When we refer to the life sciences, terms such as DNA, gene, genetic engineering, and genome editing have now become part of both specialized and popular scientific language. Since the second half of the twentieth century, the frontiers of the life sciences have expanded exponentially thanks to new discoveries and the application of advanced technologies. At the origins of such admirable scientific progress we find a gentle, affable, reserved and industrious friar, Johann Gregor Mendel, abbot of the Augustinian Abbey of St. Thomas in Brünn (Brno), which is currently located in the Czech Republic. Mendel pioneered the studies that contributed to the birth of genetics and later molecular biology and genomics. When talking about heredity, transmission of traits and population genetics, one cannot but refer to Mendel. Life sciences owe a great debt to this figure for a number of reasons that we will briefly outline here.
Born on July 22, 1822, into a deeply Christian family of small farmers, he completed his early studies in his native country, moved to Olmütz (now Olomouc) and devoted himself to the study of philosophy. With very little money and a family that could not support him, on the advice of his physics teacher, Frederich Franz, he entered the Augustinian monastery of Brünn in 1843, where he was ordained a priest on August 6, 1847. From this point on, Mendel's life would be devoted to study and research. The Abbey, under the leadership of Abbot Cyril Napp, was a place of great cultural ferment in mid-nineteenth-century Brünn. A member of the leading local scientific societies, a lover of science but also of oriental languages, Abbot Napp encourages the monks to study, protects them and even shields them from the accusations, later deemed unfounded, made by the bishop of Brünn, of devoting too much energy to worldly studies and neglecting religious and spiritual obligations. Mendel thus benefits from the support of an abbot who conceived no dichotomy between faith and reason, between "contemplating God in se and contemplating God in creatio". Mendel's scientific interests (especially in mathematics, but also in meteorology, in the study of bees, and in the mechanisms of hybridization) became apparent early on, and Abbot Napp enabled him to complete his scientific training at the University of Vienna between 1851 and 1855. In Vienna, Mendel breathes an atmosphere of great openness and intellectual confrontation. He enrolls in physics, mathematics, chemistry, zoology and botany courses. In particular, he got to know and befriend botanical physiologist Franz Unger and botanist Karl Wilhelm von Nägeli. Unger is a fervent evolutionist, convinced, even before the publication of Charles Darwin's famous study On the Origin of Species (1859), that all living things have a common origin and that new species can emerge from earlier species. Some of his publications aroused the ire of influential Catholic priest Sebastien Brunner, who accused Unger of denying creation and the very existence of a Creator.
Mendel entertained correspondence with Wilhelm von Nägeli, a professor of botany, for several years. Nägeli is perhaps one of the few, if not the only, famous scientist who shows the slightest interest in Mendel's work, although he treats the monk's studies with perplexity and their author as a mere amateur.
Back in Brünn in 1854, enriched by his studies in mathematics, statistics and botany, Mendel began hybridization experiments in his monastery garden, selecting 22 varieties of peas and focusing on 7 pairs of opposite properties. From 1854 to 1865, he analyzed thousands of Pisum sativum plants and arrived at the formulation of the famous three laws of genetics (law of dominance and uniformity, law of segregation, and law of independent assortment), which he presented in two lectures at the Brünn Natural Science Society (of which Mendel was a founding member) on February 8 and March 8, 1865, respectively. Mendel's manuscript will see publication the following year among the Proceedings of the Society itself. However, it will not receive much attention from the scientific community until, thirty-five years later, it will be rediscovered simultaneously by three scientists who came to the same conclusions as this unknown Augustinian abbot. Only at this time will its revolutionary significance be fully appreciated. Indeed, Mendel's great merit is that he applied the mathematical and statistical method to biology, a method not appreciated at all by another great father of modern biology, Charles Darwin. So much has been said about the failed relationship between Mendel and Darwin. The two authors never met personally. According to some scholars, Darwin had in his library Wilhelm Olbers Focke's text The plants hybrids (1881), which summarized Mendel's experiments, but the pages are found to be uncut and thus the book unread. Mendel, on the other hand, was familiar with Darwin's work and his theories, indeed he owned and had annotated the German translations of On the Origin of Species and The Variation of Animals and Plants under Domestication. Darwinian theory, although it was not the main motivation for Mendel to begin his experiments in 1854 (five years before the English publication of On the Origin of Species), nevertheless influenced Mendel's interpretation of the data he collected. As just mentioned, Mendel owned both volumes of the German translation of The Variation of Animals and Plants under Domestication edited in 1868 by Julius Victor Carus. In the first volume there are 5 annotations by Mendel, in the second as many as 57, concentrated mainly in chapters 15 and 27 where Darwin talks about the "provisional hypothesis of pangenesis". According to Darwin's theory, parental characters were inherited by offspring through "gemmules," microscopic particles found in every part of the organism, which would be passed on to offspring through sex cells. However, the male possessed a relevant role in fertilization and thus in the possible transmission of "gemmules." This is a quite different hypothesis from Mendel's laws, which state that genetic information is inherited in the form of discrete, separate, independent elements – the very elements that in 1909 Wilhelm Johannsen would call "genes." As opposed to the idea of a mixing of parental traits proposed by Darwin, Mendel thus hypothesizes the possibility of independent inheritance of maternal and paternal traits. In the notes in the margin of the copy of Darwin's text, Mendel makes a critique of the Darwinian theory of pangenesis, probably never made publicly explicit, however.
Mendel had a keen sense of humor (he was a subscriber to the humor magazine Fliegende Blätter, whose jokes he underlined and then told to the other monks at convivial times) and was fond of chess and Tischkegelspiel (table bowling). Growing up from childhood in a deeply religious atmosphere (a tile on the roof of his birth house with the image of the Trinity represented by three intertwined circles with the inscription "Thy will be done" has been discovered), he was both shy and reserved (in photographs he often appears holding his favorite flower, the Fuchsia, in the act of contemplating it, looking away from the cameras). As a science teacher he was loved and respected by his students, and he devoted himself to his scientific research with constancy, spirit of sacrifice and perseverance. He died on January 6, 1884, and just after his death, on the hill next to the abbey, his brethren burned his private papers, as was the custom. Because of this, very few letters or other direct sources about his life have survived, such as his notes, his observations on hybridization experiments, and his personal papers.
He died without having his observations and hypotheses appreciated. He was, however, well aware of the relevance of his findings, to the point that he seems to have said, shortly before his death, "Meine Zeit wird kommen" (My time will come).
This happened at the turn of the 20th century, when, in the year 1900, three scientists (Hugo de Vries of the Netherlands, Carl Correns of Germany, and Erich von Tschermak of Austria) rediscovered his writings and arrived, through different paths, at the his same conclusions. Thus begins the long journey of modern biology. The revolutionary importance of Mendelian ideas for understanding hereditary transmission is immediately recognized. English zoologist William Bateson, in a lecture at the Royal Horticultural Society on May 8, 1900, presents Mendel's research, publishing and translating Mendel's paper on the principles of heredity in 1901. Thanks to Bateson's great popularizing work, Mendel would soon receive due honors from the entire international scientific community. Bateson himself coined, in 1905, the term "genetics" to refer to a new scientific doctrine. Research and studies on heredity take on new vigor thanks to Mendel's theories, which for the first time apply mathematical and statistical methods to biology. This methodology would open up new and unexpected perspectives and research fields, which, throughout the twentieth century, would follow one another at a rapid pace. The term "chromosome" had been coined by the German anatomist Wilhelm Gottfried von Waldeyer-Hartz in 1889, but as early as 1903 the biologist Walter Sutton published an article pointing to chromosomes as the carriers of the hereditary traits identified by Mendel. As mentioned above, in 1909 plant physiologist Wilhelm Johannsen proposed the term "gene" to refer to the factor transmitted from parent to offspring carrying information related to a single character. Later, biologist Thomas Hunt Morgan, aware of the importance of chromosomes in the mechanisms of hereditary transmission, began studies on a small fruit fly that would become famous among twentieth-century biologists and geneticists: Drosophila melanogaster. After a series of experiments Morgan comes to the demonstration that genes are contained within chromosomes. As a result of Morgan, Hermann Muller and Charlotte Auerbach's studies of genetic mutations, the evolutionary role of small mutations in producing the biodiversity upon which natural selection acts to promote the evolution of entire populations becomes clear. The great process of fusion between Mendelian genetics and evolutionary Darwinism that would lead to the birth of the "Modern Synthesis," an expression coined by Julian Huxley in 1942, was now beginning. The conference organized at Princeton in 1947 entitled "Genetics, Paleontology and Evolution" marks the completion of this long process of rapprochement between Mendel and Darwin. What an essential piece Mendel brought as a gift to Darwinian theory!
Subsequent research was bound to be revolutionary: from the discovery of DNA as the informational basis of life by scientists James Watson and Francis Crick, to the study of gene expression patterns by François Jacob and Jacques Monod, to the birth of modern molecular biology, the "Human Genome Project," genomics and proteomics, to the most recent frontiers of genome editing through CRISPR/Cas9 technology, which makes it possible in a rapid and inexpensive way to modify or replace individual genes even in germ cells.
This is the scientific-historical path that makes Life Sciences deeply indebted to an Augustinian abbot who lived in Brünn in the mid-nineteenth century and who, while not holding an official academic position, devoted himself to performing meticulous experiments in hybridizing plant species in his garden. A priest and at the same time a man of science who was able to harmonize perfectly in himself spiritual contemplation of, and scientific experimentation within, the creation.
Now to the texts offered in this special:
The first text is a translation of the editorial Gregor Mendel and genetics, between discovery and "invention," 200 years after his birth, written by Ivan Colagè and published on disf.org. The reader will delve into the Mendelian language, the formulation of the laws of genetics, and the implications and developments they bring about, not only for modern biology but also for the very life of the monk and later abbot Mendel.
The second text is a paper by Daniel J. Fairbanks, titled Mendel and Darwin: untangling a persistent enigma, in which he analyzes the relationship between these two great scientists, who lived and worked at the same time, but whose relationships continue to be not entirely clear.
The third proposed text is a fragment of an undated Easter Sermon, probably delivered by Mendel after his appointment as abbot around 1867. In this sermon, Mendel uses the suggestive image of the deity as a great gardener who offers human beings talents that, combined with divine grace, may blossom like so many seeds placed in the earth.
The fourth text Remembering Johann Gregor Mendel: a human, a Catholic priest, an Augustinian monk, and abbot, written by one of Mendel's great-grandsons, shows the great devotion of this scientist, the deep religious faith inherent even in his family of origin, his kind and friendly character, and his desire, expressed to friends and brethren to see his immense work finally recognized and appreciated.
The fifth text is an English translation of the lecture given by Mendel on February 8 and March 8, 1865 at the Natural Science Society in Brünn and published the following year in the Proceedings of the Society. The reader will appreciate the innovative ideas of the father of genetics.
Closing the special issue is a video on Gregor Mendel and the History of Genetics, that shows, in a familiar language, the experiment that Mendel did with pea plants, looking at pea colour, flower colour, and height, and how he discovered hereditary units, which could be recessive or dominant.
DISF Center, Pontifical University of the Holy Cross