national academy of sciences

Theodosius Dobzhansky

1900—1975

A Biographical Memoir byfrancisco j. ayala

Any opinions expressed in this memoir are those of the author(s)and do not necessarily reflect the views of the
National Academy of Sciences.

Biographical Memoir
Copyright 1985
national academy of sciences
washington d.c.

THEODOSIUS DOBZHANSKY
January 25, 1900-December 18, 1975
BY FRANCISCO J. AYALATHEODOSIUS DOBZHANSKY was born on January 25, 1900

in Nemirov, a small town 200 kilometers southeast ofKiev in the Ukraine. He was the only child of Sophia
Voinarsky and Grigory Dobrzhansky (precise transliterationof the Russian family name includes the letter "r"), a teacher
of high school mathematics. In 1910 the family moved to theoutskirts of Kiev, where Dobzhansky lived through thetumultuous years of World War I and the Bolshevik revolution. These were years when the family was at times beset byvarious privations, including hunger.
In his unpublished autobiographical Reminiscences for theOral History Project of Columbia University, Dobzhansky
states that his decision to become a biologist was madearound 1912. Through his early high school (Gymnasium)
years, Dobzhansky became an avid butterfly collector. A
schoolteacher gave him access to a microscope that Dobzhansky used, particularly during the long winter months. In
the winter of 1915—1916, he met Victor Luchnik, a twentyfive-year-old college dropout, who was a dedicated entomologist specializing in Coccinellidae beetles. Luchnik convinced
Dobzhansky that butterfly collecting would not lead anywhere, that he should become a specialist. Dobzhansky chose
to work with ladybird beetles, which would be the subject of
his first scientific publication in 1918.
163

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BIOGRAPHICAL MEMOIRSDobzhansky graduated in biology from the University ofKiev in 1921. Before his graduation, he was hired as an
instructor in zoology at the Polytechnic Institute in Kiev. He
taught there until 1924, when he became an assistant to Yuri
Filipchenko, head of the new Department of Genetics at the
University of Leningrad. Filipchenko was familiar with Morgan's work in the United States and had started a Drosophila
laboratory, where Dobzhansky was encouraged to investigate
the pleiotropic effects of genes.
In 1927 Dobzhansky obtained a fellowship from theInternational Education Board (Rockefeller Foundation)
and arrived in New York on December 27 in order to workwith Thomas Hunt Morgan at Columbia University. In thesummer of 1928 he followed Morgan to the California
Institute of Technology, where Dobzhansky was appointed
assistant professor of genetics in 1929, and professor ofgenetics in 1936. Dobzhansky returned to New York in 1940
as professor of zoology at Columbia University, where heremained until 1962, when he became professor at theRockefeller Institute (renamed Rockefeller University in1965), also in New York City. On July 1, 1970, Dobzhansky
became emeritus at Rockefeller University; in September
1971 he moved to the Department of Genetics at the
University of California, Davis, where he was adjunct professor until his death in 1975.
On August 8, 1924, Dobzhansky married Natalia (Natasha) Sivertzev, a geneticist in her own right, who was working
at the time with the famous Russian biologist I. I. Schmalhausen in Kiev. Natasha was Dobzhansky's faithful companion and occasional scientific collaborator until her death bycoronary thrombosis on February 22, 1969. The Dobzhansky's had only one child, Sophie, who is married toMichael D. Coe, professor of anthropology at Yale University.

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165

In a routine medical check-up on June 1, 1968, it was
discovered that Dobzhansky suffered from chronic lymphatic leukemia, the least malignant form of leukemia. He wasgiven a prognosis of "a few months to a few years" of life
expectancy. Over the following seven years, the progress of
the leukemia was unexpectedly slow and, even more surprising to his physicians, it had little if any noticeable effect on
his energy and work habits. The disease took a conspicuous
turn for the worse in the summer of 1975. In mid-November
Dobzhansky started to receive chemotherapy, but continued
living at home and working at the laboratory. He wasconvinced that the end of his life was near and dreaded thathe might become unable to work and to care for himself.
Mercifully, this never came to pass. He died of heart failureon the morning of December 18, 1975, in my car as I wasrushing him to the hospital. The previous day Dobzhansky
had been, as usual, working in the laboratory.
THE MODERN SYNTHESIS OF EVOLUTIONARY THEORY

Theodosius Dobzhansky was one of the most influential
biologists of the twentieth century; he also was one of themost prolific. His first publication appeared in 1918 when
Dobzhansky was eighteen years old. The complete list of his
publications comprises nearly 600 titles, including a dozen
books. The gamut of subject matter is enormous, andincludes results of experimental research in various biological disciplines, works of synthesis and theory, and essays onhumanism and philosophy, to name but three. The incredibly numerous and diversified published works of Dobzhansky are nevertheless unified—biological evolution is thetheme that threads them together. The place of biologicalevolution in human thought was, according to Dobzhansky,
best expressed in a passage that he often quoted from Pierre
Teilhard de Chardin: "[Evolution] is a general postulate to166

BIOGRAPHICAL MEMOIRS

which all theories, all hypotheses, all systems must hence
forward bow and which they must satisfy in order to be
thinkable and true. Evolution is a light which illuminates all
facts, a trajectory which all lines of thought must follow—thisis what evolution is."Dobzhansky's most significant contribution to science
doubtless was his role in formulating the modern synthesis ofevolutionary theory. His Genetics and the Origin of Species, firstpublished in 1937, may be considered the most importantbook of evolutionary theory in the twentieth century. The
title of the book suggests its theme: the role of genetics in
explaining the origin of species; a synthesis of genetic
knowledge and Darwin's theory of evolution by natural
selection. Considerably revised editions of this book were
published in 1941 and 1951. Genetics of the Evolutionary

Process, published in 1970, was considered by Dobzhansky as
the fourth edition of the earlier book, except that it hadchanged too much to appear under the same title.
By the early 1930s the work of R. A. Fisher, S. Wright,
and J. B. S. Haldane had provided a theoretical framework
accounting for the process of evolution, particularly natural
selection, in genetic terms. This work had a limited impact
on the biology of the time for various reasons: it wasformulated for the most part in mathematical language; it
was almost exclusively theoretical with little empirical corroboration; and it was limited in scope. In Genetics and theOrigin of Species, Dobzhansky completed the integration of
Darwinism and Mendelism in two ways. First, he gathered
the empirical evidence that corroborated the mathematicotheoretical framework. Second, he extended the integrationof genetics with Darwinism much beyond the range of issues
treated by the mathematicians, and into critical evolutionary
issues—such as the process of speciation—not easily subject

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to mathematical treatment. Moreover, Dobzhansky's bookwas written in prose understandable to all biologists.
T h e line of thought of Genetics and the Origin of Species issurprisingly modern—in part, no doubt, because that bookestablished the pattern that successive evolutionary treatises
would largely follow. The book starts with a consideration oforganic diversity and discontinuity. Successively, it deals with
mutation as the origin of hereditary variation, the role ofchromosomal rearrangements, variation in natural populations, natural selection, the origin of species by polyploidy,
the origin of species through gradual development of reproductive isolation, physiological and genetic differences between species, and the concept of species as natural units.
Genetics and the Origin of Species was received with great

excitement by the biological community of the time. The
book would inspire other biologists to bring into the modern
synthesis of evolutionary theory the contributions of suchfields as systematics (E. Mayr, 1942), paleontology (G. G.
Simpson, 1944), and botany (G. L. Stebbins, 1950). Equallyor more important, Genetics and the Origin of Species provided

a conceptual framework that would stimulate experimental
research for many years.
HUMAN EVOLUTION, HUMAN INDIVIDUALITY,
AND THE CONCEPT OF RACE

Dobzhansky extended the synthesis of Mendelism andDarwinism to the understanding of human nature in Mankind Evolving (1962), a book that some think to be asimportant as Genetics and the Origin of Species.

Mankind Evolving remains an unsurpassed synthesis ofgenetics, evolutionary theory, anthropology, and sociology.
Dobzhansky expounded that human nature has two dimensions: the biological, which mankind shares with the rest of

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BIOGRAPHICAL MEMOIRS

life, and the cultural, which is exclusive to man. These twodimensions result from two interconnected processes, biological evolution and cultural evolution:
The thesis to be set forth in the present book is that man has both anature and a "history." Human evolution has two components, thebiological or organic, and the cultural or superorganic. These components
are neither mutually exclusive nor independent, but interrelated andinterdependent. Human evolution cannot be understood as a purely
biological process, nor can it be adequately described as a history ofculture. It is the interaction of biology and culture. There exists a feedback
between biological and cultural processes [Mankind Evolving, p. 18].

Two principal topics of Mankind Evolving are the interrelated concepts of human diversity and race. Dobzhansky's
first major publication on these topics was Heredity, Race, andSociety (1946), a book coauthored with L. C. Dunn, which wastranslated into many languages and sold more than one
million copies. The two topics are the main subject of Genetic
Diversity and Human Equality (1973), the last of Dobzhansky's
books published before his death. (Dobzhansky left his
manuscript completed for another book, Evolution, coauthored with F. J. Ayala, G. L. Stebbins, and J. W. Valentine,
which appeared in 1977.)
Dobzhansky set forth that the individual is not theembodiment of some ideal type or norm, but rather a uniqueand unrepeatable realization in the field of quasi-infinite
possible genetic combinations. The pervasiveness of genetic
variation provides the biological foundation of human individuality and leads to demystification of the much abusedconcept of race. Dobzhansky emphasized that populations orgroups of populations differ from each other in the frequencies of some genes. These differences may be recognized by
distinguishing populations of a given species as races. The
number of races and the boundaries between them arelargely arbitrary, because rarely if ever are populations of

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169

the same species separated by sharp discontinuities in their
genetic makeup. Most important is the fact that races arepolymorphic for the same genetic variants that may be used
to distinguish one race from another. There is more genetic
variation within any human race than there are genetic
differences between races. It follows, as Dobzhansky saw it,that individuals should be evaluated by what they are, not by
the race to which they belong.
Dobzhansky considered human diversity a fact belonging
to the realm of observable natural phenomena: "People are
innately, genetically, and therefore irremediably diverse andunlike" (Genetic Diversity and Human Equality, p. 4). Biologicaldistinctiveness is not, however, a basis for inequality. Equality—as in equality in law and equality of opportunity—"pertains to the rights and the sacredness of life of every
human being" (loc. cit.). Dobzhansky pointed out that equality in law and equality of opportunity are the best strategy tomaximize the benefits of human biological diversity. "Denialof equality of opportunity stultifies the genetic diversity withwhich mankind became equipped in the course of its evolutionary development. Inequality conceals and stifles somepeople's abilities and dissembles the lack of abilities in others.
Conversely equality permits an optimal utilization of thewealth of the gene pool of the human species" (Mankind
Evolving, p. 285). Dobzhansky had little patience with racial
prejudice or social injustice, and castigated those who pretended to base them on what he called "bogus 'science' ofrace prejudice."
Dobzhansky's lasting interest in the relevance of biology,
and particularly evolutionary theory, to human affairs isevident in scores of articles that he wrote on the subject andin the titles of some of his books: Heredity, Race, and Society(1946), Evolution, Genetics, and Man (1955), The Biological
Basis of Human Freedom (1956), Radiation, Genes, and Man

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BIOGRAPHICAL MEMOIRS(1959, with B. Wallace), Mankind Evolving (1962), Heredity
and the Nature of Man (1964), The Biology of Ultimate Concern(1967), and Genetic Diversity and Human Equality (1973).
EXPERIMENTAL POPULATION GENETICS

Dobzhansky was not only a great theorist of evolution, healso was an eminent and extremely productive experimentalist. During half a century of intensive research and publication, he made fundamental empirical contributions to virtually every major problem of population genetics.
Dobzhansky's first contribution to population genetics
appeared in 1924—an investigation of local and geographic
variation in the color and spot pattern of two Coccinellidae
genera, Harmonia and Adalia. These ladybird beetles exhibit
local polymorphisms, which in some species vary from one toanother locality. Dobzhansky explained the genetic variation
within and between populations as results of the same
fundamental evolutionary processes. Some cardinal themesof Dobzhansky's evolutionary theory are already present inthis work: the pervasiveness of genetic variation, geographic
variation as an extension of local polymorphism, and as thefirst but reversible step toward species differentiation. Dobzhansky continued the study of natural populations of ladybird beetles until the time he left Russia in 1928, and on
occasion returned thereafter to them (for example, the 94page monograph published in 1941).
The beginning of Dobzhansky's studies on the population
genetics of Drosophila can be traced to 1933, when hepublished a paper on the sterility of hybrids between D.
pseudoobscura and D. persimilis (then known as D. pseudoobscura

races A and B). In a series of papers he investigated thephysiological, developmental, and genetic causes of hybrid
sterility. This work developed from the convergence of two
independent previous lines of investigation, the genetics of

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translocations and the study of sex determination. It led in1935 to a formulation of the concept of (sexually reproducing) species still accepted today: "That stage of the evolutionary process at which the once actually or potentially interbreeding array of forms becomes segregated in two or more
separate arrays which are physiologically incapable of interbreeding." This notion establishes that reproductive isolation
is what sets species apart. It is also an evolutionary definition
that sees speciation as a dynamic process of gradual change.
Dobzhansky introduced in 1935, and formally proposed in1937 (American Naturalist, 71:404-20), the term "isolating
mechanisms" to designate the phenomena that impede geneexchange between species. He identified, classified, andthroughout his life investigated the various kinds of isolating
mechanisms. "Isolating mechanisms" is one example of themany useful terms coined by Dobzhansky that have become
part of the standard terminology of evolutionary biology.
The experimental contributions of Dobzhansky to population genetics are so numerous, and so diversified, as to defy
the possibility of a brief summary. I shall mention a few
principal areas of research and list the years in which hepublished some of the major papers in each subject.
His classical studies on the geographical and temporalvariation of chromosomal arrangements in Drosophila pseudoobscura and its relatives started with a publication in 1936;
in 1938 he published a paper on altitudinal variation; in1943 a paper on seasonal variation, followed in 1946 by alaboratory study (in collaboration with Sewall Wright) showing adaptive differences (with respect to temperature) between chromosomal arrangements. Numerous other publications on this subject appeared through the 1930s and1940s, and would continue throughout Dobzhansky's life.
Starting in the 1950s the study of geographical variation inchromosomal arrangements was extended to the D. willistoni

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BIOGRAPHICAL MEMOIRSgroup of tropical species, which exhibit even greater degrees
of local polymorphism and geographical variation than D.
pseudoobscura.

Dobzhansky, in collaboration with A. H. Sturtevant, realized that the evolutionary phylogeny of chromosomal arrangements can be reconstructed by deciphering the patterns of overlapping chromosomal inversions found innatural populations of Drosophila; the first phylogeny was
published in 1936. This technique became a major tool in thereconstruction of evolutionary history and was applied tomany species by Dobzhansky and others. A notable exampleof the success of this method is the reconstruction of thephylogeny of Hawaiian species by H. L. Carson and hiscolleagues.
Originally Dobzhansky thought that the various chromosomal arrangements of D. pseudoobscura were adaptively
equivalent (see the 1941 edition of Genetics and the Origin ofSpecies), and hence that their geographical and temporalvariation was the result of genetic drift. Eventually hebecame convinced that the chromosomal polymorphisms are
adaptive, but remained interested in the roles that migration,
mutation, and drift play in the maintenance of variation innatural populations. Estimates of rates of mutation andaccumulation of lethals were first published in 1941 (again in
collaboration with Sewall Wright); estimates of the criticalparameter Nm (the product of effective population size times
migration rate) in natural populations appeared in 1942,
1952, and 1954. He developed techniques for the experimental study of migration in nature and published pioneering works in the 1940s; he would return later to this researchand did spend most of the last few summers of his life at the
beloved cabin in Mather, near Yosemite in Sierra Nevada,measuring the rates of dispersion in Drosophila.

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Dobzhansky realized early the need to investigate theecological basis of natural variation. He investigated thenutritional preferences first of D. pseudoobscura and later ofother species (papers in the 1950s). Several papers (late1950s) were devoted to ascertaining—particularly in D. willistoni—the relationships between the ecological diversity ofthe environment and the degree of genetic polymorphism.
He also investigated the physiological basis of adaptation,
starting with studies of fecundity and rates of oxygen consumption published in 1935.
Genetic variation is a necessary condition for evolution.
Dobzhansky probably dedicated more research effort to thestudy of genetic variation in natural populations than to any
other single problem. He studied morphological variations,but saw that physiological variation—i.e., variation affecting
fitness—would be most important in evolution. Taking advantage of genetic methods to produce flies homozygous forfull chromosomes, he first investigated the frequency oflethal mutations in nature. In 1942 he published a classicalpaper showing that variation in fitness is a pervasive phenomenon: virtually every chromosome found in nature
carries genes that are deleterious in homozygous condition;
most individuals in nature are well adapted because they areheterozygous for the deleterious variants. "It is the adaptive
level of individuals heterozygous for various chromosomes
which is most important" {Genetics, 27[1942]:487). Dobzhansky pursued the study of this "concealed variation"affecting fitness for two and a half decades. When thetechniques of gel electrophoresis were first applied to population genetics in the mid-1960s, he became quite enthusiastic. He appreciated that these studies made it possible toobtain quantitative measures of genetic variation. He also
saw that there is a trade-off between electrophoretic studies

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BIOGRAPHICAL MEMOIRS

and the former methods of studying concealed variation: theadaptive role of electrophoretic variation is not immediately
apparent.
In the 1940s Dobzhansky started work with the D. willistoni group of species that would result in contributions toevolutionary genetics comparable in significance to thosederived from the study of D. pseudoobscura and its relatives.
The most unique results with this group concern the processof speciation and concommitant development of reproductive isolation. The willistoni group contains several sibling
species. One of these, D. paulistorum, is a cluster of semispecies, or species in statu nascendi, where varying degrees ofhybrid sterility, and particularly sexual isolation, can beobserved. He discovered and took advantage of this favorable state of affairs for the experimental study of a fundamental evolutionary problem—speciation. He also used D.
paulistorum as the organism for the laboratory study of sexualisolation by selection. This work brought about some unsought publicity in such journals as The New York Times andTime magazine.
From around 1960 until the time of his death, Dobzhansky worked on the geotactic and phototactic behavior of
Drosophila. His interest in this work encompassed the determination of the genetic basis of some simple behavioral
traits, but his main interest was to model the interaction
among selection, gene flow, and population size for a behavioral trait with low heritability. There were some unexpected
but instructive results, such as the observation of what prima
facie appeared as a case of negative heritability.
CONTRIBUTIONS TO GENERAL GENETICSAND OTHER EXPERIMENTAL WORK

Dobzhansky made significant contributions to other areasof population biology, particularly ecology and systematics,

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in addition to his work in population genetics. As pointed out
above, much of Dobzhansky's population genetics research
had an ecological component: geographical and temporalvariation in population characteristics, food resource preferences of Drosophila species, rates of dispersion, ecologicaldiversity of environments, and so on. Among his other
ecological investigations, two at least deserve mention. One is
the study of species' diversity in tropical forests, which led
him to a hypothesis to account for the high level of species
diversification in the tropics (1950). Then, in the earlysixties, he published several papers on the estimation of the
innate capacity for increase in numbers in diverse Drosophila
populations.
Dobzhansky also made significant contributions to "classical" genetics, particularly during the 1920s and 1930s. I shallmention but a few. Using translocations between the second
and third chromosomes of Drosophila melanogaster, Dobzhansky demonstrated that the linear arrangement of genes
based on linkage relationships corresponds to a linear arrangement of genes in chromosomes (1929). This linear
correspondence had been postulated before, but proof was
first provided by Dobzhansky (and independently by Muller
and Painter in the same year). Also in 1929, Dobzhansky
advanced the first sophisticated cytological map of a chromosome—chromosome III of D. melanogaster. He showed thatthe relative distances between genes are different in thelinkage and in the cytological map; genes clustered aroundthe center of the linkage map are spread throughout a larger
portion of the cytological map. He correctly inferred that thefrequency of crossing over is not evenly distributed throughout the chromosome. Later he produced cytological maps ofthe chromosomes II (1930) and X (1932) of D. melanogaster,and propounded that the centromere (the "spindle fiber
attachment" in the terminology of the time) is a permanent

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feature of chromosomes. He demonstrated that translocations decrease the frequency of crossing over and advanced ahypothesis to account for this reduction (1931).
Dobzhansky demonstrated that the determination of femaleness by the X chromosome is not the result of a single ora small group of genes, but to multiple factors distributed
throughout the chromosome (1931). His publications on thegenetic and environmental factors affecting sex determination started in 1928 and continued for more than a decade.
These studies included work on bobbed mutants in the Y
chromosome and their role in male sterility (1933), as well as
numerous publications on gynandromorphs and "superfemales." His publications concerning developmental genetics started in 1930 and continued for many years.
Working with D. melanogaster in the laboratory headed by
Y. F. Filipchenko at the University of Leningrad, he madethe first systematic investigation of the pleiotropic, or manifold, effects of genes (1927), a phenomenon that held his
interest for many years (e.g., Genetics, 28[1943]:295-303).
Dobzhansky's contributions to the study of position effects
started in 1932 and continued for several years (a review
appeared in 1936).
HUMANISM

Dobzhansky's interest in the interface between biology
and human problems was expressed in numerous publications that flowed as a continuous stream from the mid-1940s
onward. Dobzhansky's concern was probably kindled byseveral convergent influences. One factor was the racial
bigotry in Europe that contributed to the triggering ofWorld War II; another, Lysenko's suppression of genetics
and geneticists in the USSR; a third, his association as acolleague and intimate friend with L. C. Dunn, whose

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compassion for the human predicament was much revered
by Dobzhansky, and who became greatly involved in providing shelter in the United States for scientists fleeing from
Nazi persecution. Doubtless there was also Dobzhansky's
own personal and intellectual maturation that made him
willing to tackle social and socio-political questions.
As pointed out above, Dobzhansky published with L. C.
Dunn Heredity, Race, and Society in 1946, and continued

publishing on race questions from a biological perspective
until the end of his life. Publications criticizing eugenic
movements appeared in 1952 and 1964; the subject ofeugenics was treated in other papers and several books. In
1946 he translated into English T. D. Lysenko's Heredity and
Its Variability as a way to expose Lysenko's quackery. Dobzhansky criticized Lysenko's "science," and particularly Lysenko's eradication of genetics and geneticists, in several
articles published between 1946 and 1958.
Dobzhansky was concerned with the role of religion inhuman life, and he explored the evolutionary basis ofreligion in several articles in the 1960s and 1970s, as well asin The Biology of Ultimate Concern (1967). Yet he did nothesitate to criticize (1953) the antievolutionist stand of Pope
Pius XII in the encyclical Humani Generis, or that of fundamentalist Protestants (1973).
Dobzhansky often expressed his frustration at the limited
influence of biology on the thinking of philosophers. He sawthat evolutionary biology raises new philosophical problems
and throws light on old ones. He wrote several essays on
philosophical questions, such as the concepts of determinism
and chance (1963, 1966, 1974), transcendent phenomena(1965, 1967), organismic, or compositionist, approaches in
the philosophy of biology (1967, 1968), and the "creative"
character of biological evolution (1954, 1967, 1974).

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BIOGRAPHICAL MEMOIRSPERSONAL TRAITS

Dobzhansky was excellent in the classroom, and a truly
distinguished educator of scientists. Throughout his academic career Dobzhansky had more than thirty graduate
students, and an even greater number of postdoctoral andvisiting associates, many of them from foreign countries.
Some distinguished geneticists and evolutionists in the United States and abroad are his former students. Dobzhansky
spent long periods of time in foreign academic institutions,and was largely responsible for the establishment or development of genetics and evolutionary biology in various countries, notably Brazil, Chile, and Egypt.
Dobzhansky gave generously of his time to other scientists, particularly to young ones and to students. On the other
hand, he resented time spent in committee activities, which
he shunned as much as he reasonably could. Throughout hisacademic career, Dobzhansky avoided administrative posts;
he alleged, perhaps correctly, that he had neither temperament nor ability for management. Most certainly, he preferred to dedicate his working time to research and writing
rather than to administration.
Dobzhansky was a world traveler and an accomplishedlinguist, able to speak fluently six languages and to readseveral more. He was a good naturalist, and never lacked
time for a hike, whether in the California Sierras, the New
England forests, or the Amazonian jungles. He loved horseback riding but practiced no other sports. Dobzhansky's
interests covered a broad spectrum of human activities,
including the plastic arts, music, history, Russian literature,
cultural anthropology, philosophy, religion, and, of course,
science. His artistic preferences were unsystematic and definitely traditional. His favorite composer was Beethoven,followed by Bach and other baroques; he loved Italian
operas, but had little appreciation for most twentieth century

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music and a definite distaste for atonalism. In painting,
Dobzhansky admired the Italian Renaissance as well as the
Dutch and Spanish painters of the seventeenth century; heappreciated the French Impressionists but detested cubism
and all subsequent styles and schools.
Dobzhansky's most obvious personality traits were, perhaps, magnanimity and expansiveness. He recognized andgenerously praised the achievements of other scientists; headmired the intellect of his colleagues, even when admiration was alloyed with disagreement. He made many longlasting friendships, usually started by professional interactions. Many of Dobzhansky's friends were scientists
younger than himself, who either had worked in his laboratory as students, postdoctorals, or visitors or had met him
during his trips. He was conspicuously affectionate and loyal
toward his friends; he expected affection and loyalty inreturn. Dobzhansky's exuberant personality was manifest
not only in his friendships but also in his antipathies, which
he was neither able nor often willing to hide.
Dobzhansky was a religious man, although he apparently
rejected fundamental beliefs of traditional religion, such as
the existence of a personal God and of life beyond physicaldeath. His religiosity was grounded on the conviction that
there is meaning in the universe. He saw that meaning in thefact that evolution has produced the stupendous diversity of
the living world and has progressed from primitive forms oflife to mankind. Dobzhansky held that, in man, biologicalevolution has transcended itself into the realm of selfawareness and culture. He believed that somehow mankind
would eventually evolve into higher levels of harmony andcreativity.
Dobzhansky's prodigious scientific productivity was madepossible by incredible energy and very disciplined work
habits. His enormous success as the creator of new ideas and180

BIOGRAPHICAL MEMOIRS

as a synthesizer was, at least in part, based on his broad
knowledge, his phenomenal memory, and an incisive mind
able to see the relevance that a new discovery or a new theory
might have with respect to other theories or problems. His
success as an experimentalist depended on a wise blending offield and laboratory research; whenever possible he combined both in the study of a problem, using laboratory
studies in order to ascertain or to confirm the causal processes involved in the phenomena discovered in nature. He
obtained the collaboration of mathematicians in order todesign theoretical models for experimental testing and toanalyze statistically his empirical observations. He was no
inventor or gadgeteer, but he had an uncanny ability to
exploit the possibilities of any suitable experimental apparatus or experimental method.
Dobzhansky selected organisms that provided the bestmaterials to investigate the problems that interested him: thebiological particularities of D. pseudoobscura and its relatives
and of the D. willistoni group made possible many of Dobzhansky's discoveries. He always worked at the utmost levelof genetic resolution possible at any given time: he took
advantage of the early methods of genetic analysis, then ofvarious cytological tools, later of the giant polytene chromosomes, and of the techniques to produce chromosomal
homozygotes. When gel electrophoresis came about, he
immediately recognized its enormous potential as a tool tostudy population genetics problems; he felt that it was toolate in his life for him to learn the technique but encouraged
his students and collaborators to use it and collaborated inseveral projects using it.

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RECOGNITION AND AWARDS

Dobzhansky was elected to the National Academy of
Sciences in 1943. He was also elected to the American
Academy of Arts and Sciences, the American PhilosophicalSociety, and many foreign academies, including the Royal
Society of London, The Royal Swedish Academy of Sciences,
The Royal Danish Academy of Sciences, The Brazilian
Academy of Sciences, the Academia Leopoldina, and theAcademia Nazionale dei Lincei.
He was president of the Genetics Society of America(1941), the American Society of Naturalists (1950), theSociety for the Study of Evolution (1951), the American
Society of Zoologists (1963), the American Teilhard de
Chardin Association (1969), and the Behavior Genetics Association (1973).
Dobzhansky received more than twenty honorary degrees from institutions that include the Universities of Sao
Paulo in Brazil (1943), Miinster in Germany (1958), Montreal in Canada (1958), Sydney in Australia (1960), Oxford in
England (1964), Louvain in Belgium (1965), Padua in Italy(1968), and in the United States, Chicago (1959), Columbia(1964), Michigan (1966), Syracuse (1967), Berkeley (1968),
and Northwestern (1968).
He received the Daniel Giraud Elliot Medal (1946) andthe Kimber Genetics Award (1958) from the National Academy of Sciences, the Darwin Medal from the Academia
Leopoldina (1959), the Anisfield-Wolf Award (1963), thePierre Lecomte du Nouy Award (1963), the Addison Emery
Verrill Medal from Yale University (1966), the Gold Medal
Award for Distinguished Achievement in Science from theAmerican Museum of Natural History (1969), and the Benjamin Franklin Medal from the Franklin Institute (1973). In
1964 he received the National Medal of Science from President Lyndon Johnson.

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With C. B. Bridges. The Mutant "Proboscipedia" in Drosophilamelanogaster—a case of hereditary homoosis. Z. Wiss. Biol.
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With N. P. Sivertzev-Dobzhansky. Deficiency and duplication for
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With J. Schultz. The distribution of sex-factors in the X-chromosome oi Drosophila melanogaster. J. Genet., 28:349—86.

With J. Schultz. The relation of a dominant eye color in Drosophilamelanogaster to the associated chromosome rearrangement. Genetics, 19:344-64.
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188

BIOGRAPHICAL MEMOIRSWith C. C. Tan. Studies on hybrid sterility. III. A comparison of
the gene arrangement in two species, Drosophila pseudoobscuraand Drosophila miranda. Z. Indukt. Abstamm. Vererbungsl.,
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With A. H. Sturtevant. Inversions in the third chromosome of wildraces of Drosophila pseudoobscura, and their use in the study ofthe history of the species. Proc. Natl. Acad. Sci. USA, 22:44850.
With A. H. Sturtevant. Geographical distribution and cytology of"sex-ratio" in Drosophila pseudoobscura and related species. Genetics, 21:473-90.
Observations on the species related to Drosophila affinis, withdescriptions of seven new forms. Am. Nat., 70:174—84.
1937
Genetics and the Origin of Species. New York: Columbia University

Press, xvi + 364 pp. (2d rev. ed., xvii, 446 pp., 1941; 3d ed., x +364 pp., 1951; Japanese trans., Tokyo, 1953; Spanish trans.,
Madrid, 1955.)
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1938
With M. L. Queal. Genetics of natural populations. I. Chromosome
variation in populations of Drosophila pseudoobscura inhabiting
isolated mountain ranges. Genetics, 23:239-51.
With M. L. Queal. Genetics of natural populations. II. Genie
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With M. M. Rhoades. A possible method for locating favorable
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1939
Genetics of natural populations. IV. Mexican and Guatemalan
populations of Drosophila pseudoobscura. Genetics, 24:390—412.
Fatti e problemi della condizione "rapporto-sessi" (sex-ratio) in
Drosophila. Sci. Genet., 1:67-75.
Microgeographic variation in Drosophila pseudoobscura. Proc. Natl.
Acad. Sci. USA, 24:311-14.
Experimental studies on genetics of free-living populations ofDrosophila. Biol. Rev., 14:339-86.
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With D. Sokolov. Structure and variation of the chromosomes in
Drosophila azteca. J. Hered., 30:3-19.
With R. Mather. Morphological differences between the "races" ofDrosophila pseudoobscura. Am. Nat., 73:5—25.
1940
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1941
Discovery of a predicted gene arrangement in Drosophila azteca.
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The race concept in biology. Sci. Mon. 52:161—65.
Chromosomal differences between races and species of Drosophila(University of Pennsylvania Bicentennial Conference). In: Cytology, Genetics and Evolution, pp. 47—57. Philadelphia: Universityof Pennsylvania Press.
On the genetic structure of natural populations of Drosophila. In:
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With S. Wright. Genetics of natural populations. V. Relations
between mutation rate and accumulation of lethals in populations of Drosophila pseudoobscura. Genetics, 26:23—51.
With B. Spassky. Intersexes in Drosophila pseudoobscura. Proc. Natl.
Acad. Sci. USA, 27:556-62.

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Beetles of the genus Hyperaspis inhabiting the United States.
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1942
Races and methods of their study. Trans. N. Y. Acad. Sci., 2:115—
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Biological Symposia, vol. 6 (editor), xii + 355 pp. Pennsylvania: The
Jaques Cattell Press.
Biological adaptation. Sci. Moti., 55:391-402.
With C. Epling. Genetics of natural populations. VI. Microgeographic races in Linanthus parryae. Genetics, 27:317—32.
With S. Wright and W. Hovanitz. Genetics of natural populations.
VII. The allelism of lethals in the third chromosome of Drosophila pseudoobscura. Genetics, 27:363—94.
With A. M. Holz and B. Spassky. Genetics of natural populations.
VII. Concealed variability in the second and fourth chromosomes of Drosophila pseudoobscura and its bearing on the problemof heterosis. Genetics, 27:464-90.
With C. D. Darlington. Temperature and "sex-ratio" in Drosophila
pseudoobscura. Proc. Natl. Acad. Sci. USA, 28:45-48.
Darwin and our intellectual heritage. Science, 95:303-4.
1943
Genetics of natural populations. IX. Temporal changes in thecomposition of populations of Drosophila pseudoobscura. Genetics, 28:162-86.
Genetics and human affairs. Teach. Biol., 12:97-106.
O gen como unidade auto-reproductora da fisiologia celular. Rev.
Agric, 18:387-96.
Heterosis. Rev. Agric, 18:397-98.
The species concept. Rev. Agric, 18:441-42.
With A. Dreyfus. Chromosomal aberrations in Brazilian Drosophila
ananassae. Proc. Natl. Acad. Sci. USA, 29:301-5.
With A. M. Holz. A re-examination of the problem of manifold
effects of genes in Drosophila tnelanogaster. Genetics, 28:295—
303.
With C. Pavan. Chromosome complements of some south-Brazilian species of Drosophila. Proc. Natl. Acad. Sci. USA, 29:368-75.
With C. Pavan. Studies on Brazilian species of Drosophila. Bol. Fac.
Filos. Cienc. Let. Univ. Sao Paulo (Biol. Geral), 36:7-72.

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With S. Wright. Genetics of natural populations. X. Dispersion
rates in Drosophila pseudoobscura. Genetics, 28:304-40.
1944
Distribution of heterochromatin in the chromosomes of Drosophila
pallidipennis. Am. Nat., 78:198-213.
Rules of geographic variation. Science, 99:127-28.
Chromosomal races in Drosophila pseudoobscura and Drosophila persi-

milis. Carnegie Inst. Washington Publ. no. 554:47—144.
On species and races of living and fossil man. Am. J. Phys.
Anthropol., 2:251-65.
With E. Mayr. Experiments on sexual isolation in Drosophila. I.
Geographic strains of Drosophila willistoni. Proc. Natl. Acad. Sci.
USA, 30:238-44.
With G. Streisinger. Experiments on sexual isolation in Drosophila.
II. Geographic strains of Drosophila prosaltans. Proc. Natl. Acad.
Sci. USA, 30:340-45.
With B. Spassky. Genetics of natural populations. XI. Manifestation of genetic variants in Drosophila pseudoobscura in different
environments. Genetics, 29:270-90.
Experiments on sexual isolation in Drosophila. III. Geographic
strains of Drosophila sturtevanti. Proc. Natl. Acad. Sci. USA,
30:335-39.
With C. Epling. Taxonomy, geographic distribution, and ecology
of Drosophila pseudoobscura and its relatives. Carnegie Inst.
Washington Publ. no. 554:1-46.
1945
Directly observable genetic changes in populations of Drosophila
pseudoobscura. Biom. Bull., 1:7—8.
With E. Mayr. Experiments on sexual isolation in Drosophila. IV.
Modification of the degree of isolation between Drosophila
pseudoobscura and Drosophila persimilis and of sexual preferencesin Drosophila prosaltans. Proc. Natl. Acad. Sci. USA, 31:75—82.
With H. Levene. Experiments on sexual isolation in Drosophila. V.
The effect of varying proportions of Drosophila pseudoobscuraand Drosophila persimilis on the frequency of insemination in
mixed populations. Proc. Natl. Acad. Sci. USA, 31:274-81.
With J. T. Patterson. Incipient reproductive isolation between two
subspecies of Drosophila pallidipennis. Genetics, 30:429—38.

192

BIOGRAPHICAL MEMOIRSAn outline of politico-genetics. Science, 102:234-36.
1946
With S. Wright. Genetics of natural populations. XII. Experimental reproduction of some of the changes caused by natural
selection in certain populations of Drosophila pseudoobscura.
Genetics, 31:125-56.
Complete reproductive isolation between two morphologically similar species of Drosophila. Ecology, 27:205-11.
Trofim Denisovich Lysenko, Heredity and Its Variability, trans. Th.
Dobzhansky. 65 pp. New York: King's Crown Press.
With L. C. Dunn. Heredity, Race, and Society. 115 pp. New York:
Penguin Books. (2d ed. 1952, New York: The New American
Library. 3d ed., 1956, New York: Mentor Books. Trans.:
Portuguese, 1952; Arabic, 1956; Swedish, 1956; French, 1964;
Norwegian, 1965.)
With B. Wallace. Experiments on sexual isolation in Drosophila.
VIII. Influence of light on the mating behavior of Drosophila
subobscura,

Drosophila

persimilis,a n d Drosophila

pseudoobscura.

Proc. Natl. Acad. Sci. USA, 32:226-34.
Genetics of natural populations. XIII. Recombination and variability in populations of Drosophila pseudoobscura. Genetics, 31:269—
90.
Lysenko's "genetics." J. Hered., 37:5-9.
The new genetics in the Soviet Union. Am. Nat., 80:649-51.
1947
Adaptive changes induced by natural selection in wild populationsof Drosophila. Evolution, 1:1—16.
Effectiveness of intraspecific and interspecific matings in Drosophila
pseudoobscura and Drosophila persimilis. Am. Nat., 81:66—72.

A directional change in the genetic constitution of a natural
population of Drosophila pseudoobscura. Heredity, 1:53-64.
N. I. Vavilov, a martyr of genetics. J. Hered., 38:226-32.
With M. F. Ashley Montagu. Natural selection and the mental
capacities of mankind. Science, 105:587-90.
With B. Spassky. Evolutionary changes in laboratory cultures ofDrosophila pseudoobscura. Evolution, 1:191—216.

Genetics of natural populations. XIV. A response of certain gene

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arrangements in the third chromosome of Drosophila pseudoobscura to natural selection. Genetics, 32:142-60.
With S. Wright. Genetics of natural populations. XV. Rate ofdiffusion of a mutant gene through a population of Drosophila
pseudoobscura. Genetics, 32:303-24.
1948
Genetics of natural populations. XVI. Altitudinal and seasonalchanges produced by natural selection in certain populations ofDrosophila pseudoobscura and Drosophila persimilis. Genetics,

33:158-76.
Chromosomal variation in populations of Drosophila pseudoobscura
which inhabit northern Mexico. Am. Nat., 82:97-106.
With H. Levene. Genetics of natural populations. XVII. Proof ofoperation of natural selection in wild populations of Drosophila
pseudoobscura. Genetics, 33:537-47.
Genetics of natural populations. XVIII. Experiments on chromosomes of Drosophila pseudoobscura from different geographic
regions. Genetics, 33:588-602.
With C. Epling. The suppression of crossing over in inversion
heterozygotes of Drosophila pseudoobscura. Proc. Natl. Acad. Sci.
USA, 34:137-41.
1949
Observations and experiments on natural selection in Drosophila.
Proc. Eighth Int. Cong. Genetics, pp. 210-24. Lund: Berlingska
Boktryckeriet.
The suppression of a science. Bull. At. Sci., 5:144-46.
On some of the problems of population genetics and evolution.
Ric. Sci. Suppl., 19:11-17.
Review and perspectives of the Symposium on Ecological andGenetic Factors of Speciation and Evolution. Ric. Sci. Suppl.,
19:128-34.
Conceitos fundamentals de genetica. Agronomia (Rio de Janeiro),
8:253-58, 341-57.
Foreword. In: Factors of Evolution, ed. I. Schumalhausen, trans. I.
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505 pp. New York: McGraw-Hill. (5th ed., 1958, xiv 4- 459 pp.
Spanish trans., 1961; Italian trans., 1965.)
With H. Burla, A. B. daCunha, A. R. Cordeiro, Ch. Malogolowkin,
and C. Pavan. The willistoni group of sibling species of Drosophila. Evolution, 3:300-14.
Marxist biology, French style. J. Hered., 40:78—79.
1950
The genetic basis of evolution. Sci. Am., 182:32-41.
Heredity, environment, and evolution. Science, 11:161—66.
Evolution in the tropics. Am. Sci., 38:209-21.
Nature and origins of races. Encyclopedia Americana, vol. 23, pp.
107—11. New York: Americana Corp.
Genetics of natural populations. XIX. Origin of heterosis throughnatural selection in populations of Drosophila pseudoobscura.
Genetics, 35:288-302.
The genetic nature of differences among men. In: Evolutionary
Thought in America, ed. S. Persons. New Haven: Yale University
Press.
The chromosomes of Drosophila willistoni. J. Hered., 41:156—58.
Genetics. Sci. Am., 183:55-58.
Mendelian populations and their evolution. Am. Nat., 84:401—18.
With C. Pavan. Local and seasonal variations in relative frequenciesof species of Drosophila in Brazil. J. Anim. Ecol., 19:1—14.
With H. Burla and A. B. daCunha. A comparative study ofchromosomal polymorphism in sibling species of the willistonigroup of Drosophila. Am. Nat., 84:229-46.
With B. Spassky and S. Zimmering. Comparative genetics ofDrosophila prosaltans. Heredity, 4:189-200.
With B. Spassky. Comparative genetics of Drosophila willistoni.
Heredity, 4:201-15.
With G. Black and C. Pavan. Some attempts to estimate species
diversity and population density of trees in Amazonian forests.
Bot. Gaz., 111:413-524.
With C. Pavan and H. Burla. Diurnal behavior of some neotropical
species of Drosophila. Ecology, 31:36-43.
With A. B. daCunha and H. Burla. Adaptive chromosomal polymorphism in Drosophila willistoni. Evolution, 4:212—35.
With H. Burla, A. B. daCunha, A. G. L. Cavalcanti, and C. Pavan.
Population density and dispersal rates. Ecology, 31:393—404.

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Death of a science in Russia—Heredity, East and West. J. Hist.
Med. Allied Sci., 3:339-42.
1951
Human diversity and adaptation. Symp. Quant. Biol., 15:385—400.
Race and humanity. Science, 113:264—66.
Evolution in process. Sci. Mon., 62:403-4.
Human races in the light of genetics. Int. Soc. Sci. Bull. (UNESCO), 3:660-63.
Experiments on sexual isolation in Drosophila. X. Reproductive
isolation between Drosophila pseudoobscura and Drosophila persimi-

lis under natural and under laboratory conditions. Proc. Natl.
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1953
Natural hybrids of two species of Arctostaphylos in the Yosemite
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Le naufrage de la biologie en Russie. Preuves (Aug.-Sept.): 92-98.
With O. Pavlovsky. Indeterminate outcome of certain experiments
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With J. Murc.a Pires and G. A. Black. An estimate of the number of
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Soviet Marxism and natural science. Science, 133:1762—63.
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Ein Beitrag zur genetischen Basis der Quanten-Evolution. In:
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With B. Wallace. Experimental proof of balanced genetic loads in
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loads in natural populations of Drosophila pseudoobscum. Genetics, 48:361-73.
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"Wild" and "domestic" species of Drosophila. In: The Genetics ofColonizing Species, ed. H. G. Baker and G. L. Stebbins, pp. 533—
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1966
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With I. Asimov. The Genetic Effects of Radiation. Tennessee: U.S.
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An essay on religion, death, and evolutionary adaptation. Zygon,
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Milislav Demerec. Am. Philos. Soc. Year Book, 1966:115-21.
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Evolutionary Biology, ed. Th. Dobzhansky, M. K. Hecht, and W. C.
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With B. Spassky. Responses of various strains of Drosophila pseudoobscura and Drosophila persimilis to light and gravity. Am. Nat.,
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Of flies and men. Am. Psychol., 22:41-48.
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Etude genetique des reactions de Drosophiles a la lumiere et a lapesanteur. Ann. Biol. Clin., 6:483-97.
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With B. Spassky. An experiment on migration and simultaneous
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Human values in an evolutionary world. In: Human Values andAdvancing Technology, ed. C. P. Hall, pp. 49—67. New York:
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1968
With W. W. Anderson, C. Oshima, T. Watanabe, and O. Pavlovsky.
Genetics of natural populations. XXXIX. A test of the possible
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Evolution and behaviour. In: International Encyclopedia of the Social
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Darwin versus Copernicus. In: Changing Perspectives on Man, ed. B.
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With R. Richmond. Chromosomal polymorphism in populations ofDrosophila immigrans on the island of Maui, Hawaii. Univ. Tex.
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Heredity. In: Encyclopaedia Britannica, vol. 11, pp. 419—28. Chicago: Encyclopaedia Britannica.
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BIOGRAPHICAL MEMOIRSWith B. Spassky, R. C. Richmond, S. Perez-Salas, O. Pavlovsky, C.
A. Mourao, A. S. Hunter, H. Hoenigsberg, and F. J. Ayala.
Geography of the sibling species related to Drosophila willistoni,
and of the semispecies of the Drosophila paulistorum complex.
Evolution, 25:129-43.
With O. Pavlovsky. Experimentally created incipient species ofDrosophila. Nature, 230:289-92.
Evolution and man's conception of himself. Teilhard Rev., 5:65—
69.
With J. R. Powell and F. J. Ayala. Polymorphisms in continental
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Darwin versus Copernicus. In: In the Name of Life, ed. B. Landis and
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Teilhard de Chardin and the orientation of evolution. In: Process
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Race equality. In: The Biological and Social Meaning of Race, ed. R. H.

Osborne, pp. 13—24. San Francisco: Freeman.
The unexpected universe. Am. Anthropol., 73:305—6.
1972
Darwinian evolution and the problem of extraterrestrial life.
Perspect. Biol. Med., 15:157-75.
Man's evolutionary future. Sci. Teach., 39:17—20.
Species of Drosophila. Science, 177:664—69.
A review of A. Koestler's The Case of the Midwife Toad. Perspect.
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Genetics and the diversity of behavior. Am. Psychol., 27:523-30.
The ascent of man. Soc. Biol., 19:367-78.
On the evolutionary uniqueness of man. In: Evolutionary Biology,
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415-30. New York: Appleton-Century-Crofts.
With W. W. Anderson and O. Pavlovsky. A natural population of

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Drosophila transferred to a laboratory environment. Heredity,
28:101-7.
A review of William B. Provine's The Origins of Theoretical Population

Genetics. Perspect. Biol. Med., 15:645-46.
Genetics and the races of man. In: Sexual Selection and the Descent ofMan, ed. B. G. Campbell, pp. 58—86. Chicago: Aldine Press.
A biologist's world view. Science, 175:49—50.
With H. Levene and B. Spassky. Effects of selection and migrationof geotactic and phototactic behavior of Drosophila: III. Proc. R.
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1973
With J. R. Powell and H. Levene. Chromosomal polymorphisms in
Drosophila pseudoobscura used for diagnosis of geographic origin.
Evolution, 26:553-59.
With F. J. Ayala. Temporal frequency changes of enzyme andchromosomal polymorphisms in natural populations of Drosophila. Proc. Natl. Acad. Sci. USA, 70:680-83.
Nothing in biology makes sense except in the light of evolution.
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Is there gene exchange between Drosophila pseudoobscura and Drosophila persimilis in their natural habitats? Am. Nat., 107:312-14.
Active dispersal and passive transport in Drosophila. Evolution,
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Is genetic diversity compatible with human equality? Soc. Biol.,
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Ethics and values in biological and cultural evolution. Zygon,
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L'evoluzione e l'omonozione. Accad. Naz. dei Lincei, Atti delColloquio L'origine dell Uomo, 13—31.
1974
With J. N. Ahearn, H. L. Carson, and K. Y. Kaneshiro. Ethologicalisolation among three species of the planitibia subgroup of
Hawaiian Drosophila. Proc. Natl. Acad. Sci. USA, 71:901-3.

212

BIOGRAPHICAL MEMOIRSWith C. L. Judson and O. Pavlovsky. Behavior in different environments of populations of Drosophila pseudoobscura selected forphototaxis and geotaxis. Proc. Natl. Acad. Sci. USA, 71:197476.
Advancement and obsolescence in science. The Great Ideas of Today,
pp. 52—61. Chicago: Encyclopaedia Britannica.
Chance and creativity in evolution. In: Studies in the Philosophy ofBiology, ed. F. J. Ayala and Th. Dobzhansky, pp. 307-38.
London: Macmillan.
Genetic analysis of hybrid sterility within the species Drosophila
pseudoobscura. Hereditas, 77:81—88.
With F. J. Ayala. A new subspecies of Drosophila pseudoobscura. PanPac. Entomol., 50:211-19.
With J. R. Powell. Rates of dispersal of Drosophila pseudoobscura andits relatives. Proc. R. Soc. London, 187:281-98.
Studies in the Philosophy of Biology, ed. F. J. Ayala and Th. Dobzhansky. London: Macmillan.
1975
With W. W . Anderson, O. Pavlovsky, J. R. Powell, and 1). Yardley.
Genetics of natural populations. XLII. Three decades of genetic change in Drosophila pseudoobscura. Evolution, 29:24—36.
With J. R. Powell. Drosophila pseudoobscura and its American relatives Drosophila persimilis and Drosophila miranda. In: Handbook of
Genetics, ed. R. King, vol. 3, pp. 537—87. New York: Plenum
Press.
With J. R. Powell. The willistoni group of the sibling species ofDrosophila. In: Handbook of Genetics, ed. R. King, vol. 3, pp. 589—
622. New York: Plenum Press.
With R. Felix, J. Guzman, L. Levine, O. Olvera, J. R. Powell, M. E.
de la Rosa, and V. M. Salceda. Population genetics of Mexican
Drosophila. I. Chromosomal variation in natural populations ofDrosophila pseudoobscura from Central Mexico. J. Hered., 66:
203-6.
With O. Pavlovsky. Unstable intermediates between Orinocan andInterior semispecies of Drosophila paulistorum. Evolution, 29:
242-48.
Analysis of incipient reproductive isolation within a species ofDrosophila. Proc. Natl. Acad. Sci. USA, 72:3638-41.
T

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1976
The myths of genetic predestination and of tabula rasa. Perspect.
Biol. Med.,'19:156-70.
The genetic predestination and the tabula rasa myths. Columbia
Today (March):30-35.
Organismic and molecular aspects of species formation. In: Molecular Evolution, ed. F. f. Ayala, pp. 95—105. Sunderland, Mass.:
Sinauer Associates.
With J. R. Powell. How far do fruitflies fly? Am. Sci., 64:179-85.
With J. R. Powell, J. Hook, and H. Wistrand. Genetics of natural
populations. XLIII. Further studies on rates of dispersal of
Drosophila pseudoobscura and its relatives. Genetics, 82:493-506.
With O. Pavlovsky and J. R. Powell. Partially successful attempt toenhance reproductive isolation between semispecies of Drosophila paulistorum. Evolution, 30:201-12.
With R. C. Richmond. Genetic differentiation within the Andean
semispecies oi Drosophila paulistorum. Evolution, 30:746—56.
With H. Levene. Homeostatic drive counteracting selection for
positive and negative phototaxis and geotaxis in Drosophila
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1977
With F. J. Ayala, G. L. Stebbins, and J. W. Valentine. Evolution, xiv+ 572 pp. San Francisco: Freeman.
Determinismes genetiques mono- et polyfactoriels des comportements. In: Mecanismes Ethologiques de I'Evolution, ed. }. Medioni

and E. Boesiger, pp. 5—16. Paris: Masson.
Man in the universe. In: Man's Place in the Universe, pp. 79-92.
Tucson: University of Arizona.
With F. J. Ayala. Humankind—A product of evolutionary transcendence (Raymond Dart Lectures). Johannesburg: Witwatersrand University Press. 15 pp.
1980
The Roving Naturalist. Travel Letters of Theodosius Dobzhansky, ed.

Bentley Glass. 327 pp. Philadelphia: American PhilosophicalSociety.