Darwin and Mendel: who was the pioneer of genetics?

Although Mendel is now widely recognized as the founder of genetics, historical studies have shown that he did not in fact propose the modern concept of paired characters linked to genes, nor did he formulate the two "Mendelian laws" in the form now given. Furthermore, Mendel was accused of falsifying his data, and Mendelism has been met with scepticism because of its failure to provide scientific explanation for evolution, to furnish a basis for the process of genetic assimilation and to explain the inheritance of acquired characters, graft hybridization and many other facts. Darwin was the first to clearly describe almost all genetical phenomena of fundamental importance, and was the first to present a developmental theory of heredity--Pangenesis, which not only greatly influenced many subsequent theories of inheritance, particularly those of de Vries, Galton, Brooks and Weismann, but also tied all aspects of variation, heredity and development together, provided a mechanism for most of the observable facts, and is supported by increasing evidence. It has also been indicated that Darwin's influence on Mendel, primarily from The Origin, is evident. The word "gene" was derived from "pangen", itself a derivative of "Pangenesis" which Darwin had coined. It seems that Darwin should have been regarded as the pioneer, if not of transmissional genetics, of developmental genetics and molecular genetics.     

Role of de Vries in the recovery of Mendel's work. I. Was de Vries really an independent discoverer of Mendel?

Recently, doubt has been cast on the view that de Vries developed the idea of disjunction independently of Mendel. Arguments are based on de Vries' own writings that showed the F2 data of his numerous crosses are reported as 3:1 ratios only after 1900. They also show that his theory of inheritance becomes quasi Mendelian only after 1900. The authors of this review paper cannot but agree with de Vries' critics that he did not develop his law of disjunction independently of Mendel. They also raise some questions that, hopefully, will lead to a reanalysis of de Vries' theory of inheritance in 1900.     

Fisher's contributions to genetics and heredity, with special emphasis on the Gregor Mendel controversy

R. A. Fisher is widely respected for his contributions to both statistics and genetics. For instance, his 1930 text on The Genetical Theory of Natural Selection remains a watershed contribution in that area. Fisher's subsequent research led him to study the work of (Johann) Gregor Mendel, the 19th century monk who first developed the basic principles of heredity with experiments on garden peas. In examining Mendel's original 1865 article, Fisher noted that the conformity between Mendel's reported and proposed (theoretical) ratios of segregating individuals was unusually good, "too good" perhaps. The resulting controversy as to whether Mendel "cooked" his data for presentation has continued to the current day. This review highlights Fisher's most salient points as regards Mendel's "too good" fit, within the context of Fisher's extensive contributions to the development of genetical and evolutionary theory.     

Mendel's experiments: A reinterpretation

Conclusion My conclusion is that Mendel deliberately, though without any real falsification, tried to suggest to his audience and readers an unlikely and substantially wrong reconstruction of the first and most important phase of his research. In my book I offer many reasons for this strange and surprising behavior,⁵³ but the main argument rests on the fact of linkage. Mendelian genetics cannot account for linkage because it was based on the idea of applying probability theory to the problem of species evolution. Central to the theory is the law of probability according to which the chance occurrence of a combination of independent events is the product of their separate probabilities. This is the common basis of Mendel's first and second laws, but this is why Mendel's second law on independent assortment is enunciated in too general a way. From Morgan's work we now know that characters may not always be independent if their genes are located very close one to the other on the same chromosome. And this was also the basis of Mendel's personal drama: he surely observed the effects of linkage, but he had no theoretical tools with which to explain it. So he presented his results in a logical structure consistent with the central idea of his theory. Had he described the real course of his experiments he would have had to admit that his law worked for only a few of the hundreds of Pisum characters — and it would thus have been considered more of an exception than a rule. This is why he insisted on the necessity of testing the law on other plants, and this is why in his second letter to Carl Nägeli he admits that the publication of his data was untimely and dangerous.⁵⁴.We can argue that already in 1866 Mendel was less confident that his so-called second law had the same general validity as the first — and that later he lost his confidence altogether. Contemporary testimony indicates that in the end he became as skeptical as all his contemporaries as to the scientific relevance of his theory.⁵⁵ But he was wrong. His research is in no way the fruit of methodological mistakes or forgery, and it remains a landmark in the history of science. He was only the victim of a strange destiny in which the use of probability theory was responsible, at the same time, for the strength and for the weakness of his theory. We must still consider him the father and founder of genetics.     

Role of de Vries in the rediscovery of Mendel's paper. II. Did de Vries really understand Mendel's paper?

In this paper, we discuss briefly three of the several lines of evidence that we believe demonstrate de Vries's lack of understanding of Mendel's paper. In our view, at least part of de Vries's failure of understanding derives from the fact that he appears to have viewed Mendel's paper as being mainly about the inheritance of characters that was his own interest. Therefore, he looked at it to see whether Mendel had found any laws of inheritance. Mendel had done his research for another purpose, to find the laws describing the formation of hybrids and the development of their offspring. Thus, de Vries started his examination of Mendel's paper with a very fundamental misunderstanding of what it was about.     

Gregor Mendel's classic paper and the nature of science in genetics courses

The discoveries of Gregor Mendel, as described by Mendel in his 1866 paper Versuche uber Pflanzen-Hybriden (Experiments on plant hybrids), can be used in undergraduate genetics and biology courses to engage students about specific nature of science characteristics and their relationship to four of his major contributions to genetics. The use of primary source literature as an instructional tool to enhance genetics students' understanding of the nature of science helps students more clearly understand how scientists work and how the science of genetics has evolved as a discipline. We offer a historical background of how the nature of science developed as a concept and show how Mendel's investigations of heredity can enrich biology and genetics courses by exemplifying the nature of science.     

Mendelian inheritance in Germany between 1900 and 1910. The case of Carl Correns (1864-1933)

Carl Correns (1864-1933) came to recognize Mendel's rules between 1894 and 1900 while trying to find out the mechanism of xenia, that is, the direct influence of the fertilizing pollen on the mother plant in maize and peas among other species. In this paper, I am concerned with the ten years of Correns' work after the annus mirabilis of 1900 until 1910, when the main outlines of the new science of genetics had been established. It is generally assumed that after 1900 Correns quickly began probing the limits of Mendelian inheritance, both as far as the explanatory force of formal transmission genetics and the generality of Mendel's laws are concerned. A careful examination of his papers however shows that he was much more interested in the scope of Mendelian inheritance than in its limits. Even his work with variegated Mirabilis plants, which historiographical folklore still presents as a result of Correns' growing interest in cytoplasmic inheritance, can be shown to have been conducted to corroborate just the opposite, namely, the validity of the nuclear paradigm. The paper will show that Correns' research results in those years (among them the Mendelian inheritance of sex in higher plants) were the outcome of a complex experimental program which involved breeding experiments with dozens of different species.     

William Bateson: a biologist ahead of his time

William Bateson coined the term genetics and, more than anybody else, championed the principles of heredity discovered by Gregor Mendel. Nevertheless, his reputation is soured by the positions he took about the discontinuities in inheritance that might precede formation of a new species and by his reluctance to accept, in its fullblooded form, the view of chromosomes as the controllers of individual development. Growing evidence suggests that both of these positions have been vindicated. New species are now thought to arise as the result of genetic interactions, chromosomal rearrangements, or both, that render hybrids less viable or sterile. Chromosomes are the sites of genes but genes move between chromosomes much more readily than had been previously believed and chromosomes are not causal in individual development. Development, like speciation, requires an understanding of the interactions between genes and the interplay between the individual and its environment.     

‘Further Development’ of Mendel’s legacy? Erich von Tschermak-Seysenegg in the context of Mendelian–biometry controversy, 1901–1906

The contribution of Erich von Tschermak-Seysenegg (1871?C1962) to the beginning of classical genetics is a matter of dispute. The aim of this study is to analyse, based on newly accessible archive materials, the relevance of his positions and theoretical views in a debate between advocates of early Mendelian explanation of heredity and proponents of biometry, which took place in England around 1901?C1906. We challenge not only his role of an ??external consultant??, which at the time de facto confirmed his status of ??rediscoverer?? of Mendel??s work but also analyse his ambivalent positions which are to be seen as a part of ??further development?? (Weiterführung), a development of Mendel??s legacy as he understood it. Second, there is an interesting aspect of establishing connections within an ??experimental culture?? along the Mendel??s lines of thought that was parallel to the first step of institutionalizing the new discipline of Genetics after 1905/06. Part of the study is also the analysis of contribution of his older brother Armin von Tschermak-Seysenegg (1870?C1952) who??much like in the case of ??rediscovery?? of 1900?C1901??was for his younger brother an important source of theoretical knowledge. In this particular case, it regarded Bateson??s ??Defence?? of Mendel from 1902.     

The real objective of Mendel's paper: A response to Monaghan and Corcos

Mendel's work in hybridization is ipso facto a study in inheritance. He is explicit in his interest to formulate universal generalizations, and at least in the case of the independent segregation of traits, he formulated his conclusions in the form of a law. Mendel did not discern, however, the inheritance of traits from that of the potential for traits. Choosing to study discrete non-overlapping traits, this did not hamper his efforts.     

What would have happened if Darwin had known Mendel (or Mendel's work)?

The question posed by the title is usually answered by saying that the "synthesis" between the theory of evolution by natural selection and classical genetics, which took place in 1930s-40s, would have taken place much earlier if Darwin had been aware of Mendel and his work. What is more, it nearly happened: it would have been enough if Darwin had cut the pages of the offprint of Mendel's work that was in his library and read them! Or, if Mendel had come across Darwin in London or paid him a visit at his house in the outskirts! (on occasion of Mendel's trip in 1862 to that city). The aim of the present paper is to provide elements for quite a different answer, based on further historical evidence, especially on Mendel's works, some of which mention Darwins's studies.     

L. H. Bailey's citations to Gregor Mendel

L. H. Bailey cited Mendel's 1865 and 1869 papers in the bibliography that accompanied his 1892 paper, Cross-Breeding and Hybridizing, and Mendel is mentioned once in the 1895 edition of Bailey's "Plant-Breeding." Bailey claimed to have copied his 1892 references to Mendel from Focke. It seems, however, that while he may have first encountered references to Mendel's work in Focke, he actually copied them from the Royal Society "Catalogue of Scientific Papers." Bailey also saw a reference to Mendel's 1865 paper in Jackson's "Guide to the Literature of Botany." Bailey's 1895 mention of Mendel occurs in a passage he translated from Focke's "Die Pflanzen-Mischlinge."     

William Bateson, human genetics and medicine

The importance of human genetics in the work of William Bateson (1861–1926) and in his promotion of Mendelism in the decade following the 1900 rediscovery of Mendel’s work is described. Bateson had close contacts with clinicians interested in inherited disorders, notably Archibald Garrod, to whom he suggested the recessive inheritance of alkaptonuria, and the ophthalmologist Edward Nettleship, and he lectured extensively to medical groups. Bateson’s views on human inheritance were far sighted and cautious. Not only should he be regarded as one of the founders of human genetics, but human genetics itself should be seen as a key element of the foundations of mendelian inheritance, not simply a later development from knowledge gained by study of other species.     

150 Jahre Mendel

The monk and his legacy: 150 years of Mendel The paper demonstrates how the experiments of Gregor Johann Mendel (1822–1884) with plant hybrids in the late 1860s revolutionized modern biology. It also shows how the commemoration of his anniversaries during the 20th century reflected the change of scientific epochs determined by the growth of genetics and related fields.     

The Case of Paul Kammerer: Evolution and Experimentation in the Early 20th Century

To some, a misguided Lamarckian and a fraud, to others a martyr in the fight against Darwinism, the Viennese zoologist Paul Kammerer (1880–1926) remains one of the most controversial scientists of the early 20th century. Here his work is reconsidered in light of turn-of-the-century problems in evolutionary theory and experimental methodology, as seen from Kammerer’s perspective in Vienna. Kammerer emerges not as an opponent of Darwinism, but as one would-be modernizer of the 19th-century theory, which had included a role for the inheritance of acquired characteristics. Kammerer attempted a synthesis of Darwinism with genetics and the chromosome theory, while retaining the modifying effects of the environment as the main source of favorable variation, and he developed his program of experimentation to support it. Kammerer never had a regular university position, but worked at a private experimental laboratory, with sidelines as a teacher and a popular writer and lecturer. On the lecture circuit he held forth on the significance of his science for understanding and furthering cultural evolution and he satisfied his passion for the arts and performance. In his dual career as researcher and popularizer, he did not always follow academic convention. In the contentious and rapidly changing fields of heredity and evolution, some of his stances and practices, as well as his outsider status and part-Jewish background, aroused suspicion and set the stage for the scandal that ended his career and prompted his suicide.     

On the origins of the Mendelian laws

The two laws usually attributed to Mendel were not considered as laws by him. The first law, the law of independent segregation occurs in Mendel's paper as an assumption or hypothesis. Hugo de Vries refers to this as a law discovered by Mendel. This appears to be the first use of an expression equivalent to Mendel's law. In his paper de Vries did not associate the observable characters with structures having a causitive role. That was done by Correns, who transformed the law of segregation of characters into a law of the segregation of anlagen. The second law, the law of independent assortment, is present in embryonic form in Mendel's paper. Here the independent assortment of characters appears as a secondary conclusion to a series of experiments involving several pairs of traits. Mendel repeats the primary conclusion later in the paper but not the secondary one. This leads us to believe that he considered the secondary conclusion as of lesser importance. We note in this context that the 9:3:3:1 ratio commonly associated with the idea of independent assortment, and attributed to Mendel, also does not occur in his paper. A careful reading of the papers of his discoverers shows it was Correns who first drew attention to this ratio. However, he did not formulate the second Mendelian law even though it was clearly implied. Neither was it stated by de Vries. Indeed, the first clear separation of the two laws and the naming of the second law was by T. H. Morgan some 13 years later.     

Abbey ambitions to celebrate home of genetics

A century and a half after the ground-breaking work by Gregor Mendel in establishing the foundation of genetics, efforts are under way to develop a fitting commemoration of his work at his abbey home in Brno. Nigel Williams reports.