Genetics and the Origin of Species

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Genetics and the Origin of Species by Dobzhansky, first edition.jpeg
Cover of the first (1937) edition
Author Theodosius Dobzhansky
Series Columbia University Biological Series (volume 11)
Subject Evolutionary biology
Published Columbia University Press
Pages 364
OCLC 766405
LC Class QH366 .D6

Genetics and the Origin of Species is a 1937 book by the Ukrainian-American evolutionary biologist Theodosius Dobzhansky. It is regarded as one of the most important works of the modern evolutionary synthesis. The book popularized the work of population genetics to other biologists, and influenced their appreciation for the genetic basis of evolution.1 In his book, Dobzhansky applied the theoretical work of Sewall Wright (1889-1988) to the study of natural populations, allowing him to address evolutionary problems in a novel way during his time. Dobzhansky implements theories of mutation, natural selection, and speciation throughout his book to explain habits of populations and the resulting effects on their genetic behavior.2 The book explains evolution in depth as a process over time that accounts for the diversity of all life on Earth. The study of evolution was present, but greatly neglected at the time. Dobzhansky illustrates that evolution regarding the origin and nature of species during this time in history was deemed mysterious, but had expanding potential for progress to be made in its field.3

Background

In Darwin's theory of natural selection, more organisms are produced than can survive. Some have variations that give them a competitive advantage, and they have the best chance of surviving and procreating. The main element lacking in the theory was any mechanism that would allow organisms to pass on these favorable variations. Lacking such a mechanism, the theory of evolution faced competition from theories such as neo-Lamarckism, in which the environment acted directly on organisms, changing their structures. Darwin did not know that the monk Gregor Mendel was already working on experiments that would explain inheritance in terms of units of heredity that we now call genes.4

When Mendelian genetics was rediscovered by several scientists, it initially increased the confusion. The Dutch botanist Hugo de Vries developed a theory called mutationism in which most variations were inconsequential and could not lead to species change. Instead, new species were formed by large mutations.4 At first, geneticists tended to support mutationism; but in the 1920s and 1930s a group of theoretical geneticists – particularly Ronald Fisher, J. B. S. Haldane and Sewall Wright – showed that Mendel's laws could explain continuous variation in biological characteristics; and that natural selection could act cumulatively, giving rise to large changes. Their work provided a theoretical framework for incorporating genetics into the theory of evolution.4

Many biologists fell into two camps: the geneticists, who mostly worked in the laboratory; and naturalists, who studied natural populations in the field and museums, and put much of their effort into taxonomy. Each contributed concepts that were essential to the understanding of evolution. Naturalists introduced the biological species concept, the definition of species as a community that is reproductively isolated and occupies a distinctive ecological niche.5:273 They also recognized that species are polytypic, having variations in time and space; and that behavior and change of function can give rise to evolutionary change.5:570

The two groups used such different methods and terminology that it was difficult for them to communicate. They were often battling over the same scarce academic resources, and each was often scornful of the other. As the paleontologist George Gaylord Simpson put it, paleontologists believed that "a geneticist was a person who shut himself in a room, pulled down the shades, watched small flies disporting themselves in milk bottles, and thought that he was studying nature." Meanwhile, naturalists were "like a man who undertakes to study the principles of the internal combustion engine by standing on a street corner and watching the motor cars whiz by."6

Publication

The book began as a series of lectures at Columbia University in October and November 1936. Dobzhansky decided to attend the summer 1936 meeting of the Genetics Society of America in Woods Hole, Massachusetts. When the geneticist Leslie Dunn learned of this, he invited Dobzhansky to give a series of lectures at Columbia. He sent the invitation in April, and within a month he had suggested that the lectures be a springboard for writing a general treatise on evolutionary genetics. Dobzhansky was enthusiastic, and in May he wrote back, proposing the title "Genetics and the Origin of Species". He envisioned two parts – "part I containing data on the sources of evolutionary change, and part II containing a discussion of their interactions leading to race- and species formation."7 After the lectures (for which he received $500), Dobzhansky returned to Pasadena, and in December Columbia University Press accepted his proposal for a book. The pace of writing was helped by a riding accident in February 1937 in which he crushed his knee, rendering him immobile; and by April he was able to send a manuscript to Dunn for his perusal.7

While reading the manuscript, Dunn persuaded the university to revive the Jesup lectures, a series that had involved some notable lecturers in the past. It was back-dated so that Dobzhansky's lectures became the first in the series. The Columbia University Biological Series was also revived, and when Genetics and the Origin of Species was published in October 1937 it became the 11th volume in that series.7

Three main editions were published in 1937, 1941 and 1951, each with significant changes. Dobzhansky considered Genetics of the Evolutionary Process (1970) a fourth edition, but one so much changed that it needed a new title.8:1669

Experiments

Through his work on Drosophila pseudoobscura, a species of fruitfly, Dobzhansky was able to identify that some populations of this species did not have identical sets of genes. Dobzhansky used experimental breeding in laboratories and gardens, and also surveys related to species in nature to help support the aspects of organic evolution. The data in his book shows the different genetic mutations and chromosomal changes that were observed. These experiments are vital to this book because they illustrate a transition from the laboratory to the greater field of genetics. Drosophila enabled researchers to gain a deeper understanding of how scientific knowledge about heredity has expanded and contributed to other areas of biology. By focusing on the opportunities and constraints of the research organism, persuasive accounts of the chromosomal genetics of Drosophila eventually evolved into the genetics of natural populations in the 1930s. All of the results from his experiments support the theory of modern evolutionary synthesis.10

Mutations

Through his experiments, Dobzhansky discovers that mutations of genes lead to evolution within a specific species. Adaptations play a large role in genetic drift, and it is known that genes and mutations influence this genetic drift in a particular environment. Mutations can result from external influences within the surrounding environment, especially if an organism inhabits an area with harsh living conditions. An organism can adapt to its environment in order to better suit its own needs. When an organism successfully adapts, it has higher survival and reproduction rate. Therefore, there is a higher chance its genes will be passed on to its offspring. Specific genes and alleles are then passed on to future generations to continue the trend of modern evolution that Dobzhansky presents in the book.11

Dobzhansky said natural mutation, aided by variation, can lead to change when acted upon by natural selection.12 Mutations were thought to be relatively rare and other variations were even considered to be harmful. Since an organism's overall genetic make-up was the result of natural selection, with damaging mutations weeded out, wild populations were assumed to have very little mutations. As a result, evolution was said to be a relatively slow process. One of Dobzhansky's major contributions in this book was to show that this view of slow-moving evolution was incorrect. While analyzing chromosome structure in wild populations of Drosophila pseudoobscura, Dobzhansky discovered a surprising amount of undiscovered variability. These variations could not be observed in the outward appearance of the individual organisms. Dobzhansky suggested that preservation of extensive variation would allow populations to evolve rapidly as environmental conditions change. This book was an novel landmark in the evolutionary synthesis, as it presented the union of Mendelian genetics and Darwinian theory.13

In Genetics and the Origin of Species, polyploidy is considered as a type of mutation. Polyploid cells have a chromosome number that is more than twice the haploid number. The effects of polyploidy between two different species causes hybridization and even greater evolution.3

Natural selection and speciation

Natural selection in an environment produces reproductive success, which benefits the species. Speciation is an process of evolution through which new biological species are formed. By studying the specifics of sexual, physiological, and behavioral isolating mechanisms in Drosophila pseudoobscura and Drosophila paulistrorum, Dobzhansky showed that varying degrees of reproductive isolation represented speciation in the process. Like many of his other studies, Dobzhansky's work on reproductive isolation was aimed at studying the process of evolution in action.13 Bringing samples from each population back into the laboratory, Dobzhansky showed that he could vary environmental conditions so as to produce the same changes in frequency of inversion patterns that were observed with changing seasons in the field. Dobzhansky concluded that such seasonal fluctuations were the result of natural selection at work, with temperature acting as the selecting agent. These masterful studies provided concrete support for the theory of natural selection, at the same time illustrating the fruitfulness of combining field and laboratory work in the study of evolution.13 Adaptive evolution occurs through the dominance and survival of competing genes within a species. This is caused by increasing the frequency of those alleles whose phenotypic effects selfishly promote their own reproduction. Reproductive isolation slows gene flow and reduces the process of evolution. He also believed new species could not arise from single mutations and must be isolated from others of its species by time, geography, habitat, or breeding season.12

Overall Genetics and the Origin of Species shows the importance how genes, mutations, and chromosomal changes influence evolution. The idea of isolation is also described in his work and how it is important for the establishment and maintenance of species and populations in nature.

Historical impact

Genetics and the Origin of Species provided the outline for a synthesis of genetics with evolution, and was enthusiastically received by both geneticists and naturalists. Dobzhansky laid out an advanced account of the evolutionary process in genetic terms, and he backed up his work with experimental evidence supporting the theoretical arguments. This led to the stimulation of the field of evolutionary genetics, and contributions to the theory soon began to follow. This had a powerful impact on naturalists and experimental biologists, who quickly embraced this new understanding of the evolutionary process as one of genetic change in populations.14 It was not long before the synthesis was broadened to include paleontology, systematics and botany in a series of notable books: Systematics and the Origin of Species (1942) by Ernst Mayr; Tempo and Mode in Evolution (1944) by George Gaylord Simpson; and Variation and Evolution in Plants (1950) by G. Ledyard Stebbins.15 The emerging synthesis was called the evolutionary synthesis by Julian Huxley in his book, Evolution: The Modern Synthesis.16:19 In 1947, a diverse collection of biologists met at a symposium in Princeton and declared their acceptance of this synthesis. However, it was not yet complete. Developmental biologists did not accept that the theory explained their observations, and it was not until the 1970s and 1980s that molecular biology bridged the gap. Also, for decades there was disagreement over whether the unit of selection was the gene or the individual as a whole.17

In 1974 all the living founders of the modern synthesis (with the exception of Simpson and Bernhard Rensch) met with historians of biology in a conference to evaluate their work. All acknowledged the Genetics and the Origin of Species was the direct instigator of all the work that followed.18 Ernst Mayr, in The Growth of Biological Thought, said that it was "clearly the most decisive event in the history of evolutionary biology since the publication of the Origin of Species in 1859. 5:569

Awards

Dobzhansky was plagued by a form of leukemia in his later years, but he remained vigorously active until the day before his death on December 18, 1975.13 During his lifetime he was the recipient of many honors and awards. For Genetics and the Origin of Species Dobzhansky was awarded the Daniel Giraud Elliot Medal from the National Academy of Sciences in 1941.19 Sixty years after its publication, the National Academy of Sciences commissioned a book entitled Genetics and the Origin of Species: From Darwin to Molecular Biology 60 Years After Dobzhansky.20

It was also included in the 1990 edition of Great Books of the Western World, placing it with Charles Darwin's two great works The Origin of Species and the Descent of Man. A third edition was published in 1951.

References

  1. ^ Futuyma, Douglas J. (2005). Evolution (3rd print. ed.). Sunderland, Mass.: Sinauer Associates. ISBN 978-0878931873. 
  2. ^ Ackert, Jr., Lloyd T. (2000). "Theodosius Grigor'evich Dobzhansky". In Schlager, Neil; Lauer, Josh. Science and Its Times : Understanding the Social Significance of Scientific Discovery. Volume 6: 1900–1949. Gale. pp. 160–161. ISBN 978-0787639327. 
  3. ^ a b Dobzhansky, Theodosius (1982). Genetics and the origin of species (Reprint. ed.). New York: Columbia University Press. p. 8. ISBN 978-0231054751. 
  4. ^ a b c Ayala, Francisco J.; Walter M. Fitch (22 July 1997). "Genetics and the origin of species: An introduction". Proceedings of the National Academy of Sciences of the United States of America 94 (15): 7691–7697. Retrieved 13 April 2014. 
  5. ^ a b c Mayr, Ernst (2000). The growth of biological thought : diversity, evolution, and inheritance (12. print. ed.). Cambridge: Harvard University Press. ISBN 9780674364462. 
  6. ^ Ceccarelli, Leah (2001). Shaping science with rhetoric : the cases of Dobzhansky, Schrödinger, and Wilson. Chicago, Illinois: University of Chicago Press. pp. 13–60. ISBN 9780226099071. 
  7. ^ a b c Cain, Joe (2002). "Co-opting colleagues: Appropriating Dobzhansky's 1936 lectures at Columbia". Journal of the History of Biology 35: 207–219. 
  8. ^ Ayala, Francisco J. (1985). "Theodosius Dobzhansky (1900–1975)". Biographical memoirs. National Academy of Sciences. Retrieved 14 April 2014. 
  9. ^ Dobzhansky, Theodosius (1970). Genetics of the evolutionary process (4th ed.). New York: Columbia university press. ISBN 978-0231083065. 
  10. ^ Kohler, Robert E. (1994). Lords of the fly : Drosophila genetics and the experimental life (Nachdr. ed.). Chicago: University of Chicago Press. pp. 250–254. ISBN 9780226450636. 
  11. ^ Futuyma, D. J. Evolutionary Biology. Sunderland, Mass: Sinauer Associates, Inc., 1986. p. 9.
  12. ^ a b Landauer, Lyndall B. (2000). "The Genetic Foundation of Natural Selection". In Schlager, Neil; Lauer, Josh. Science and Its Times : Understanding the Social Significance of Scientific Discovery. Volume 5: 1900–1949. Gale. pp. 102–104. ISBN 978-0787639327. 
  13. ^ a b c d "Theodosius Dobzhansky". Encyclopedia of World Biography 5. Gale. 1997. pp. 35–37. 
  14. ^ Jr., Lloyd T. Ackert. "Theodosius Grigor'evich Dobzhansky." In Science and Its Times, 160-61. Detroit: Gale, 2000, p. 160-161.
  15. ^ Powell, Jeffrey R. (November 1987). ""In the Air" - Theodosius Dobzhansky's Genetics and the Origin of Species". Genetics 117: 363–366. 
  16. ^ Smokovitis, Vassiliki Betty (1996). Unifying biology : the evolutionary synthesis and evolutionary biology. Princeton, NJ: Princeton Univ. Press. ISBN 9780691033433. 
  17. ^ Mayr, Ernst; Provine, William B., eds. (1998). The Evolutionary synthesis : perspectives on the unification of biology (New ed.). Cambridge, Mass.: Harvard University Press. pp. xii–xiii. ISBN 9780674272262. 
  18. ^ Dobzhansky, Theodosius (1982). "Introduction by Stephen Jay Gould". Genetics and the origin of species (Reprint ed.). New York: Columbia University Press. pp. xvii–xxxix. ISBN 978-0231054751. 
  19. ^ "Daniel Giraud Elliot Medal". National Academy of Sciences. Retrieved 16 February 2011. 
  20. ^ Ayala, Francisco J.; Fitch, Walter M., eds. (1997). Genetics and the origin of species : from Darwin to molecular biology, 60 years after Dobzhansky. Washington, D.C.: National Academy of Sciences. ISBN 978-0309058773. 

Further reading

  • Carson, Hampton L. (1998). "Cytogenetics and the Neo-Darwinian synthesis". In Mayr, Ernst; Provine, William B. The Evolutionary synthesis : perspectives on the unification of biology ([New ed]. ed.). Cambridge, Mass.: Harvard University Press. pp. 86–95. ISBN 9780674272262. 
  • Ceccarelli, Leah (2001). Shaping science with rhetoric : the cases of Dobzhansky, Schrödinger, and Wilson. Chicago, Illinois: University of Chicago Press. pp. 13–60. ISBN 9780226099071. 
  • Coyne, Jerry A. (18 August 1995). "Dobzhansky Revisited". Science 269 (5226): 991–992. doi:10.1126/science.269.5226.991. 
  • Lewontin, Richard C. (October 1997). "Dobzhansky's Genetics and the Origin of Species: Is it still relevant?". Genetics 147: 351–355. 
  • Mayr, Ernst (1999). Systematics and the origin of species, from the viewpoint of a zoologist (1. Harvard Univ. Press pbk. ed.). Cambridge, Mass: Harvard Univ. Press. pp. xv–xvii. ISBN 9780674862500. 
  • Orr, H. Allen (December 1996). "Dobzhansky, Bateson and the genetics of speciation". Genetics 144: 1331–1335. 
  • Provine, William B. (1994). "The Origin of Dobzhansky's Genetics and the Origin of Species". In Adams, Mark B. The evolution of Theodosius Dobzhansky : essays on his life and thought in Russia and America ; [selected papers from the International Symposium on Theodosius Dobzhansky, held in Leningrad 17-19 September 1990]. Princeton, NJ: Princeton University Press. pp. 99–114. ISBN 978-0691034799. 
  • Smokovitis, Vassiliki Betty (1996). Unifying biology : the evolutionary synthesis and evolutionary biology. Princeton, NJ: Princeton Univ. Press. ISBN 9780691033433. 

External links