and tide pools in Maine. The resort life of Seal Harbor, which was popular with northeastern intellectuals, also brought the Stebbins children in contact with scientists such as Edgar T. Wherry, an expert on ferns. Stebbins later credited Wherry with his initial interest in the plants of Maine.
In 1914 the entire family relocated to the West Coast when Edith Stebbins contracted tuberculosis. Ledyard Stebbins was enrolled at the Polytechnic School in Pasadena, California. His early educational career was undistinguished, though he did excel at outdoor activities such as hiking, mountaineering, and horseback riding. In 1917 the family was forced to move to Colorado Springs, Colorado, so that Edith Stebbins could be treated at Crag-more Sanitarium. Ledyard and his brother Henry enrolled in St. Stephen’s school for boys, a school known for its outdoors activities; there his interests in natural history were further nurtured. In 1920 the family returned to California and settled in Santa Barbara, where Ledyard was enrolled at the Cate School in Carpinteria.
In 1924 Stebbins followed his older brother to Harvard University, with loose plans to major in political science in the hope of obtaining a law degree. He changed his mind after a summer of botanizing on Mount Desert Island and after he had fallen under the influence of the distinguished plant taxonomist at Harvard, Merritt Lyndon Fernald, who was then preparing the eighth, or “centennial edition” of Gray’s Manual of Botany. Taking Fernald’s “Botany 7” course, the Flora of New England and the Maritime Provinces of Canada, Stebbins accompanied him on field trips, became an expert on floristics, and fell under the influence of Fernald’s controversial “nunatak theory,” a biogeographic theory based on the distribution of glacial relicts, popular at the time. Despite some initial parental disapproval (they were concerned about his employment prospects and financial hardship), Stebbins enrolled formally in Harvard’s graduate program in 1928 with the intention of training in botany. From approximately 1926 until 1929, Stebbins worked closely with Fernald on the taxonomy of the New England flora. He completed several taxonomic studies but switched his emphasis—and his advisor—when he turned to the newer area of plant cytology, working closely with the Harvard morphologist and anatomist Edward Charles Jeffrey.
His dissertation topic focused on the cytology (cellular structure and function) of geographic variants of the plant Antennaria. Toward the end of his dissertation research, he sought the aid of Karl Sax, the new geneticist hired at the Arnold Arboretum. Sax, trained in the most recent genetics techniques, made a number of important suggestions to the research on Antennaria and included at least one important correction on the orientation of the chromosomes, which Stebbins had incorrectly interpreted. Sax’s last minute intervention in the dissertation was not well taken by Jeffrey, however, and the dissertation committee nearly fell apart but for the well-timed intervention of the chair of the department, Oakes Ames, and the mediation skills of the developmental morphologist, Ralph Wetmore. Only after the dissertation was rewritten a number of times was it finally accepted and the degree granted in 1931. The completed dissertation, which drew on a disparate set of approaches that were uncommon for a systematic project at the time, formed the backbone of Stebbins’s subsequent cytologic and systematic studies. It also demonstrated what became a lifelong tendency to cross barriers in discipline, methodology, and even interpersonal relationships in the spirit of synthesis.
Scientific Career: Botanist, Geneticist, and Evolutionist In 1932 Stebbins took a position as teacher of biology at Colgate University in Hamilton, New York. Though he did not have much time for research, he continued to refine his expertise in cytogenetics, the new science that concentrated on chromosomes and integrated cytology with genetics. He collaborated closely with Percy Saunders, of the famous Canadian family of wheat breeders, at nearby Hamilton College. Saunders’s passion was breeding hybrid peonies, which he grew in his backyard and which were used for his cytological studies conducted out of his home laboratory. With Saunders, Stebbins attended the 1932 International Congress of Genetics in nearby Ithaca, New York, which exposed him to the work of geneticists such as Cyril Dean Darlington and Barbara McClintock as well as evolutionists such as Sewall Wright.
In 1935 the opportunity to pursue scientific research in genetics full-time was realized when Stebbins accepted a position as junior geneticist to the botanist Ernest Brown Babcock, at the University of California, Berkeley. At that time, Babcock was working on an ambitious project to understand the genetics of the evolutionary process in the genus Crepis. It was Babcock’s hope that Crepis would function much as Drosophila had in serving as a model organism that lent itself to study in evolutionary genetics. Working as Babcock’s assistant, Stebbins applied much of what he had learned in cytogenetics and systematics to the new genus. Together, Babcock and Stebbins published a series of important articles and a monograph titled The American Species of Crepis: Their Interrelationships and Distribution as Affected by Polyploidy and Apomixis in 1938. Their most notable contribution was in articulating the notion of “the polyploid complex” (sometimes also called “the agamic complex”), a geographic complex of reproductive forms that centered on diploids fringed by apomictic or asexual forms. It was the most complete analysis of the interplay of polyploidy, apomixis, and hybridization with geographic and systematic considerations for any plant genus known at the time. It also offered insights into species formation, polymorphy in apomictic forms, and knowledge of how all these complex processes could inform an accurate phylogenetic history of the genus. Stebbins later extended these ideas further with subsequent breeding in forage grasses and published a series of important articles in 1940, 1941, and 1947. The latter article, “Types of Polyploids: Their Classification and Significance,” became a widely read review that synthesized knowledge of polyploidy; it is still regarded as a major contribution to understanding of plant evolutionary biology.
Stebbins worked with Babcock for some six years and in 1939, with Babcock’s support, he was hired as full-time assistant professor in the department of genetics at the University of California, Berkeley. He also took over teaching the general course in evolution when the opportunity arose. In preparation for this course, Stebbins read the evolution literature widely and was quickly exposed to the exciting new literature incorporating genetics and evolutionary studies. He was part of a fortnightly journal club in genetics, called Genetics Associated, that included the émigré geneticist Isadore Michael Lerner. Lerner, in turn, introduced him to his Russian colleague Theodosius Dobzhansky, who was then working with Thomas Hunt Morgan at the California Institute of Technology. Stebbins interacted with Lerner and Dobzhansky, but also with a small but growing circle of systematists in the San Francisco Bay Area who were turning their interests to what they hailed as the “new” systematics, built on current ideas that drew on genetics and evolution; they later called themselves the Biosystematists. The group included leading botanists in the Bay Area such as the Danish genecologist Jens Clausen but also visitors such as the botanists Edgar Anderson from the Missouri Botanical Garden and Carl Epling from the University of California at Los Angeles. With their encouragement, Stebbins pursued evolutionary research closely and incorporated their insights into plant evolution, but he also read widely on the animal side of evolution. By the early 1940s he was one of the few botanists easily conversant with the disparate literature in genetics, ecology, systematics, cytology, and paleontology in both the animal and the plant world. His growing friendship with Dobzhansky, which was reinforced by collecting trips at Mather, California, also proved to be especially important.
The opportunity to draw all the disparate branches together in a synthesis in understanding mechanisms and patterns of plant evolution came in 1946, when Stebbins was invited on the recommendation of Dobzhansky to deliver Columbia University’s prestigious Jesup Lectures. In 1950 the lectures were published in book form as Variation and Evolution in Plants, which proved to be one of the most important books published in twentieth-century American botany because of its synthetic breadth; it also led to a virtual revolution in understanding plant evolution so that it became the foundational text of the field that was eventually known as plant evolutionary biology. It became part of the canon of biological works written between 1936 and 1950 that formed the backbone of the “modern synthesis of evolution” or the historical event known as the “evolutionary synthesis.” From 1950 on, Stebbins became one of the most visible experts on the science of modern evolutionary biology and the person generally credited with founding the science of evolutionary botany or plant evolutionary biology.
In 1950 Stebbins moved to the newer campus of the University of California, Davis, where he was assigned the task of building a new Department of Genetics. His own research interests shifted appreciably to areas associated with development biology and developmental genetics, eventually incorporating newer techniques from plant molecular biology into his research program. Through the 1950s and 1960s he trained more than thirty graduate students, most of whom were in genetics, developmental biology, or agricultural science.
Throughout the course of his scientific career, Stebbins showed a remarkable ability to understand new problems and to apply new techniques. Unlike most botanists, Stebbins worked on a staggering range of plant organisms, from grasses to peonies to members of the daisy family. He published extensively in systematics, morphology, cytology, genetics, plant geography, and developmental biology. Neither fish nor fowl, Stebbins frequently failed to receive credit for work in some of these areas, however, usually at the hands of narrower colleagues. Systematists felt that he concentrated too heavily on genetics and too lightly on taxonomic studies of a special set of organisms; geneticists, in contrast, felt that his work was too evolutionary and natural history–oriented and that it did not concentrate sufficiently on understanding mechanisms of gene action. Few, however, have challenged his contributions to plant evolutionary biology, nor questioned his ability to synthesize disparate literature that he could place into a coherent framework, a feat he achieved repeatedly over the course of his long career. His publication list includes a staggering number of review articles that reflect his ability to command new literature and to synthesize disparate information. In 1965, for example, he and the Berkeley botanist Herbert Baker edited Genetics of Colonizing Species. This was to prove a pioneering work in what would later be called the science of “invasion biology.” In 1974 he brought much of his life-long knowledge of plant evolution to bear on the complex problem of angiosperm evolution in his influential Flowering Plants: Evolution above the Species Level. Stebbins continued to read widely and to publish such synthetic works, though in a diminished capacity, up until the time of his death.
His influence increasingly extended outside research science, especially after the publication of his 1950 book. He became active in organizations such as the International Union of Biological Sciences. He served as president of the American Society of Naturalists, the Western Society of Naturalists, the Botanical Society of America, and the Society for the Study of Evolution. He was a member of the National Academy of Sciences and in 1980 received the National Medal of Science from President Jimmy Carter. Throughout the 1960s and the 1970s he was an active defender of evolution against creationist assaults of varied types. He worked closely with the Biological Sciences and Curriculum Study (BSCS) to develop curricula at the high school level built on evolution as the central unifying principle in biology. Stebbins contributed to the teaching of evolution even more heavily by writing textbooks and semipopular books of science, and through many public lectures.
Yet another area of interest was in conservation, which proved a lifelong passion. In the 1960s Stebbins was instrumental in helping to create the California Native Plant Society, for which he served as president in 1967. He organized numerous field trips that included amateurs and students, and fought tirelessly to protect ecologically sensitive areas such as a well-known strip of raised beach on the Monterey Peninsula. For his work in conservation and in evolutionary science the University of California, Davis, paid him a rare honor, naming a 227-acre preserve near Lake Beryessa, California, the Stebbins Cold Canyon Reserve.
Stebbins was married twice. His first marriage ended in divorce but produced three children, Edith, Robert, and George. Stebbins remarried in the 1950s. His second wife, Barbara, had one son by a previous marriage; she died suddenly in 1993 while accompanying Stebbins on a lecture tour.
Stebbins became emeritus professor of genetics in 1973 but continued to lecture, publish, and travel widely until a series of debilitating diseases in the 1990s bound him to Davis. He died there as a result of cancer.
WORKS BY STEBBINS
With Ernest B. Babcock. The American Species of Crepis: Their Interrelationships and Distribution as Affected by Polyploidy and Apomixis. Washington, DC: Carnegie Institution of Washington, 1938.
“The Significance of Polyploidy in Plant Evolution.” American Naturalist 74 (1940): 54–66.
“Apomixis in the Angiosperms.” Botanical Review 7 (1941): 507–542.
“Types of Polyploids: Their Classification and Significance.” Advances in Genetics 1 (1947): 403–429.
Variation and Evolution in Plants. New York: Columbia University Press, 1950.
With Herbert G. Baker, eds. Genetics of Colonizing Species: Proceedings of the First International Union of Biological Sciences Symposia on General Biology. New York: Academic Press, 1965.
Flowering Plants: Evolution above the Species Level. Cambridge, MA: Belknap Press, 1974.
The Scientific Papers of G. Ledyard Stebbins: (1929–2000). Edited by Daniel J. Crawford and Vassiliki Betty Smocovitis. Regnum Vegetabile, vol. 142. Ruggell, Liechtenstein: Gantner, 2004. A complete list of publications by G. Ledyard Stebbins is included here.
The Lady Slipper and I. Edited by Vassiliki Betty Smocovitis, Victoria Hollowell, and Eileen Duggan. St. Louis: Missouri Botanical Garden Press, 2007. This is an autobiography left uncompleted at the time of his death.
Bradshaw, Anthony, and Vassiliki Betty Smocovitis. “G. Ledyard Stebbins.” Biographical Memoirs of Fellows of the Royal Society51 (2005): 397–408.
Faber, Phyllis M. “G. Ledyard Stebbins Jr., 1906–2000.” Fremontia 28 (2000): 69–70.
Smocovitis, Vassiliki Betty. “Botany and the Evolutionary Synthesis: The Life and Work of G. Ledyard Stebbins Jr.” PhD diss., Cornell University, 1988.
———. “G. Ledyard Stebbins Jr. and the Evolutionary Synthesis (1924–1950).” American Journal of Botany 84 (1997): 1625–1637.
———. “Living with Your Biographical Subject: Problems of Distance, Privacy, and Trust in the Writing of the Biography of G. Ledyard Stebbins, Jr.” Journal of the History of Biology32 (1999): 421–438.
———. “G. Ledyard Stebbins and the Evolutionary Synthesis.”Annual Review of Genetics 35 (2001): 803–814.
———. “Keeping up with Dobzhansky: G. Ledyard Stebbins, Plant Evolution, and the Evolutionary Synthesis.” History and Philosophy of the Life Sciences 28 (2006): 11– 50.
Smocovitis, Vassiliki Betty, and Francisco Ayala. “G. Ledyard Stebbins (1906–2000).” Biographical Memoirs of the National Academy of Sciences 85 (2004): 3–24.
Solbrig, Otto. “George Ledyard Stebbins.” In Topics in Plant Population Biology, edited by Otto Solbrig, Subodh Jain, George B. Johnson, et al., 1–17. New York: Columbia University Press, 1979.
Vassiliki Betty Smocovitis