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Thomas Hunt Morgan (September 25, 1866 – December 4, 1945) was an American
evolutionary biologist Evolutionary biology is the subfield of biology that studies the evolutionary processes such as natural selection, common descent, and speciation that produced the diversity of life on Earth. In the 1930s, the discipline of evolutionary biol ...
,
geneticist A geneticist is a biologist or physician who studies genetics, the science of genes, heredity, and variation of organisms. A geneticist can be employed as a scientist or a lecturer. Geneticists may perform general research on genetic process ...
,
embryologist Embryology (from Greek ἔμβρυον, ''embryon'', "the unborn, embryo"; and -λογία, ''-logia'') is the branch of animal biology that studies the prenatal development of gametes (sex cells), fertilization, and development of embryos and ...
, and science author who won the
Nobel Prize in Physiology or Medicine The Nobel Prize in Physiology or Medicine () is awarded yearly by the Nobel Assembly at the Karolinska Institute for outstanding discoveries in physiology or medicine. The Nobel Prize is not a single prize, but five separate prizes that, acco ...
in 1933 for discoveries elucidating the role that the
chromosome A chromosome is a package of DNA containing part or all of the genetic material of an organism. In most chromosomes, the very long thin DNA fibers are coated with nucleosome-forming packaging proteins; in eukaryotic cells, the most import ...
plays in
heredity Heredity, also called inheritance or biological inheritance, is the passing on of traits from parents to their offspring; either through asexual reproduction or sexual reproduction, the offspring cells or organisms acquire the genetic infor ...
. Morgan received his Ph.D. from
Johns Hopkins University The Johns Hopkins University (often abbreviated as Johns Hopkins, Hopkins, or JHU) is a private university, private research university in Baltimore, Maryland, United States. Founded in 1876 based on the European research institution model, J ...
in
zoology Zoology ( , ) is the scientific study of animals. Its studies include the anatomy, structure, embryology, Biological classification, classification, Ethology, habits, and distribution of all animals, both living and extinction, extinct, and ...
in 1890 and researched embryology during his tenure at Bryn Mawr. Following the rediscovery of
Mendelian inheritance Mendelian inheritance (also known as Mendelism) is a type of biological inheritance following the principles originally proposed by Gregor Mendel in 1865 and 1866, re-discovered in 1900 by Hugo de Vries and Carl Correns, and later popularize ...
in 1900, Morgan began to study the genetic characteristics of the fruit fly ''
Drosophila melanogaster ''Drosophila melanogaster'' is a species of fly (an insect of the Order (biology), order Diptera) in the family Drosophilidae. The species is often referred to as the fruit fly or lesser fruit fly, or less commonly the "vinegar fly", "pomace fly" ...
''. In his famous Fly Room at
Columbia University Columbia University in the City of New York, commonly referred to as Columbia University, is a Private university, private Ivy League research university in New York City. Established in 1754 as King's College on the grounds of Trinity Churc ...
's Schermerhorn Hall, Morgan demonstrated that
gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...
s are carried on
chromosome A chromosome is a package of DNA containing part or all of the genetic material of an organism. In most chromosomes, the very long thin DNA fibers are coated with nucleosome-forming packaging proteins; in eukaryotic cells, the most import ...
s and are the mechanical basis of heredity. These discoveries formed the basis of the modern science of
genetics Genetics is the study of genes, genetic variation, and heredity in organisms.Hartl D, Jones E (2005) It is an important branch in biology because heredity is vital to organisms' evolution. Gregor Mendel, a Moravian Augustinians, Augustinian ...
. During his distinguished career, Morgan wrote 22 books and 370 scientific papers. As a result of his work, ''Drosophila'' became a major
model organism A model organism is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the model organism will provide insight into the workings of other organisms. Mo ...
in contemporary genetics. The Division of Biology which he established at the
California Institute of Technology The California Institute of Technology (branded as Caltech) is a private research university in Pasadena, California, United States. The university is responsible for many modern scientific advancements and is among a small group of institutes ...
has produced seven Nobel Prize winners.


Early life and education

Morgan was born in Lexington,
Kentucky Kentucky (, ), officially the Commonwealth of Kentucky, is a landlocked U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders Illinois, Indiana, and Ohio to the north, West Virginia to the ...
, to Charlton Hunt Morgan and Ellen Key Howard Morgan.Sturtevant (1959), p. 283. Part of a line of Southern plantation and slave owners on his father's side, Morgan was a nephew of
Confederate A confederation (also known as a confederacy or league) is a political union of sovereign states united for purposes of common action. Usually created by a treaty, confederations of states tend to be established for dealing with critical issu ...
General John Hunt Morgan; his great-grandfather John Wesley Hunt had been one of the first millionaires west of the
Allegheny Mountains The Allegheny Mountain Range ( ) — also spelled Alleghany or Allegany, less formally the Alleghenies — is part of the vast Appalachian Mountain Range of the Eastern United States and Canada. Historically it represented a significant barr ...
. Through his mother, he was the great-grandson of
Francis Scott Key Francis Scott Key (August 1, 1779January 11, 1843) was an American lawyer, author, and poet from Frederick, Maryland, best known as the author of the poem "Defence of Fort M'Henry" which was set to a popular British tune and eventually became t ...
, the author of the " Star Spangled Banner", and
John Eager Howard John Eager Howard (June 4, 1752October 12, 1827) was an American soldier and politician from Maryland. He was elected as governor of the state in 1788, and served three one-year terms. He also was elected to the Continental Congress, the Congre ...
, governor and senator from
Maryland Maryland ( ) is a U.S. state, state in the Mid-Atlantic (United States), Mid-Atlantic region of the United States. It borders the states of Virginia to its south, West Virginia to its west, Pennsylvania to its north, and Delaware to its east ...
. Following the Civil War, the family fell on hard times with the temporary loss of civil and some property rights for those who aided the Confederacy. His father had difficulty finding work in politics and spent much of his time coordinating veterans' reunions. Beginning at age 16 in the Preparatory Department, Morgan attended the State College of Kentucky (now the
University of Kentucky The University of Kentucky (UK, UKY, or U of K) is a Public University, public Land-grant University, land-grant research university in Lexington, Kentucky, United States. Founded in 1865 by John Bryan Bowman as the Agricultural and Mechanical ...
). He focused on science; he particularly enjoyed natural history, and worked with the
U.S. Geological Survey The United States Geological Survey (USGS), founded as the Geological Survey, is an agency of the U.S. Department of the Interior whose work spans the disciplines of biology, geography, geology, and hydrology. The agency was founded on March ...
in his summers. He graduated as
valedictorian Valedictorian is an academic title for the class rank, highest-performing student of a graduation, graduating class of an academic institution in the United States. The valedictorian is generally determined by an academic institution's grade poin ...
in 1886 with a Bachelor of Science degree. Following a summer at the Marine Biology School in Annisquam, Massachusetts, Morgan began graduate studies in
zoology Zoology ( , ) is the scientific study of animals. Its studies include the anatomy, structure, embryology, Biological classification, classification, Ethology, habits, and distribution of all animals, both living and extinction, extinct, and ...
at the recently founded
Johns Hopkins University The Johns Hopkins University (often abbreviated as Johns Hopkins, Hopkins, or JHU) is a private university, private research university in Baltimore, Maryland, United States. Founded in 1876 based on the European research institution model, J ...
. After two years of experimental work with morphologist
William Keith Brooks William Keith Brooks (March 25, 1848 – November 12, 1908) was an American zoologist, born in Cleveland, Ohio, March 25, 1848. Brooks studied embryological development in invertebrates and founded a marine biological laboratory where he and othe ...
and writing several publications, Morgan was eligible to receive a Master of Science from the State College of Kentucky in 1888. The college required two years of study at another institution and an examination by the college faculty. The college offered Morgan a full professorship; however, he chose to stay at Johns Hopkins and was awarded a relatively large fellowship to help him fund his studies. Under Brooks, Morgan completed his thesis work on the embryology of
sea spider Sea spiders are marine arthropods of the class (biology), class Pycnogonida, hence they are also called pycnogonids (; named after ''Pycnogonum'', the type genus; with the suffix '). The class includes the only now-living order (biology), order P ...
s—collected during the summers of 1889 and 1890 at the
Marine Biological Laboratory The Marine Biological Laboratory (MBL) is an international center for research and education in biological and environmental science. Founded in Woods Hole, Massachusetts, in 1888, the MBL is a private, nonprofit institution that was independent ...
in
Woods Hole, Massachusetts Woods Hole is a census-designated place in the town of Falmouth in Barnstable County, Massachusetts, United States. It lies at the extreme southwestern corner of Cape Cod, near Martha's Vineyard and the Elizabeth Islands. The population was 78 ...
—to determine their
phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...
relationship with other
arthropod Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metam ...
s. He concluded that concerning embryology, they were more closely related to
spiders Spiders (order Araneae) are air-breathing arthropods that have eight limbs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude silk. They are the largest order of arachnids and rank seventh in total species di ...
than crustaceans. Based on the publication of this work, Morgan was awarded his Ph.D. from Johns Hopkins in 1890 and was also awarded the Bruce Fellowship in Research. He used the fellowship to travel to
Jamaica Jamaica is an island country in the Caribbean Sea and the West Indies. At , it is the third-largest island—after Cuba and Hispaniola—of the Greater Antilles and the Caribbean. Jamaica lies about south of Cuba, west of Hispaniola (the is ...
, the Bahamas and
Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...
to conduct further research. Every summer from 1910 to 1925, Morgan and his colleagues at the famous Fly Room at Columbia University moved their research program to the
Marine Biological Laboratory The Marine Biological Laboratory (MBL) is an international center for research and education in biological and environmental science. Founded in Woods Hole, Massachusetts, in 1888, the MBL is a private, nonprofit institution that was independent ...
. Aside from being an independent investigator at the MBL from 1890 to 1942, he became very involved in the governance of the institution, including serving as an MBL trustee from 1897 to 1945.


Career and research


Bryn Mawr

In 1890, Morgan was appointed associate professor (and head of the biology department) at Johns Hopkins' sister school
Bryn Mawr College Bryn Mawr College ( ; Welsh language, Welsh: ) is a Private college, private Women's colleges in the United States, women's Liberal arts colleges in the United States, liberal arts college in Bryn Mawr, Pennsylvania, United States. Founded as a ...
, replacing his colleague
Edmund Beecher Wilson Edmund Beecher Wilson (October 19, 1856 – March 3, 1939) was a pioneering American zoologist and geneticist. He wrote one of the most influential textbooks in modern biology, ''The Cell''. He discovered the chromosomal XY sex-determination s ...
. Morgan taught all morphology-related courses, while the other member of the department, Jacques Loeb, taught the physiological courses. Although Loeb stayed for only one year, it was the beginning of their lifelong friendship. Morgan lectured in biology five days a week, giving two lectures a day. He frequently included his recent research in his lectures. Although an enthusiastic teacher, he was most interested in research in the laboratory. During the first few years at Bryn Mawr, he produced descriptive studies of
sea acorn ''Balanus'' is a genus of barnacles in the family (biology), family Balanidae of the subphylum Crustacea. This genus is known in the fossil record from the Jurassic to the Quaternary periods (age range: from 189.6 to 0.0 million years ago.). F ...
s, ascidian worms, and frogs. In 1894 Morgan was granted a year's absence to conduct research in the laboratories of ''
Stazione Zoologica The Stazione Zoologica Anton Dohrn is a research institute in Naples, Italy, devoted to basic research in biology. Research is largely interdisciplinary involving the fields of evolution, biochemistry, molecular biology, neurobiology, cell biol ...
'' in
Naples Naples ( ; ; ) is the Regions of Italy, regional capital of Campania and the third-largest city of Italy, after Rome and Milan, with a population of 908,082 within the city's administrative limits as of 2025, while its Metropolitan City of N ...
, where Wilson had worked two years earlier. There he worked with German biologist
Hans Driesch Hans Adolf Eduard Driesch (28 October 1867 – 17 April 1941) was a German biologist and philosopher from Bad Kreuznach. He is most noted for his early experimental work in embryology and for his neo-vitalist philosophy of entelechy. He has also ...
, whose research in the experimental study of development piqued Morgan's interest. Among other projects that year, Morgan completed an experimental study of
ctenophore Ctenophora (; : ctenophore ) is a phylum of marine invertebrates, commonly known as comb jellies, that inhabit sea waters worldwide. They are notable for the groups of cilia they use for swimming (commonly referred to as "combs"), and they ar ...
embryology. In Naples and through Loeb, he became familiar with the ''Entwicklungsmechanik'' (roughly, "developmental mechanics") school of experimental biology. It was a reaction to the vitalistic ''
Naturphilosophie "''Naturphilosophie''" (German for "nature-philosophy") is a term used in English-language philosophy to identify a current in the philosophical tradition of German idealism, as applied to the study of nature in the earlier 19th century. German ...
'', which was extremely influential in 19th-century morphology. Morgan changed his work from traditional, largely descriptive morphology to experimental embryology that sought physical and chemical explanations for organismal development. At the time, there was considerable scientific debate over the question of how an embryo developed. Following Wilhelm Roux's mosaic theory of development, some believed that hereditary material was divided among embryonic cells, which were predestined to form particular parts of a mature organism. Driesch and others thought that development was due to epigenetic factors, where interactions between the protoplasm and the nucleus of the egg and the environment could affect development. Morgan was in the latter camp; his work with Driesch demonstrated that
blastomeres In biology, a blastomere is a type of cell produced by cell division (cleavage) of the zygote after fertilization; blastomeres are an essential part of blastula formation, and blastocyst formation in mammals. Human blastomere characteristics In ...
isolated from
sea urchin Sea urchins or urchins () are echinoderms in the class (biology), class Echinoidea. About 950 species live on the seabed, inhabiting all oceans and depth zones from the intertidal zone to deep seas of . They typically have a globular body cove ...
and ctenophore eggs could develop into complete larvae, contrary to the predictions (and experimental evidence) of Roux's supporters. A related debate involved the role of
epigenetic In biology, epigenetics is the study of changes in gene expression that happen without changes to the DNA sequence. The Greek prefix ''epi-'' (ἐπι- "over, outside of, around") in ''epigenetics'' implies features that are "on top of" or "in ...
and environmental factors in development; on this front Morgan showed that
sea urchin Sea urchins or urchins () are echinoderms in the class (biology), class Echinoidea. About 950 species live on the seabed, inhabiting all oceans and depth zones from the intertidal zone to deep seas of . They typically have a globular body cove ...
eggs could be induced to divide without fertilization by adding
magnesium chloride Magnesium chloride is an inorganic compound with the formula . It forms hydrates , where ''n'' can range from 1 to 12. These salts are colorless or white solids that are highly soluble in water. These compounds and their solutions, both of which ...
. Loeb continued this work and became well known for creating fatherless frogs using the method. When Morgan returned to Bryn Mawr in 1895, he was promoted to full professor. Morgan's main lines of experimental work involved regeneration and larval development; in each case, his goal was to distinguish internal and external causes to shed light on the Roux-Driesch debate. He wrote his first book, ''The Development of the Frog's Egg'' (1897). He began a series of studies on different organisms' ability to regenerate. He looked at grafting and regeneration in tadpoles, fish, and earthworms; in 1901 he published his research as ''Regeneration''. Beginning in 1900, Morgan started working on the problem of sex determination, which he had previously dismissed when Nettie Stevens discovered the impact of the Y chromosome on sex. He also continued to study the evolutionary problems that had been the focus of his earliest work.


Columbia University

Morgan worked at Columbia University for 24 years, from 1904 until 1928 when he left for a position at the California Institute of Technology. In 1904, his friend, Jofi Joseph died of tuberculosis, and he felt he ought to mourn her, though E. B. Wilson—still blazing the path for his younger friend—invited Morgan to join him at
Columbia University Columbia University in the City of New York, commonly referred to as Columbia University, is a Private university, private Ivy League research university in New York City. Established in 1754 as King's College on the grounds of Trinity Churc ...
. This move freed him to focus fully on experimental work. When Morgan took the professorship in experimental zoology, he became increasingly focused on the mechanisms of heredity and evolution. He published ''Evolution and Adaptation'' (1903); like many biologists at the time, he saw evidence for biological evolution (as in the
common descent Common descent is a concept in evolutionary biology applicable when one species is the ancestor of two or more species later in time. According to modern evolutionary biology, all living beings could be descendants of a unique ancestor commonl ...
of similar species) but rejected Darwin's proposed mechanism of
natural selection Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the Heredity, heritable traits characteristic of a population over generation ...
acting on small, constantly produced variations. Extensive work in
biometry Biostatistics (also known as biometry) is a branch of statistics that applies statistical methods to a wide range of topics in biology. It encompasses the design of biological experiments, the collection and analysis of data from those experime ...
seemed to indicate that continuous natural variation had distinct limits and did not represent heritable changes. Embryological development posed an additional problem in Morgan's view, as selection could not act on the early, incomplete stages of highly complex organs such as the eye. The common solution of the Lamarckian mechanism of inheritance of acquired characters, which featured prominently in Darwin's theory, was increasingly rejected by biologists. According to Morgan's biographer Garland Allen, he was also hindered by his views on taxonomy: he thought that species were entirely artificial creations that distorted the continuously variable range of real forms, while he held a "typological" view of larger taxa and could see no way that one such group could transform into another. But while Morgan was skeptical of natural selection for many years, his theories of heredity and variation were radically transformed through his conversion to Mendelism. In 1900 three scientists,
Carl Correns Carl Erich Correns (19 September 1864 – 14 February 1933) was a German botanist and geneticist notable primarily for his independent discovery of the principles of heredity, which he achieved simultaneously but independently of the botanist ...
,
Erich von Tschermak Erich Tschermak, Edler von Seysenegg (15 November 1871 – 11 October 1962) was an Austrian agronomist who developed several new disease-resistant crops, including wheat-rye and oat hybrids. He was a son of the Moravia-born mineralogist Gusta ...
and
Hugo De Vries Hugo Marie de Vries (; 16 February 1848 – 21 May 1935) was a Dutch botanist and one of the first geneticists. He is known chiefly for suggesting the concept of genes, rediscovering the laws of heredity in the 1890s while apparently unaware of ...
, had rediscovered the work of
Gregor Mendel Gregor Johann Mendel Order of Saint Augustine, OSA (; ; ; 20 July 1822 – 6 January 1884) was an Austrian Empire, Austrian biologist, meteorologist, mathematician, Augustinians, Augustinian friar and abbot of St Thomas's Abbey, Brno, St. Thom ...
, and with it the foundation of
genetics Genetics is the study of genes, genetic variation, and heredity in organisms.Hartl D, Jones E (2005) It is an important branch in biology because heredity is vital to organisms' evolution. Gregor Mendel, a Moravian Augustinians, Augustinian ...
. De Vries proposed that new species were created by mutation, bypassing the need for either Lamarckism or Darwinism. As Morgan had dismissed both evolutionary theories, he was seeking to prove De Vries' mutation theory with his experimental heredity work. He was initially skeptical of Mendel's laws of heredity (as well as the related chromosomal theory of sex determination), which were being considered as a possible basis for natural selection. Following C. W. Woodworth and William E. Castle, around 1908 Morgan started working on the fruit fly ''
Drosophila melanogaster ''Drosophila melanogaster'' is a species of fly (an insect of the Order (biology), order Diptera) in the family Drosophilidae. The species is often referred to as the fruit fly or lesser fruit fly, or less commonly the "vinegar fly", "pomace fly" ...
'', and encouraging students to do so as well. With Fernandus Payne, he mutated ''Drosophila'' through physical, chemical, and radiational means. He began cross-breeding experiments to find heritable mutations, but they had no significant success for two years.Kohler, ''Lords of the Fly'', pp. 37–43 Castle had also had difficulty identifying mutations in ''Drosophila'', which were tiny. Finally, in 1909, a series of heritable mutants appeared, some of which displayed Mendelian inheritance patterns; in 1910 Morgan noticed a white-eyed
mutant In biology, and especially in genetics, a mutant is an organism or a new genetic character arising or resulting from an instance of mutation, which is generally an alteration of the DNA sequence of the genome or chromosome of an organism. It i ...
male among the red-eyed
wild type The wild type (WT) is the phenotype of the typical form of a species as it occurs in nature. Originally, the wild type was conceptualized as a product of the standard "normal" allele at a locus, in contrast to that produced by a non-standard, " ...
s. When white-eyed flies were bred with a red-eyed female, their progeny were all red-eyed. A second-generation cross produced white-eyed males—a sex-linked recessive trait, the gene for which Morgan named ''
white White is the lightest color and is achromatic (having no chroma). It is the color of objects such as snow, chalk, and milk, and is the opposite of black. White objects fully (or almost fully) reflect and scatter all the visible wa ...
''. Morgan also discovered a pink-eyed mutant that showed a different pattern of inheritance. In a paper published in ''
Science Science is a systematic discipline that builds and organises knowledge in the form of testable hypotheses and predictions about the universe. Modern science is typically divided into twoor threemajor branches: the natural sciences, which stu ...
'' in 1911, he concluded that (1) some traits were
sex-linked Sex linkage describes the sex-specific patterns of inheritance and expression when a gene is present on a sex chromosome (allosome) rather than a non-sex chromosome (autosome). Genes situated on the X-chromosome are thus termed X-linked, and a ...
, (2) the trait was probably carried on one of the
sex chromosome Sex chromosomes (also referred to as allosomes, heterotypical chromosome, gonosomes, heterochromosomes, or idiochromosomes) are chromosomes that carry the genes that determine the sex of an individual. The human sex chromosomes are a typical pair ...
s, and (3) other genes were probably carried on specific chromosomes as well. Morgan and his students became more successful at finding mutant flies; they counted the mutant characteristics of thousands of fruit flies and studied their inheritance. As they accumulated multiple mutants, they combined them to study more complex inheritance patterns. The observation of a miniature-wing mutant, which was also on the sex chromosome but sometimes sorted independently to the white-eye mutation, led Morgan to the idea of
genetic linkage Genetic linkage is the tendency of Nucleic acid sequence, DNA sequences that are close together on a chromosome to be inherited together during the meiosis phase of sexual reproduction. Two Genetic marker, genetic markers that are physically near ...
and to hypothesize the phenomenon of crossing over. He relied on the discovery of
Frans Alfons Janssens Frans Alfons Ignace Maria Janssens (23 July 1863 – 8 October 1924) was Catholic priest and the discoverer of crossing-over of genes during meiosis, which he called "chiasmatypie". His work was continued by the Nobel Prize winner Thomas Hunt Morg ...
, a Belgian professor at the University of Leuven, who described the phenomenon in 1909 and had called it ''chiasmatypy''. Morgan proposed that the amount of crossing over between linked genes differs and that crossover frequency might indicate the distance separating genes on the chromosome. The later English geneticist J. B. S. Haldane suggested that the unit of measurement for linkage be called the morgan. Morgan's student
Alfred Sturtevant Alfred Henry Sturtevant (November 21, 1891 – April 5, 1970) was an American geneticist. Sturtevant constructed the first genetic map of a chromosome in 1911. Throughout his career he worked on the organism ''Drosophila melanogaster'' with ...
developed the first
genetic map Genetic linkage is the tendency of DNA sequences that are close together on a chromosome to be inherited together during the meiosis phase of sexual reproduction. Two genetic markers that are physically near to each other are unlikely to be separ ...
in 1913. In 1915 Morgan, Sturtevant,
Calvin Bridges Calvin Blackman Bridges (January 11, 1889 – December 27, 1938) was an American scientist known for his contributions to the field of genetics. Along with Alfred Sturtevant and H.J. Muller, Bridges was part of Thomas Hunt Morgan's famous "Fly R ...
and H. J. Muller wrote the seminal book ''The Mechanism of Mendelian Heredity''. Geneticist Curt Stern called the book "the fundamental textbook of the new genetics". In the following years, most biologists came to accept the Mendelian-chromosome theory, which was independently proposed by Walter Sutton and
Theodor Boveri Theodor Heinrich Boveri (12 October 1862 – 15 October 1915) was a German zoologist, comparative anatomist and co-founder of modern cytology. He was notable for the first hypothesis regarding cellular processes that cause cancer, and for descr ...
in 1902/1903, and elaborated and expanded by Morgan and his students. Garland Allen characterized the post-1915 period as one of
normal science Normal science, identified and elaborated on by Thomas Samuel Kuhn in ''The Structure of Scientific Revolutions'', is the regular work of scientists theorizing, observing, and experimenting within a settled paradigm or explanatory framework. Re ...
, in which "The activities of 'geneticists' were aimed at further elucidation of the details and implications of the Mendelian-chromosome theory developed between 1910 and 1915." But, the details of the increasingly complex theory, as well as the concept of the
gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...
and its physical nature, were still controversial. Critics such as W. E. Castle pointed to contrary results in other organisms, suggesting that genes interact with each other, while Richard Goldschmidt and others thought there was no compelling reason to view genes as discrete units residing on chromosomes. Because of Morgan's dramatic success with ''Drosophila'', many other labs throughout the world took up fruit fly genetics. Columbia became the center of an informal exchange network, through which promising mutant ''Drosophila'' strains were transferred from lab to lab; ''Drosophila'' became one of the first and for some time the most widely used,
model organism A model organism is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the model organism will provide insight into the workings of other organisms. Mo ...
s. Morgan's group remained highly productive, but Morgan largely withdrew from doing fly work and gave his lab members considerable freedom in designing and carrying out their own experiments. He returned to embryology and worked to encourage the spread of genetics research to other organisms and the spread of mechanistic experimental approach (''Enwicklungsmechanik'') to all biological fields. After 1915, he also became a strong critic of the growing
eugenics Eugenics is a set of largely discredited beliefs and practices that aim to improve the genetic quality of a human population. Historically, eugenicists have attempted to alter the frequency of various human phenotypes by inhibiting the fer ...
movement, which adopted genetic approaches in support of
racist Racism is the belief that groups of humans possess different behavioral traits corresponding to inherited attributes and can be divided based on the superiority of one Race (human categorization), race or ethnicity over another. It may also me ...
views of "improving" humanity. Morgan's fly-room at Columbia became world-famous, and he found it easy to attract funding and visiting academics. In 1927 after 25 years at Columbia, and nearing the age of retirement, he received an offer from
George Ellery Hale George Ellery Hale (June 29, 1868 – February 21, 1938) was an American astrophysicist, best known for his discovery of magnetic fields in sunspots, and as the leader or key figure in the planning or construction of several world-leading ...
to establish a school of biology in California.


Caltech

In 1928 Morgan joined the faculty of the
California Institute of Technology The California Institute of Technology (branded as Caltech) is a private research university in Pasadena, California, United States. The university is responsible for many modern scientific advancements and is among a small group of institutes ...
where he remained until his retirement 14 years later in 1942. Morgan moved to California to head the Division of Biology at the
California Institute of Technology The California Institute of Technology (branded as Caltech) is a private research university in Pasadena, California, United States. The university is responsible for many modern scientific advancements and is among a small group of institutes ...
in 1928. In establishing the biology division, Morgan wanted to distinguish his program from those offered by Johns Hopkins and Columbia, with research focused on genetics and evolution; experimental embryology; physiology; biophysics, and biochemistry. He was also instrumental in the establishment of the
Marine Laboratory Oceanography (), also known as oceanology, sea science, ocean science, and marine science, is the scientific study of the ocean, including its Physical oceanography, physics, Chemical oceanography, chemistry, Biological oceanography, biology, a ...
at Corona del Mar. He wanted to attract the best people to the Division at Caltech, so he took Bridges, Sturtevant, Jack Shultz and Albert Tyler from Columbia and took on
Theodosius Dobzhansky Theodosius Grigorievich Dobzhansky (; ; January 25, 1900 – December 18, 1975) was a Russian-born American geneticist and evolutionary biologist. He was a central figure in the field of evolutionary biology for his work in shaping the modern ...
as an international research fellow. More scientists came to work in the Division including George Beadle, Boris Ephrussi, Edward L. Tatum,
Linus Pauling Linus Carl Pauling ( ; February 28, 1901August 19, 1994) was an American chemist and peace activist. He published more than 1,200 papers and books, of which about 850 dealt with scientific topics. ''New Scientist'' called him one of the 20 gre ...
,
Frits Went Friedrich August Ferdinand Christian Went (June 18, 1863 – July 24, 1935) was a Dutch botanist. Went was born in Amsterdam. He was professor of botany and director of the Botanical Garden at the University of Utrecht. His eldest son was ...
, Edward B. Lewis, and Sidney W. Byance with his reputation, Morgan held numerous prestigious positions in American science organizations. From 1927 to 1931 Morgan served as the President of the National Academy of Sciences; in 1930 he was the President of the
American Association for the Advancement of Science The American Association for the Advancement of Science (AAAS) is a United States–based international nonprofit with the stated mission of promoting cooperation among scientists, defending scientific freedom, encouraging scientific responsib ...
; and in 1932 he chaired the Sixth International Congress of Genetics in
Ithaca, New York Ithaca () is a city in and the county seat of Tompkins County, New York, United States. Situated on the southern shore of Cayuga Lake in the Finger Lakes region of New York (state), New York, Ithaca is the largest community in the Ithaca metrop ...
. In 1933 Morgan was awarded the
Nobel Prize in Physiology or Medicine The Nobel Prize in Physiology or Medicine () is awarded yearly by the Nobel Assembly at the Karolinska Institute for outstanding discoveries in physiology or medicine. The Nobel Prize is not a single prize, but five separate prizes that, acco ...
; he had been nominated in 1919 and 1930 for the same work. As an acknowledgment of the group nature of his discovery, he gave his prize money to Bridges, Sturtevant, and his own children. Morgan declined to attend the awards ceremony in 1933, instead attending in 1934. The 1933 rediscovery of the giant polytene chromosomes in the salivary gland of ''Drosophila'' may have influenced his choice. Until that point, the lab's results had been inferred from phenotypic results, the visible polytene chromosome enabled them to confirm their results on a physical basis. Morgan's Nobel acceptance speech entitled "The Contribution of Genetics to Physiology and Medicine" downplayed the contribution genetics could make to medicine beyond
genetic counseling Genetic counseling is the process of investigating individuals and families affected by or at risk of genetic disorders to help them understand and adapt to the medical, psychological and familial implications of genetic contributions to disease. ...
. In 1939 he was awarded the
Copley Medal The Copley Medal is the most prestigious award of the Royal Society of the United Kingdom, conferred "for sustained, outstanding achievements in any field of science". The award alternates between the physical sciences or mathematics and the bio ...
by the Royal Society. He received two extensions of his contract at Caltech, but eventually retired in 1942, becoming a professor and chairman emeritus. George Beadle returned to Caltech to replace Morgan as chairman of the department in 1946. Although he had retired, Morgan kept offices across the road from the Division and continued laboratory work. In his retirement, he returned to the questions of sexual differentiation, regeneration, and embryology.


Death

Morgan had throughout his life suffered from a chronic
duodenal ulcer Peptic ulcer disease is when the inner part of the stomach's gastric mucosa (lining of the stomach), the first part of the small intestine, or sometimes the lower esophagus, gets damaged. An ulcer in the stomach is called a gastric ulcer, while ...
. In 1945, at age 79, he experienced a severe heart attack and died from a ruptured artery.


Morgan and evolution

Morgan was interested in evolution throughout his life. He wrote his thesis on the phylogeny of sea spiders (
pycnogonids Sea spiders are marine arthropods of the class (biology), class Pycnogonida, hence they are also called pycnogonids (; named after ''Pycnogonum'', the type genus; with the suffix '). The class includes the only now-living order (biology), order P ...
) and wrote four books about evolution. In ''Evolution and Adaptation'' (1903), he argued the anti-Darwinist position that selection could never produce wholly new species by acting on slight individual differences. He rejected Darwin's theory of sexual selection and the Neo-Lamarckian theory of the inheritance of acquired characters. Morgan was not the only scientist attacking natural selection. The period 1875–1925 has been called '
The eclipse of Darwinism Julian Huxley used the phrase "the eclipse of Darwinism" to describe the state of affairs prior to what he called the "modern synthesis". During the "eclipse", evolution was widely accepted in scientific circles but relatively few biologists be ...
'. After discovering many small stable heritable mutations in ''Drosophila'', Morgan gradually changed his mind. The relevance of mutations for evolution is that only characters that are inherited can have an effect on evolution. Since Morgan solved the problem of heredity (1915), he was in a unique position to examine critically Darwin's theory of natural selection. In '' A Critique of the Theory of Evolution'' (1916), Morgan discussed questions such as: "Does selection play any role in evolution? How can selection produce anything new? Is selection no more than the elimination of the unfit? Is selection a creative force?" After eliminating some misunderstandings and explaining in detail the new science of Mendelian heredity and its chromosomal basis, Morgan concludes, "the evidence shows clearly that the characters of wild animals and plants, as well as those of domesticated races, are inherited both in the wild and in domesticated forms according to the Mendel's Law". "Evolution has taken place by the incorporation into the race of those mutations that are beneficial to the life and reproduction of the organism". Injurious mutations have practically no chance of becoming established. Far from rejecting evolution, as the title of his 1916 book may suggest, Morgan, laid the foundation of the science of genetics. He also laid the theoretical foundation for the mechanism of evolution: natural selection. Heredity was a central plank of Darwin's theory of natural selection, but Darwin could not provide a working theory of heredity.
Darwinism ''Darwinism'' is a term used to describe a theory of biological evolution developed by the English naturalist Charles Darwin (1809–1882) and others. The theory states that all species of organisms arise and develop through the natural sel ...
could not progress without a correct theory of genetics. By creating that foundation, Morgan contributed to the neo-Darwinian synthesis, despite his criticism of Darwin at the beginning of his career. Much work on the Evolutionary Synthesis remained to be done.


Awards and honors

Morgan left an important legacy in genetics. Some of Morgan's students from Columbia and Caltech went on to win their own Nobel Prizes, including George Wells Beadle and
Hermann Joseph Muller Hermann Joseph Muller (December 21, 1890 – April 5, 1967) was an American geneticist who was awarded the 1946 Nobel Prize in Physiology or Medicine, "for the discovery that mutations can be induced by X-rays". Muller warned of long-term dang ...
. Nobel prize winner
Eric Kandel Eric Richard Kandel (; born Erich Richard Kandel, November 7, 1929) is an Austrian-born American medical doctor who specialized in psychiatry, a neuroscientist and a professor of biochemistry and biophysics at the College of Physicians and Surgeo ...
has written of Morgan, "Much as Darwin's insights into the evolution of animal species first gave coherence to nineteenth-century biology as a descriptive science, Morgan's findings about genes and their location on chromosomes helped transform biology into an experimental science." * Johns Hopkins awarded Morgan an honorary LL.D. and the University of Kentucky awarded him an honorary Ph.D. * He was elected
Member of the National Academy of Sciences Membership of the National Academy of Sciences is an award granted to scientists that the National Academy of Sciences (NAS) of the United States judges to have made “distinguished and continuing achievements in original research”. Membership ...
in 1909. * He was elected to the
American Philosophical Society The American Philosophical Society (APS) is an American scholarly organization and learned society founded in 1743 in Philadelphia that promotes knowledge in the humanities and natural sciences through research, professional meetings, publicat ...
in 1915. * He was a member of the American Association for Anatomy. * He was elected a
Foreign Member of the Royal Society Fellowship of the Royal Society (FRS, ForMemRS and HonFRS) is an award granted by the Fellows of the Royal Society of London to individuals who have made a "substantial contribution to the improvement of natural science, natural knowledge, incl ...
(ForMemRS) in 1919 * In 1924 Morgan received the
Darwin Medal The Darwin Medal is one of the medals awarded by the Royal Society for "distinction in evolution, biological diversity and developmental, population and organismal biology". In 1885, International Darwin Memorial Fund was transferred to the ...
. * He was elected to the
American Academy of Arts and Sciences The American Academy of Arts and Sciences (The Academy) is one of the oldest learned societies in the United States. It was founded in 1780 during the American Revolution by John Adams, John Hancock, James Bowdoin, Andrew Oliver, and other ...
in 1928. * The Thomas Hunt Morgan School of Biological Sciences at the University of Kentucky is named for him. * The
Genetics Society of America The Genetics Society of America (GSA) is a scholarly membership society of more than 5,500 genetics researchers and educators, established in 1931. The Society was formed from the reorganization of the Joint Genetics Sections of the American Soc ...
annually awards the
Thomas Hunt Morgan Medal The Thomas Hunt Morgan Medal is awarded by the Genetics Society of America (GSA) for lifetime contributions to the field of genetics. The medal is named after Thomas Hunt Morgan, the 1933 Nobel Prize winner, who received this award for his work w ...
, named in his honor, to one of its members who has made a significant contribution to the science of genetics. * Thomas Hunt Morgan's discovery was illustrated on a 1989 stamp issued in Sweden, showing the discoveries of eight Nobel Prize-winning geneticists. * A junior high school in the Shoreline School District was named for Morgan until 1986.


Personal life

On June 4, 1904, Morgan married Lillian Vaughan Sampson (1870–1952), who had entered graduate school in biology at Bryn Mawr the same year Morgan joined the faculty; she put aside her scientific work for 16 years of their marriage when they had four children. Later she contributed significantly to Morgan's ''Drosophila'' work. One of their four children (one boy and three girls) was Isabel Morgan (1911–1996) (Marr. Mountain), who became a
virologist Virology is the scientific study of biological viruses. It is a subfield of microbiology that focuses on their detection, structure, classification and evolution, their methods of infection and exploitation of host cells for reproduction, the ...
at Johns Hopkins, specializing in
polio Poliomyelitis ( ), commonly shortened to polio, is an infectious disease caused by the poliovirus. Approximately 75% of cases are asymptomatic; mild symptoms which can occur include sore throat and fever; in a proportion of cases more severe ...
research. Morgan was an atheist.


See also

* Mildred Hoge Richards, pupil


References


Further reading

* * * * * *


External links

* including the Nobel Lecture on June 4, 1934 ''The Relation of Genetics to Physiology and Medicine''
Thomas Hunt Morgan Biological Sciences Building at University of Kentucky



Thomas Hunt Morgan

Biographical Memoirs
of the
National Academy of Sciences The National Academy of Sciences (NAS) is a United States nonprofit, NGO, non-governmental organization. NAS is part of the National Academies of Sciences, Engineering, and Medicine, along with the National Academy of Engineering (NAE) and the ...
* * * * {{DEFAULTSORT:Morgan, Thomas Hunt 1866 births 1945 deaths American atheists American geneticists American Nobel laureates California Institute of Technology faculty Columbia University faculty Corresponding Members of the Russian Academy of Sciences (1917–1925) Corresponding Members of the USSR Academy of Sciences Foreign members of the Royal Society History of genetics Honorary members of the USSR Academy of Sciences Johns Hopkins University alumni Key family (Maryland) Members of the Lwów Scientific Society Members of the Pontifical Academy of Sciences Nobel laureates in Physiology or Medicine Presidents of the United States National Academy of Sciences Recipients of the Copley Medal University of Kentucky alumni Scientists from Lexington, Kentucky Writers from Lexington, Kentucky Members of the Royal Society of Sciences in Uppsala Thomas Hunt Members of the American Philosophical Society Presidents of the American Society of Naturalists