Theory Of Pangenesis Research Articles

Epididymosomes: the black box of Darwin's pangenesis?

Darwin, in the pangenesis theory, imagined particles, named as 'gemmules', which are released from all ('pan') cells of the body. By cell-cell communication and also circulation through the body, they finally reach the germ cells to participate in the generation ('genesis') of the new individual. It has been shown that circulatory exosomes are affected by environmental stressors and they can reach the parental germ cells. Therefore, in the mirror of his theory, circulatory exosomes could interact with epididymosomes: epididymis-derived exosomes which have a wide spectrum of variation in content and size, are very sensitive to environmental stressors, and may be involved in translating external information to the germ cells. The protein and RNA cargo would be transferred by epididymosomes to sperm during sperm maturation, which would be then delivered to the embryo at fertilization and inherited by offspring. Therefore, in this study, we will briefly discuss Darwin's pangenesis theory and its possible relation with epididymosomes. We believed that epididymosomes could be considered as an attractive candidate for the storage of RNA contents, changing the epigenome of the next generations, and allowing the reappearance acquired characteristics of ancestors. Therefore, epididymosomes, as a black box of Darwin's pangenesis, may unravel parental life history and also disclose the historical events that affect the life of offspring.

150 years of Darwin's theory of intercellular flow of hereditary information.

Charles Darwin's Pangenesis theory, which proposed an intercellular mechanism for the flow of hereditary information, is gaining new ground.

Evolvability of Amyloidogenic Proteins in Human Brain.

Currently, the physiological roles of amyloidogenic proteins (APs) in human brain, such as amyloid-β and α-synuclein, are elusive. Given that many APs arose by gene duplication and have been resistant against the pressures of natural selection, APs may be associated with some functions that are advantageous for survival of offspring. Nonetheless, evolvability is the sole physiological quality of APs that has been characterized in microorganisms such as yeast. Since yeast and human brain may share similar strategies in coping with diverse range of critical environmental stresses, the objective of this paper was to discuss the potential role of evolvability of APs in aging-associated neurodegenerative disorders, including Alzheimer’s disease and Parkinson’s disease. Given the heterogeneity of APs in terms of structure and cytotoxicity, it is argued that APs might be involved in preconditioning against diverse stresses in human brain. It is further speculated that these stress-related APs, most likely protofibrillar forms, might be transmitted to offspring via the germline, conferring preconditioning against forthcoming stresses. Thus, APs might represent a vehicle for the inheritance of the acquired characteristics against environmental stresses. Curiously, such a characteristic of APs is reminiscent of Charles Darwin’s ‘gemmules’, imagined molecules of heritability described in his pangenesis theory. We propose that evolvability might be a physiological function of APs during the reproductive stage and neurodegenerative diseases could be a by-product effect manifested later in aging. Collectively, our evolvability hypothesis may play a complementary role in the pathophysiology of APs with the conventional amyloid cascade hypothesis.

Pangenesis, genes, epigenesis

In 1868, Darwin published his book The variation of animals and plants under domestication, which laid out his theory of heredity. This included the assumption that development was essential to understanding the evolutionary process. This present article reassesses the Darwinian theory of pangenesis in order to revisit its historical value. The conclusion is that the theory of pangenesis was well-suited to its time, and additionally, reflections of this assumption can be found in work in new areas known as evolutionary biology of development (evo-devo) and epigenetics.

The Fertile Darwins: Epigenesis, Organicism, and the Problem of Inheritance

This essay explores the Darwinian imagination – an approach to exploring the basic ontology of nature that was shared by both Erasmus Darwin and his grandson, Charles Darwin. It focuses on Erasmus and Charles’s respective theories of generation, especially as laid out in Zoonomia (1794) and The Variation of Animals and Plants Under Domestication (1868), and their derivation from the longstanding opposition between theories of epigenesis and panspermia. Erasmus Darwin’s thinking, in particular, was torn between relatively closed and open conceptions of how organic structures assemble and reproduce. Charles, by contrast, worked hard to fashion his theory of pangenesis into a capacious model that would account for interactions of inheritance and development across all levels of physical and temporal scale. Yet beneath disagreements over the distribution of agency between matter and different sexual partners, both argued for an anti-holist, anti-organic ontology that consistently cleared space for more open, more contingent, and ultimately more ecological theories of nature. Ultimately this required a rejection both of the Romantic conception of organic life and Romantic aesthetics, in particular, the notion that the unity of aesthetic experience communicated something about the unity of natural systems. Finally, I will argue that Charles Darwin’s pangenic model – which relies upon the functional assemblage of elements derived from different lineages, on different timescales, and with distinct, non-overlapping, and incompletely integrated capacities – offers a unique way of understanding the problem of intellectual inheritance and the relation between the Darwins themselves. If most approaches to this problem have posited either a lineal genealogy of intellectual inheritance, or situated their work as reflections of a larger historical context, pangenesis can help to imagine intellectual history beyond our typically lineal or atmospheric models of influence.

William Keith Brooks and the naturalist's defense of Darwinism in the late-nineteenth century.

William Keith Brooks was an American zoologist at Johns Hopkins University from 1876 until his death in 1908. Over the course of his career, Brooks staunchly defended Darwinism, arguing for the centrality of natural selection in evolutionary theory at a time when alternative theories, such as neo-Lamarckism, grew prominent in American biology. In his book The Law of Heredity (1883), Brooks addressed problems raised by Darwin's theory of pangenesis. In modifying and developing Darwin's pangenesis, Brooks proposed a new theory of heredity that sought to avoid the pitfalls of Darwin's hypothesis. In so doing he strengthened Darwin's theory of natural selection by undermining arguments for the inheritance of acquired characteristics. In later attacks on neo-Lamarckism, Brooks consistently defended Darwin's theory of natural selection on logical grounds, continued to challenge the idea of the inheritance of acquired characteristics, and argued that natural selection best explained a wide range of adaptations. Finally, he critiqued Galton's statistical view of heredity and argued that Galton had resurrected an outmoded typological concept of species, one which Darwin and other naturalists had shown to be incorrect. Brooks's ideas resemble the "biological species concept" of the twentieth century, as developed by evolutionary biologist Ernst Mayr and others. The late-nineteenth century was not a period of total "eclipse" of Darwinism, as biologists and historians have hitherto seen it. Although the "Modern Synthesis" refers to the reconciliation of post-Mendelian genetics with evolution by natural selection, we might adjust our understanding of how the synthesis developed by seeing it as the culmination of a longer discussion that extends back to the late-nineteenth century.

The concept of the causal role of chromosomes and genes in heredity and development: opponents from Darwin to Lysenko.

The idea of chromosomes and genes as causal agents in development and heredity originated in late 19th-century cytology, and it was most strongly supported by Theodor Boveri and Edmund B. Wilson. The concept of genes, which was central and most fruitful in classical genetics, appeared, however, unappealing and insufficient to many for explaining complex biological phenomena such as development.Philosophical outlooks, among them "Lamarckian" and holistic predilections, played a significant role in scientists' objection to genes as causal factors. A wide conceptual gap between genetics and developmental biology ensued. The strongest attack on the concept of genes was launched by agronomist and politician Trofim Lysenko in the Soviet Union under Stalin. Brushing aside the "Mendelist-Morganist" methods of classical genetics, Lysenko put forward a holistic concept of heredity that incorporated development and heritable responses to environmental conditions, similar to Darwin's Pangenesis theory, though of course some 60 years later. Recent developments include the role of genes in research on epigenetic marks and in systems approaches based on embryological gene regulatory networks.

Commentary: Wilhelm Johannsen and the problem of heredity at the turn of the 19th century

Darwin’s theory of the origin of species by means of natural selection was essentially dependent on his views about inheritance. The character had to be inherited, to some extent at least, if the mechanism of natural selection was to produce evolutionary changes. Only hereditary variability would work. But Darwin’s theory of heredity was primitive. As the Danish plant physiologist Wilhelm Johannsen wrote, Darwin’s theory of pangenesis was more or less the same as that which Hippocrates had held 22 centuries earlier [p. 54].1 With the cytological discoveries of the late 19th century, and the efforts to give plant and animal breeding a scientific basis, a new era began. Botanists and plant breeders in particular played a central role in the decades around 1900, when the founding of genetics took place. The chromosome theory as outlined by Thomas Hunt Morgan and his co-workers in The Mechanism of Mendelian Heredity2 was a major benchmark in the early history of genetics. It can be seen as setting the course that led to the discovery of DNA structure and the beginnings of molecular genetics four decades later. It is worth asking if similar status should be given to Johannsen’s 1910 lecture on ‘The genotype conception of heredity’.3 This lecture summed up his experimental and theoretical achievements, including a sharp analysis of the concepts of ‘genotype’ and ‘gene’. He had himself coined these terms two years earlier in his magisterial textbook Elemente der Exakten Erblichkeitslehre (Elements of an Exact Theory of Heredity).4 Genotype is the basic concept in Johannsen’s 1910 lecture. The stability of the genotype is what makes a science of heredity possible. The concept of ‘gene’ is derivative. It represents an experimentally identifiable difference between genotypes. From this holistic perspective he developed his criticism of the particulate gene concept that became the basis of mid-20th century Neo-Darwinism, the ‘New Synthesis’ of genetics and evolution. Johannsen in his later writings praised highly the discoveries of Drosophila genetics as fundamental novelties5 (consecutive editions were extensively reworked and thus demonstrate both the continuity and the change in Johannsen’s genotype theory), but still insisted that there was more to heredity and to the explanation of evolution than could be explained by such particulate genes.6,7

Shopping for answers from Marx and Spencer

Shopping for answers from Marx and Spencer

The development of Francis Galton's ideas on the mechanism of heredity.

Galton greeted Darwin's theory of pangenesis with enthusiasm, and tried to test the assumption that the heredity particles circulate in the blood by transfusion experiments on rabbits. The failure of these experiments led him to reject this assumption, and in the 1870s he developed an alternative theory of heredity, which incorporated those parts of Darwin's theory that did not involve the transportation of hereditary particles throughout the system. He supposed that the fertilized ovum contains a large number of hereditary elements, which he collectively called the "stirp," a few of which are patent, developing into particular cell types, while the rest remain latent; the latent elements can be transmitted to the next generation, while the patent elements, with rare exceptions, cannot since they have developed into cells. The problem with this theory is that it does not explain the similarity between parent and child unless there is a high correlation between latent and patent elements. Galton probably came to realize this problem during his subsequent statistical work on heredity, and he quietly dropped the idea that patent elements are not transmitted in Natural Inheritance (1889). Galton thought that brothers and sisters had identical stirps, and he attributed differences between them to variability in the choice of patent elements from the stirp, that is to say to developmental variability. He attributed the likeness of monozygotic twins to the similarity of their developmental environment. Galton's twin method was to track the life history changes of twins to see whether twins who were similar at birth diverged in dissimilar environments or whether twins who were dissimilar at birth converged in similar environments. It is quite different from the modern twin method of comparing the similarities between monozygotic and dizygotic twins, on the assumption that monozygotic twins are genetically identical whereas dizygotic twins are not. It has been argued that Galton foreshadowed Weismann's theory in the continuity of the germ-plasm, but this is only true in a weak sense. They both believed that the inheritance of acquired characters was either rare or impossible, but Galton did not forestall the essential part of Weismann's theory, that the germ-plasm of the zygote is doubled, with one part being reserved for the formation of the germ-cells.

A Darwinian Statement of the Mendelian Theory

So far as the present writer knows, no public notice has yet been given to a series of statements by Darwin in his “Animals and Plants under Domestication” that constitute virtually a statement of the Mendelian theory of the distribution and recombination of factors in hybrid offspring. Darwin's idea of dissociation is, of course, founded on Naudin's conception of disjunction; but the remainder of his theory is as original as Mendel's, except that it is purely speculative instead of being derived directly from experimental data. It is worked out, as a matter of fact, by means of his theory of pangenesis.

Perigenesis v. Pangenesis—Haeckel's New Theory of Heredity

UNDER the title “Perigenesis der Plastidule oder die Wellenzeugung der Lebenstheilchen,” Prof. Haeckel has published quite recently a pamphlet containing an attempt to furnish a mechanical explanation of the elementary phenomena of reproduction which shall be more satisfactory than Mr. Darwin's ingenious and well-known theory of Pangenesis. I shall endeavour to show that Prof. Haeckel's theory is essentially that with which both English and German students of Mr. Herbert Spencer's works have long been familiar; and that it does not furnish a clearer explanation than does Mr. Darwin's Pangenesis, of the special facts of heredity which Mr. Darwin had in view.

Pangenesis: Graft-Hybrids

IN your last number Mr. Ranyard brings forward an objection to Mr. Darwin's theory of Pangenesis on the ground that the grafting of a bud on a stock of a different species does not produce a hybrid offspring. I am not about to defend the doctrine of Pangenesis, which appears to me incapable alike of proof and of disproof. It is, however, a well-known fact that the siock does affect the scion, and vice versâ. In Prof. Henfrey's “Elementary Course of Botany” (Dr. Masters's edition) he says, “A certain amount of physiological influence of the stock over the scion is shown to exist by such facts of horticultural experience as that the fruit of the pear is smaller and more highly coloured when ‘worked on’ the quince and medlar than when grafted on pear-stocks, and is earlier when worked on the mountain-ash.” The well-known instances of the communication of variegation from the scion to the stock in Abutilon, recorded by Prof. Moiren and others, are considered cases of contagious disease; but what is the theory ot contagion but that the blood or other “fluid” of an animal or plant is affected by emanations call them “gemmules” or what you will, from another individual? The same writer records an instance which he considers well authenticated of the production of the hybrid Cytisus Adami by the grafting of C. purpureus on C. laburnum.

Pangenesis

DOUBTLESS it is owing to a slight misprint in my communication in your number of May 11 that your correspondent, Mr. Meldola, has mistaken the gist of my objection to the theory of Pangenesis. I wrote, “a seed borne upon the graft would certainly be affected by the gemmules arising in the root and stem of the stock;” this was printed “a bud borne,” &c. Now although it seems to me that much has been done to show that the stock will occasionally affect parts of the scion—and this my former letter does not for a moment contest—no evidence whatever has been brought to show that the sexual elements produced upon the scion have ever been affected by the stock without any intermediate change in the parts of the scion which may have borne the affected pollen grains or ovules.* And this certainly ought to be shown before it is assumed that every bud and every sexual element is formed by the aggregation of gemmules from all parts of the parents. Instead of which, in the vast majority of instances, we know that seeds borne upon the scion spring true to the scion. And if any instances to the contrary could be shown, it would then have to be proved that the part of the scion that bore the reproductive element was not a graft-hybrid. I may especially refer your readers to an interesting article by Dr. Masters, in the Popular Science Review for April, on “Grafting, its consequencs and effects.”