Gemmules
   HOME

TheInfoList



OR:

Pangenesis was
Charles Darwin Charles Robert Darwin ( ; 12 February 1809 – 19 April 1882) was an English Natural history#Before 1900, naturalist, geologist, and biologist, widely known for his contributions to evolutionary biology. His proposition that all speci ...
's hypothetical mechanism for
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 ...
, in which he proposed that each part of the body continually emitted its own type of small organic particles called gemmules that aggregated in the
gonad A gonad, sex gland, or reproductive gland is a Heterocrine gland, mixed gland and sex organ that produces the gametes and sex hormones of an organism. Female reproductive cells are egg cells, and male reproductive cells are sperm. The male gon ...
s, contributing heritable information to the
gamete A gamete ( ) is a Ploidy#Haploid and monoploid, haploid cell that fuses with another haploid cell during fertilization in organisms that Sexual reproduction, reproduce sexually. Gametes are an organism's reproductive cells, also referred to as s ...
s. He presented this 'provisional hypothesis' in his 1868 work ''
The Variation of Animals and Plants Under Domestication ''The Variation of Animals and Plants Under Domestication'' is a book by Charles Darwin that was first published in January 1868. A large proportion of the book contains detailed information on the domestication of animals and plants but it al ...
'', intending it to fill what he perceived as a major gap in evolutionary theory at the time. The etymology of the word comes from the
Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...
words ''pan'' (a prefix meaning "whole", "encompassing") and ''genesis'' ("birth") or ''genos'' ("origin"). Pangenesis mirrored ideas originally formulated by
Hippocrates Hippocrates of Kos (; ; ), also known as Hippocrates II, was a Greek physician and philosopher of the Classical Greece, classical period who is considered one of the most outstanding figures in the history of medicine. He is traditionally referr ...
and other pre-Darwinian scientists, but using new concepts such as
cell theory In biology, cell theory is a scientific theory first formulated in the mid-nineteenth century, that living organisms are made up of cells, that they are the basic structural/organizational unit of all organisms, and that all cells come from pr ...
, explaining cell development as beginning with gemmules which were specified to be necessary for the occurrence of new growths in an organism, both in initial development and regeneration. It also accounted for
regeneration Regeneration may refer to: Science and technology * Regeneration (biology), the ability to recreate lost or damaged cells, tissues, organs and limbs * Regeneration (ecology), the ability of ecosystems to regenerate biomass, using photosynthesis ...
and the
Lamarckian Lamarckism, also known as Lamarckian inheritance or neo-Lamarckism, is the notion that an organism can pass on to its offspring physical characteristics that the parent organism acquired through use or disuse during its lifetime. It is also calle ...
concept of the inheritance of acquired characteristics, as a body part altered by the environment would produce altered gemmules. This made Pangenesis popular among the neo-Lamarckian school of evolutionary thought. This hypothesis was made effectively obsolete after the 1900 rediscovery among
biologist A biologist is a scientist who conducts research in biology. Biologists are interested in studying life on Earth, whether it is an individual Cell (biology), cell, a multicellular organism, or a Community (ecology), community of Biological inter ...
s 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 ...
's theory of the particulate nature of inheritance.


Early history

Pangenesis was similar to ideas put forth by
Hippocrates Hippocrates of Kos (; ; ), also known as Hippocrates II, was a Greek physician and philosopher of the Classical Greece, classical period who is considered one of the most outstanding figures in the history of medicine. He is traditionally referr ...
,
Democritus Democritus (, ; , ''Dēmókritos'', meaning "chosen of the people"; – ) was an Ancient Greece, Ancient Greek Pre-Socratic philosophy, pre-Socratic philosopher from Abdera, Thrace, Abdera, primarily remembered today for his formulation of an ...
and other pre-Darwinian scientists in proposing that the whole of parental organisms participate in heredity (thus the prefix ''pan''). Darwin wrote that Hippocrates' pangenesis was "almost identical with mine—merely a change of terms—and an application of them to classes of facts necessarily unknown to the old philosopher."Deichmann, Ute. (2010). ''Darwinism, Philosophy, and Experimental Biology''. Springer. pp. 41-42. The historian of science
Conway Zirkle Conway Zirkle (October 28, 1895 – March 28, 1972) was an American botanist and historian of science. Zirkle was professor emeritus at the University of Pennsylvania. He was highly critical of Lamarckism, Lysenkoism, and Marxian biology.Jorav ...
wrote that: Zirkle demonstrated that the idea of inheritance of acquired characteristics had become fully accepted by the 16th century and remained immensely popular through to the time of Lamarck's work, at which point it began to draw more criticism due to lack of hard evidence. He also stated that pangenesis was the only scientific explanation ever offered for this concept, developing from Hippocrates' belief that "the semen was derived from the whole body." In the 13th century, pangenesis was commonly accepted on the principle that semen was a refined version of food unused by the body, which eventually translated to 15th and 16th century widespread use of pangenetic principles in medical literature, especially in gynecology. Later pre-Darwinian important applications of the idea included hypotheses about the origin of the differentiation of races. A theory put forth by
Pierre Louis Maupertuis Pierre Louis Moreau de Maupertuis (; ; 1698 – 27 July 1759) was a French mathematician, philosopher and man of letters. He became the director of the Académie des Sciences and the first president of the Prussian Academy of Science, at the ...
in 1745 called for particles from both parents governing the attributes of the child, although some historians have called his remarks on the subject cursory and vague. In 1749, the French naturalist
Georges-Louis Leclerc, Comte de Buffon Georges-Louis Leclerc, Comte de Buffon (; 7 September 1707 – 16 April 1788) was a French Natural history, naturalist, mathematician, and cosmology, cosmologist. He held the position of ''intendant'' (director) at the ''Jardin du Roi'', now ca ...
developed a hypothetical system of heredity much like Darwin's pangenesis, wherein 'organic molecules' were transferred to offspring during reproduction and stored in the body during development. Commenting on Buffon's views, Darwin stated, "If Buffon had assumed that his organic molecules had been formed by each separate unit throughout the body, his view and mine would have been very closely similar." In 1801,
Erasmus Darwin Erasmus Robert Darwin (12 December 173118 April 1802) was an English physician. One of the key thinkers of the Midlands Enlightenment, he was also a natural philosophy, natural philosopher, physiology, physiologist, Society for Effecting the ...
advocated a hypothesis of pangenesis in the third edition of his book ''
Zoonomia ''Zoonomia; or the Laws of Organic Life'' (1794–96) is a two-volume medical work by Erasmus Darwin dealing with pathology, anatomy, psychology, and the functioning of the body. Its primary framework is one of associationist psychophysiology ...
''. In 1809,
Jean-Baptiste Lamarck Jean-Baptiste Pierre Antoine de Monet, chevalier de Lamarck (1 August 1744 – 18 December 1829), often known simply as Lamarck (; ), was a French naturalist, biologist, academic, and soldier. He was an early proponent of the idea that biologi ...
in his '' Philosophie Zoologique'' put forth evidence for the idea that characteristics acquired during the lifetime of an organism, from either environmental or behavioural effects, may be passed on to the offspring. Charles Darwin first had significant contact with
Lamarckism Lamarckism, also known as Lamarckian inheritance or neo-Lamarckism, is the notion that an organism can pass on to its offspring physical characteristics that the parent organism acquired through use or disuse during its lifetime. It is also calle ...
during his time at the
University of Edinburgh Medical School The University of Edinburgh Medical School (also known as Edinburgh Medical School) is the medical school of the University of Edinburgh in Scotland and the United Kingdom and part of the University of Edinburgh College of Medicine and Veterinar ...
in the late 1820s, both through
Robert Edmond Grant Robert Edmond Grant MD FRCPEd FRS FRSE FZS FGS (11 November 1793 – 23 August 1874) was a British anatomist and zoologist. Life Grant was born at Argyll Square in Edinburgh (demolished to create Chambers Street), the son of Alexander Gra ...
, whom he assisted in research, and in Erasmus's journals. Darwin's first known writings on the topic of Lamarckian ideas as they related to inheritance are found in a notebook he opened in 1837, also entitled ''Zoonomia''. Historian Jonathan Hodge states that the theory of pangenesis itself first appeared in Darwin's notebooks in 1841. In 1861, the Irish physician Henry Freke developed a variant of pangenesis in his book ''Origin of Species by Means of Organic Affinity''. Freke proposed that all life was developed from microscopic organic agents which he named ''granules'', which existed as 'distinct species of organizing matter' and would develop into different biological structures. Four years before the publication of ''Variation'', in his 1864 book ''Principles of Biology'',
Herbert Spencer Herbert Spencer (27 April 1820 – 8 December 1903) was an English polymath active as a philosopher, psychologist, biologist, sociologist, and anthropologist. Spencer originated the expression "survival of the fittest", which he coined in '' ...
proposed a theory of "physiological units" similar to Darwin's gemmules, which likewise were said to be related to specific body parts and responsible for the transmission of characteristics of those body parts to offspring. He supported the
Lamarckian Lamarckism, also known as Lamarckian inheritance or neo-Lamarckism, is the notion that an organism can pass on to its offspring physical characteristics that the parent organism acquired through use or disuse during its lifetime. It is also calle ...
idea of transmission of acquired characteristics. Darwin had debated whether to publish a theory of heredity for an extended period of time due to its highly speculative nature. He decided to include pangenesis in ''Variation'' after sending a 30-page manuscript to his close friend and supporter
Thomas Huxley Thomas Henry Huxley (4 May 1825 – 29 June 1895) was an English biologist and anthropologist who specialized in comparative anatomy. He has become known as "Darwin's Bulldog" for his advocacy of Charles Darwin's theory of evolution. The stor ...
in May 1865, which was met by significant criticism from Huxley that made Darwin even more hesitant. However, Huxley eventually advised Darwin to publish, writing: "Somebody rummaging among your papers half a century hence will find Pangenesis & say 'See this wonderful anticipation of our modern Theories—and that stupid ass, Huxley, prevented his publishing them'" Darwin's initial version of pangenesis appeared in the first edition of ''Variation'' in 1868, and was later reworked for the publication of a second edition in 1875.


Theory


Darwin

Darwin's pangenesis theory attempted to explain the process of
sexual reproduction Sexual reproduction is a type of reproduction that involves a complex life cycle in which a gamete ( haploid reproductive cells, such as a sperm or egg cell) with a single set of chromosomes combines with another gamete to produce a zygote tha ...
, inheritance of traits, and complex
developmental Development of the human body is the process of growth to maturity. The process begins with fertilization, where an egg released from the ovary of a female is penetrated by a sperm cell from a male. The resulting zygote develops through mitosis ...
phenomena such as cellular
regeneration Regeneration may refer to: Science and technology * Regeneration (biology), the ability to recreate lost or damaged cells, tissues, organs and limbs * Regeneration (ecology), the ability of ecosystems to regenerate biomass, using photosynthesis ...
in a unified mechanistic structure. Longshan Liu wrote that in modern terms, pangenesis deals with issues of "dominance inheritance, graft hybridization, reversion, xenia,
telegony The ''Telegony'' () is a lost epic poem of Ancient Greek literature. It is named after Telegonus, the son of Odysseus by Circe, whose name ("born far away") is indicative of his birth on Aeaea, far from Odysseus' home of Ithaca. It was part o ...
, the inheritance of acquired characters, regeneration and many groups of facts pertaining to variation, inheritance and development." Mechanistically, Darwin proposed pangenesis to occur through the transfer of organic particles which he named 'gemmules.' Gemmules, which he also sometimes referred to as '','' pangenes, granules, or germs, were supposed to be shed by the organs of the body and carried in the bloodstream to the reproductive organs where they accumulated in the germ cells or gametes. Their accumulation was thought to occur by some sort of a 'mutual affinity.' Each gemmule was said to be specifically related to a certain body part- as described, they did not contain information about the entire organism. The different types were assumed to be dispersed through the whole body, and capable of self-replication given 'proper nutriment'. When passed on to offspring via the reproductive process, gemmules were thought to be responsible for developing into each part of an organism and expressing characteristics inherited from both parents. Darwin thought this to occur in a literal sense: he explained cell proliferation to progress as gemmules to bind to more developed cells of their same character and mature. In this sense, the uniqueness of each individual would be due to their unique mixture of their parents' gemmules, and therefore characters. Similarity to one parent over the other could be explained by a quantitative superiority of one parent's gemmules. Yongshen Lu points out that Darwin knew of cells' ability to multiply by self-division, so it is unclear how Darwin supposed the two proliferation mechanisms to relate to each other. He did clarify in a later statement that he had always supposed gemmules to only bind to and proliferate from developing cells, not mature ones. Darwin hypothesized that gemmules might be able to survive and multiply outside of the body in a letter to
J. D. Hooker Sir Joseph Dalton Hooker (30 June 1817 – 10 December 1911) was a British botanist and explorer in the 19th century. He was a founder of geographical botany and Charles Darwin's closest friend. For 20 years he served as director of the Ro ...
in 1870. Some gemmules were thought to remain dormant for generations, whereas others were routinely expressed by all offspring. Every child was built up from selective expression of the mixture of the parents and grandparents' gemmules coming from either side. Darwin likened this to gardening: a flowerbed could be sprinkled with seeds "most of which soon germinate, some lie for a period dormant, whilst others perish." He did not claim gemmules were in the blood, although his theory was often interpreted in this way. Responding to Fleming Jenkin's review of ''
On the Origin of Species ''On the Origin of Species'' (or, more completely, ''On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life'')The book's full original title was ''On the Origin of Species by M ...
'', he argued that pangenesis would permit the preservation of some favourable variations in a population so that they wouldn't die out through blending. Darwin thought that environmental effects that caused altered characteristics would lead to altered gemmules for the affected body part. The altered gemmules would then have a chance of being transferred to offspring, since they were assumed to be produced throughout an organism's life. Thus, pangenesis theory allowed for the Lamarckian idea of transmission of characteristics acquired through use and disuse. Accidental gemmule development in incorrect parts of the body could explain deformations and the 'monstrosities' Darwin cited in ''Variation''.


De Vries

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 ...
characterized his own version of pangenesis theory in his 1889 book ''Intracellular Pangenesis'' with two propositions, of which he only accepted the first: :I. In the cells there are numberless particles which differ from each other, and represent the individual cells, organs, functions and qualities of the whole individual. These particles are much larger than the chemical molecules and smaller than the smallest known organisms; yet they are for the most part comparable to the latter, because, like them, they can divide and multiply through nutrition and growth. They are transmitted, during cell-division, to the daughter-cells: this is the ordinary process of heredity. :II. In addition to this, the cells of the organism, at every stage of development, throw off such particles, which are conducted to the germ-cells and transmit to them those characters which the respective cells may have acquired during development.


Other variants

The historian of science
Janet Browne Elizabeth Janet Browne (née Bell, born 30 March 1950) is a British historian of science, known especially for her work on the history of 19th-century biology. She taught at the Wellcome Trust Centre for the History of Medicine, University Coll ...
points out that while Spencer and
Carl von Nägeli Carl may refer to: *Carl, Georgia, city in USA *Carl, West Virginia, an unincorporated community *Carl (name), includes info about the name, variations of the name, and a list of people with the name *Carl², a TV series * "Carl", an episode of tel ...
also put forth ideas for systems of inheritance involving gemmules, their version of gemmules differed from Darwin's in that it contained "a complete microscopic blueprint for an entire creature." Spencer published his theory of "physiological units" three years prior to Darwin's publication of ''Variation''. Browne adds that Darwin believed specifically in gemmules from each body part because they might explain how environmental effects could be passed on as characteristics to offspring. Interpretations and applications of pangenesis continued to appear frequently in medical literature up until Weismann's experiments and subsequent publication on germ-plasm theory in 1892. For instance, an address by Huxley spurred on substantial work by Dr. James Ross in linking ideas found in Darwin's pangenesis to the
germ theory of disease The germ theory of disease is the currently accepted scientific theory for many diseases. It states that microorganisms known as pathogens or "germs" can cause disease. These small organisms, which are too small to be seen without magnification, ...
. Ross cites the work of both Darwin and Spencer as key to his application of pangenetic theory.


Collapse


Galton's experiments on rabbits

Darwin's half-cousin
Francis Galton Sir Francis Galton (; 16 February 1822 – 17 January 1911) was an English polymath and the originator of eugenics during the Victorian era; his ideas later became the basis of behavioural genetics. Galton produced over 340 papers and b ...
conducted wide-ranging inquiries into heredity which led him to refute Charles Darwin's hypothetical theory of pangenesis. In consultation with Darwin, he set out to see if gemmules were transported in the blood. In a long series of experiments from 1869 to 1871, he transfused the blood between dissimilar breeds of rabbits, and examined the features of their offspring. He found no evidence of characters transmitted in the transfused blood.
Galton Sir Francis Galton (; 16 February 1822 – 17 January 1911) was an English polymath and the originator of eugenics during the Victorian era; his ideas later became the basis of behavioural genetics. Galton produced over 340 papers and b ...
was troubled because he began the work in good faith, intending to prove Darwin right, and having praised pangenesis in ''Hereditary Genius'' in 1869. Cautiously, he criticized his cousin's theory, although qualifying his remarks by saying that Darwin's gemmules, which he called "pangenes", might be temporary inhabitants of the blood that his experiments had failed to pick up. Darwin challenged the validity of Galton's experiment, giving his reasons in an article published in ''Nature'' where he wrote: After the circulation of Galton's results, the perception of pangenesis quickly changed to severe skepticism if not outright disbelief.


Weismann

August Weismann August Friedrich Leopold Weismann (; 17 January 18345 November 1914) was a German evolutionary biology, evolutionary biologist. Fellow German Ernst Mayr ranked him as the second most notable evolutionary theorist of the 19th century, after Charl ...
's idea, set out in his 1892 book ''Das Keimplasma: eine Theorie der Vererbung'' (The Germ Plasm: a Theory of Inheritance), was that the hereditary material, which he called the
germ plasm Germ plasm () is a biological concept developed in the 19th century by the German biologist August Weismann. It states that heritable information is transmitted only by germ cells in the gonads (ovaries and testes), not by somatic cells. The ...
, and the rest of the body (the
soma Soma may refer to: Businesses and brands * SOMA (architects), a New York–based firm of architects * Soma (company), a company that designs eco-friendly water filtration systems * SOMA Fabrications, a builder of bicycle frames and other bicycle ...
) had a one-way relationship: the germ-plasm formed the body, but the body did not influence the germ-plasm, except indirectly in its participation in a population subject to natural selection. This distinction is commonly referred to as the
Weismann Barrier The Weismann barrier, proposed by August Weismann, is the strict distinction between the "immortal" germ cell lineages producing gametes and "disposable" somatic cells in animals (but not plants), in contrast to Charles Darwin's proposed pangenesi ...
. If correct, this made Darwin's pangenesis wrong and Lamarckian inheritance impossible. His experiment on mice, cutting off their tails and showing that their offspring had normal tails across multiple generations, was proposed as a proof of the non-existence of Lamarckian inheritance, although Peter Gauthier has argued that Weismann's experiment showed only that injury did not affect the germ plasm and neglected to test the effect of Lamarckian use and disuse. Weismann argued strongly and dogmatically for Darwinism and against neo-Lamarckism, polarising opinions among other scientists. This increased anti-Darwinian feeling, contributing to its eclipse.


After pangenesis

Darwin's pangenesis theory was widely criticised, in part for its
Lamarckian Lamarckism, also known as Lamarckian inheritance or neo-Lamarckism, is the notion that an organism can pass on to its offspring physical characteristics that the parent organism acquired through use or disuse during its lifetime. It is also calle ...
premise that parents could pass on traits acquired in their lifetime. Conversely, the neo-Lamarckians of the time seized upon pangenesis as evidence to support their case. Italian Botanist Federico Delpino's objection that gemmules' ability to self-divide is contrary to their supposedly innate nature gained considerable traction; however, Darwin was dismissive of this criticism, remarking that the particulate agents of smallpox and scarlet fever seem to have such characteristics. Lamarckism fell from favour after
August Weismann August Friedrich Leopold Weismann (; 17 January 18345 November 1914) was a German evolutionary biology, evolutionary biologist. Fellow German Ernst Mayr ranked him as the second most notable evolutionary theorist of the 19th century, after Charl ...
's research in the 1880s indicated that changes from use (such as lifting weights to increase muscle mass) and disuse (such as being lazy and becoming weak) were not heritable. However, some scientists continued to voice their support in spite of Galton's and Weismann's results: notably, in 1900 Karl Pearson wrote that pangenesis "is no more disproved by the statement that 'gemmules have not been found in the blood,' than the atomic theory is disproved by the fact that no atoms have been found in the air." Finally, the rediscovery of Mendel's Laws of Inheritance in 1900 led to pangenesis being fully set aside. Julian Huxley has observed that the later discovery of
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 the research of T. H. Morgan also made pangenesis untenable. Some of Darwin's pangenesis principles do relate to heritable aspects of
phenotypic plasticity Phenotypic plasticity refers to some of the changes in an organism's behavior, morphology and physiology in response to a unique environment. Fundamental to the way in which organisms cope with environmental variation, phenotypic plasticity encompa ...
, although the status of gemmules as a distinct class of organic particles has been firmly rejected. However, starting in the 1950s, many research groups in revisiting Galton's experiments found that heritable characteristics could indeed arise in rabbits and chickens following DNA injection or blood transfusion. This type of research originated in the Soviet Union in the late 1940s in the work of Sopikov and others, and was later corroborated by researchers in Switzerland as it was being further developed by the Soviet scientists. Notably, this work was supported in the USSR in part due to its conformation with the ideas of
Trofim Lysenko Trofim Denisovich Lysenko (; , ; 20 November 1976) was a Soviet agronomist and scientist.''An ill-educated agronomist with huge ambitions, Lysenko failed to become a real scientist, but greatly succeeded in exposing of the “bourgeois enemies o ...
, who espoused a version of neo-Lamarckism as part of
Lysenkoism Lysenkoism ( ; ) was a political campaign led by the Soviet biologist Trofim Lysenko against genetics and science-based agriculture in the mid-20th century, rejecting natural selection in favour of a form of Lamarckism, as well as expanding upon ...
. Further research of this heritability of acquired characteristics developed into, in part, the modern field of
epigenetics 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 ...
. Darwin himself had noted that "the existence of free gemmules is a gratuitous assumption"; by some accounts in modern interpretation, gemmules may be considered a prescient mix of DNA, RNA, proteins, prions, and other mobile elements that are heritable in a non-Mendelian manner at the molecular level. Liu points out that Darwin's ideas about gemmules replicating outside of the body are predictive of ''in vitro'' gene replication used, for instance, in PCR.


See also

*
Modern synthesis Modern synthesis or modern evolutionary synthesis refers to several perspectives on evolutionary biology, namely: * Modern synthesis (20th century), the term coined by Julian Huxley in 1942 to denote the synthesis between Mendelian genetics and s ...


References


External links


On-line Facsimile Edition of ''The Variation of Animals and Plants Under Domestication''
from Electronic Scholarly Publishing

From: Freeman, R. B. 1977. ''The Works of Charles Darwin: An Annotated Bibliographical Handlist''. 2nd edn. Dawson: Folkestone, at DarwinOnline, with links to online versions of the 1st. edition, first and second issues, and the 2nd. edition. {{Charles Darwin Charles Darwin Developmental biology Evolutionary biology History of biology History of genetics Obsolete biology theories Lamarckism