After Cambridge, he became a schoolmaster at Dartington Hall School, Devonshire until Summer 1938 when he took a year off to study bird behaviour on the Galapagos Islands. He was only in the Galapagos for part of that year, starting August 1938. April to August 1939 was spent at the California Academy of Sciences and at Ernst Mayr's home in New Jersey. He returned home in September 1939, after the outbreak of war.
During World War II Lack served in the British Army working on radar research. After hostilities ended he was made Director of the Edward Grey Institute of Field Ornithology at Oxford University (1945—1973). His wartime experience enabled him to make radar observations of bird migration.
Lack's work in ornithology was almost entirely based on studies of the
living bird. He was one of the pioneers of life-history studies in Britain, especially those based on quantitative approaches, when some traditional ornithologists of the time were focussing their studies on morphology and geographic distribution. Lack's major scientific research included work on population biology and density dependent regulation. His work suggested that natural selection favoured clutch sizes that ensured the greatest number of surviving young. This interpretation was however debated by V.C. Wynne-Edwards who suggested that clutch-size was density-independent. This was one of the earliest debates on group selection. Lack's studies were based on nidicolous birds and some recent studies have suggested that this may not hold for other groups such as seabirds.
He wrote numerous papers in ornithological journals, and had a knack of choosing memorable titles: he once claimed to have single-handedly caused the renaming of a group of birds through the submission of a scientific paper, his 1935 publication, "Territory and polygamy in a bishop bird,
Euplectes hordeacea hordeacea (Linn.)" in the journal
Ibis. Up to that point birds in the genus
Euplectes had been referred to simply as bishops, but the journal editor felt that with that form the title might cause misunderstanding.
Darwin's finches
Lack's most famous work is
Darwin's Finches, a landmark study whose title linked Darwin's name with the Galapagos group of species and popularised the term "Darwin's finches" in 1961, though the term had been introduced by Percy Lowe in 1936. It is often forgotten that there are two versions of this work, and they differ significantly in their conclusions. The first is a book-length monograph, written after his visit to the Galapagos, but not published until 1945. In it Lack interprets the differences in bill size as species recognition signals, that is, as isolating mechanisms.
The second is the later book in which the differences in bill size are interpreted as adaptations to specific food niches, an interpretation that has since been abundantly confirmed. This change of mind, according to Lack's Preface, came about as a result of his reflections on his own data whilst he was doing war work. The effect of this change in interpretation is to put the emphasis for speciation onto natural selection for appropriate food handling instead of seeing it primarily as a by-product of an isolating mechanism. In this way his work contributed to the modern evolutionary synthesis, in which natural selection came to be seen as the prime mover in evolution, and not random or mutational events. Lack's work laid the foundations for the much more extensive work of Peter Grant and his colleagues. Also, Lack's work feeds into studies of island biogeography which continue the same range of issues presented by the Galapagos fauna on a more varied canvas.
- "The person who more than anyone else deserves credit for reviving an interest in the ecological significance of species was David Lack... It is now quite clear that the process of speciation is not completed by the acquisition of isolating mechanisms but requires also the acquisition of adaptations that permit co-existence with potential competitors."
Religious beliefs
Lack became a convert to Anglicanism, which led to his composition, in 1957, of a brief book,
Evolutionary theory and Christian belief, on the relationship between Christian faith and evolutionary theory. This book foreshadows, in some ways, the non-overlapping magisteria conception of the relationship between religion and science later popularized by Stephen Jay Gould.
Arthur Cain remarked of him "David Lack was the only religious man I knew at that period who did not allow his religion to dictate his view of natural selection."
Career outline
- 1933—1940: biology master at Dartington Hall School
- 1940: study visit to the Galapagos Islands
- 1940—1945: work on radar development
- 1945—1973: Director of the Edward Grey Institute of Field Ornithology, Oxford.
- 1948: ScD, Magdalene College, Cambridge
- 1963: Fellow of Trinity College, Oxford
- 1972: awarded Darwin Medal of the Royal Society
- 1973: dies at Oxford, 12 March 1973.