LACK, DAVID LAMBERT

(b. London, England, 16 July 1910; d. Oxford, England, 12 March 1973)

ornithology, ecology, ethology.

David Lack was the eldest of the four children of Harry Lambert Lack, a leading ear, nose, and throat surgeon in London, and of Kathleen Rind, a professional actress before her marriage. He was educated at Gresham’s School, Holt, Norfolk, and in 1929 entered Magdalene College, Cambridge, where he completed the natural sciences tripos and graduated in June 1933. He was steered by Julian Huxley to a position as biology teacher at a progressive Devonshire school, Dartington Hall. After a leave of absence spent in the Galapagos (1938–1939), he resigned from the school at the end of the academic year in 1940, having grown disenchanted with its educational philosophy.

From 1940 to 1945 Lack was involved in warrelated work as a civilian. From 1945 on, he was director of the Edward Grey Institute of Field Ornithology at Oxford in 1963; he became professorial fellow of Trinity College, Oxford. He was elected to the Royal Society of London in 1951, served as president of the Fourteenth International Ornithological Congress in 1966, and was awarded the Darwin Medal of the Royal Society in 1972.

On 9 July 1949 Lack married Elizabeth Twemlow Silva, who collaborated with him in his research and was still active in ornithology at Oxford in the late 1980’s. They had three sons and a daughter. He converted to the Anglican religion in 1948 from an agnostic stance and was confirmed in 1951. In addition to his scientific research, Lack wrote several books on the natural history of birds for a more general audience.

As an ornithologist and committed Darwinian, Lack was instrumental in forming and promoting a synthesis of evolutionary biology and ecology, and in developing the field of population ecology, From adolescence his dominant enthusiasms were birds and evolution, the latter interest stimulated by W. P. Pycraft’s popular books. He also read Huxley’s articles on bird courtship while in high school. At Cambridge, Lack was influenced by J. B. S. Haldane and Ronald A. Fisher, though he did not adopt the mathematical methods of these theorists. At Dartington Hall he pursued his research on bird ecology and behavior. As a member of the Scientific Advisory Committee of the British Trust for Ornithology (formed in 1932), he helped to organize a heathland census inquiry in 1933. Through this work he became interested in territorial behavior of the European robin.

During the 1930’s Huxley acted as Lack’s unofficial supervisor, eventually securing grants from the Royal Society and the Zoological Society of London to finance an expedition of Lack and others to the Galapagos Islands in the fall of 1938. During his leave of absence (1938–1939) Lack investigated speciation in the Galapagos finches, spending five months studying museum collections in the United States. The California Academy of Sciences, owner of the largest collection, published his first monograph on the finches, with a four-year delay after his submission of the manuscript, in 1945. However it was not this work but his second book on these birds, Darwin’s Finches, published in 1947, that brought Lack worldwide attention. The book is now regarded as a classic of evolutionary biology.

Darwin’s Finches is a lucid study of the importance of ecological factors in promoting divergence among closely related species. It was commonly thought in the 1930’s that minor differences between similar species were not adaptive, thereby setting a limit to the role of natural selection in originating species. Using the finches as a paradigm, Lack argued to the contrary: that most of the minor differences between these species were adaptations produced by natural selection, which enabled the species to avoid competing with each other for food. Lack’s views in this book were a reversal of what he had written in his first monograph. His change of mind came after reflecting on the implications of a principle discussed by the Russian ecologist G. F. Gause in the 1930’s: that two competing species cannot occupy identical ecological niches. Lack’s development of what is now known as the “competitive exclusion principle” stimulated a great deal of experimental research on competition and adaptation, and contributed to a greater awareness among biologists in the 1960’s of the subtlety of natural selection. Lack’s conversion was influenced by conversations with the entomologist George C. Varley on the mechanisms of population regulation. His new interpretations interested Ernst Mayr, his close friend, who invited Lack to present them at a Princeton University conference on evolutionary biology in 1947.

Lack dated his conversion on the Galapagos finches to 1943, when he was touring coastal shipwatching radar stations in connection with his work for the Operational Research Group. His companion, Varley, discovered that birds were detected by radar, and Lack henceforth made effective use of radar in studies of bird migration. Also in 1943 he had his second major scientific idea, which concerned the evolution of reproductive rates in birds. He argued that clutch size was adjusted not to mortality or to the physiological capability of birds, but to the food supply available to the parents to feed their young. He especially objected to the teleological nature of arguments that saw clutch size as compensation for mortality. His theory maintained that natural selection would regulate clutch size so as to produce the greatest number of young surviving to independence. These ideas were developed in the context of debates in the growing field of population ecology over mechanisms of population regulation. The basic choice among causes of regulation was between biotic factors (predation, food supply), which varied in severity in proportion to population density, and abiotic factors (climate), whose severity was largely independent of a population’s density. Lack’s research, published in 1954 in The Natural Regulation of Animal Numbers, supported the primacy of density-dependent regulation. His argument was influenced by the theories of the Australian entomologist A. J. Nicholson. This issue became the focus of intense ecological discussion in the 1960’s.

Lack’s ideas about natural selection led to a further controversy with V. C. Wynne-Edwards, who in 1962 published Animal Dispersion in Relation to Social Behaviour, in which he applied the theory of “group selection,” the idea that natural selection could actually override the interests of the individual by working on features that benefited the group as a whole. Lack’s response to Wynne-Edwards and his criticisms of group selection appeared in Population Studies of Birds (1966).

Lack’s conversion to Christianity resulted in his 1957 book Evolutionary Theory and Christian Belief; it met with a poor reception among his colleagues. Unlike those who were interested in reconciling science and religion. Lack had no qualms about embracing orthodox religious beliefs that appeared to be in contradiction with his scientific views about evolution. He felt no such contradiction, however.

As director of the Edward Grey Institute. Lack devoted his energies to problems of population regulation. turning his institute into a world center for population ecology. In research his emphasis was always on field observation and comparative surveys. rather than on experiment. He distrusted the artificial conditions imposed by experiments and had a deep aversion to any research that involved killing birds. He often presented an argument by gathering facts from field studies until the sheer weight of the evidence supported whatever position he had adopted. In this respect his style was similar to Darwin’s. He also distrusted the often crude mathematical approaches to ecology that had become prominent in the 1960’s. His last book, Island Biology. published posthumously in 1976, was partly a response to the mathematical theory of biogeography introduced by Robert H. MacArthur and Edward O. Wilson in The Theory of Island Biogeography (1967).

Lack was first and foremost a naturalist who sought to combine problems in animal behavior, ecology. and evolutionary biology. He may justly be counted among the small group of naturalists, including Huxley and Mayr. who contributed to the “modern synthesis” in evolutionary biology in the middle decades of the twentieth century.

BIBLIOGRAPHY

I. Original Works. A nearly complete bibiography is in the memoir by W. H. Thorpe in Biographical Memoirs of Fellows of the Royal Society of London, 20 (1974), 271–293. Darwin’s Finches has been republished with notes and an introduction by Laurene M. Ratcliffe and Peter T. Boag (Cambridge, 1983). Competitive exclusion was the subject of several articles by Lack, the first being “Ecological Aspects of Species-formation in Passerine Birds,” in Ibis. 86 (1944), 260–286. His first public presentation of his change of view is reported in the symposium on the ecology of closely allied species, in Journal of Animal Ecology, 13 (1944), 176–177. See also “The Significance of Ecological Isolation,” in G. L. Jepsen et al., eds., Genetics. Paleontology, and Evolution (Princeton. 1949), 299–308. These ideas are extended in Ecological Isolation in Birds (Oxford and Edinburgh, 1971). Lack’s position in the controversies on population regulation and animal dispersion is explained in his appendix to population Studies of Birds (Oxford, 1966). His major original work on reproductive rates is The Natural Regulation of Animal Numbers (Oxford, 1954). His posthumous book is Island Biology, Illustrated by the Land Birds of Jamaica (Berkeley and Los Angeles, 1976).

Lack’s general writings on natural history include The Life of the Robin (London, 1943: rev. ed., 1946; paperback ed., 1953: 4th ed., 1965); and Swifts in a Tower (London, 1956; repr. 1973).

Lack’s memoirs of his life to 1945. “My Life as an Amateur Ornithologist,” with some reminiscences from several colleagues, are in Ibis. 115 (1973). 421–441. Archival material, including scientific correspondence relating to his publications, is at the Edward Grey Library of Field Ornithology. Oxford University.

II. Secondary Literature. The fullest account of his life, based heavily on Lackx2019;s own memoir, is by W. H. Thorpe (see above). For contemporary assessments of his work. see Denis Chitty, “Population Studies and Scientific Methodology,” in British Journal for the philosophy of Science, 8 (1957), 64–66; and Gordon H. Orians, “Natural Selection and Ecological Theory,” in American Nat-uralist, 96 1962, 257–263. Of further interest are Frank J. Sulloway, “Darwin and His Finches: The Evolution of a Legend,” in Journal of the History of Biology, 15 (1982), 1–53; and Marjorie Grene, ed., Dimensions of Darwinism: The mes and Counterthemes in TwentiethCentury Evolutionary Theory (Cambridge. 1983), essays by William B. Provine, “The Development of Wright’s Theory of Evolution: Systematics, Adaptation, and Drift,” and by Stephen Jay Gould. “The Hardening of the Modern Synthesis.”

Sharon Kingsland