The Man Who Invented the Chromosome: A Life of Cyril Darlington

  • Oren Solomon Harman
Harvard University Press, 2004 329 pp., hardcover, $49.95 ISBN 0674013336 | ISBN: 0-674-01333-6

Cyril Darlington was the leading cytologist in Britain between 1930 and 1950, and a major figure in the British genetics community, as well-known for his cantankerous personality as for his science. The title of this biography is misleading; Darlington did not invent, or even discover, the chromosome. In his heyday, however, he did have a great deal of influence on people's thinking about cytology, genetics and evolution. This influence has largely faded, as Harman acknowledges in his introduction to the book. Overall, Harman has done an excellent job of portraying Darlington's stormy personal and scientific life, bringing out his flaws as well as his achievements. Harman is, I think, less successful at evaluating Darlington's scientific contributions, and putting them into historical perspective.

After a difficult and impoverished childhood and adolescence, Darlington started his career as a Ph.D. student at the John Innes Institute in 1923, at the close of the reign of director William Bateson. The institute was then the leading place for genetics research in England, owing to the hidebound attitude of most university biologists toward the new field. However, Bateson himself had been left behind by the rapid advances in genetics and cytology between 1910 and 1925, led by T.H. Morgan's Drosophila group. His mutationist views on evolution were also at odds with the new work on population genetics, represented in Britain by R.A. Fisher and J.B.S. Haldane—who was recruited to John Innes part-time, and clearly provided an enormous stimulant to Darlington's intellectual development.

During this period, Darlington did his most important research, which culminated in his 1931 book Recent Advances in Cytology. He made a strong case for the equivalence of the cytologically visible chiasmata and genetic crossovers, something which is largely taken for granted nowadays, but which was widely doubted before 1930. In addition, he argued that chiasmata were necessary for the disjunction of chromosomes at the first division of meiosis. Though subject to a number of qualifications, such as the absence of chiasmata in the heterogametic sex in several groups (such as male Drosophila), this generalization has stood the test of time. He also clarified the role of reciprocal translocations in the unusual genetic and cytological behavior of the evening primrose, Oenothera, probably the most bizarre genetic system we know of.

As Harman makes clear, many of Darlington's ideas aroused the wrath of the older generation of cytologists. This reflects his characteristic mode of doing science: to propose hypotheses without having detailed evidence to back them up. For this reason, Darlington cannot be regarded as the scientific equal of the members of the Drosophila group, who habitually conducted careful experiments to test their ideas to the limit. As an evolutionary theorist, too, he had serious shortcomings. These are exemplified by his well-known book The Evolution of Genetic Systems, first published in 1939 with a second edition in 1958. This had the great merit, however, of drawing attention to a wide range of important questions concerning the evolution of sexual versus asexual reproduction, meiosis, genetic recombination, inbreeding versus outbreeding, and many other topics.

As a student in the 1960s, I remember acquiring the book in the hope of learning how these fundamentally important aspects of living systems had evolved. I was, however, disappointed by the nature of Darlington's explanations. These are mainly based on the idea that the properties of the genetic system confer advantages at the level of the population or the species, as opposed to individuals or genotypes within a population. Despite his close contacts with Haldane until the mid-1930s, Darlington made no attempt to use the methods of population genetics to explain the phenomena that he described so brilliantly. Darlington's group-selectionist approach to genetic systems dominated thinking on the subject for nearly three decades. It stultified theoretical and empirical work on genetic and sexual systems until the 1970s, when approaches based on population genetics started to displace the old ideas. Harman, perhaps because of his admiration for Darlington, does not delve into this aspect of his influence.

The later part of Darlington's career had some almost tragic aspects, and he made few original research contributions after the 1930s. In 1939, he become director of the John Innes Institute, a post greatly coveted by Haldane, with whom he fell out. It is greatly to Darlington's credit that he took an active role in exposing the ruin of genetics in the Soviet Union under Trofim Lysenko, who used his political influence to impose erroneous theories of the inheritance of acquired characteristics on Soviet biology and agronomy. This contrasted with Haldane's rather shifty attitude. Darlington moved to Oxford in 1953 with the aim of introducing genetics into the world's most famously conservative university—but he conspicuously lacked the diplomatic skills needed to succeed in this. He became interested in applying genetics to social questions, and published several books arguing for the strong genetic determination of human cultural differences. Although he was probably not a true racist, his views could certainly be used by racists, and he made many statements that seem at best extraordinarily short-sighted. Most of his peers in the field of genetics disagreed strongly with his ideas. He became an increasingly isolated figure, who was devastated by the suicide in 1970 of his son Andrew, a very promising young geneticist. His last years were spent in retirement, with his early, substantial achievements having been overtaken by the subsequent rapid development of genetics.