Formulating the foundational principles of heredity—by experimenting in a monastery garden
Gregor Mendel
(1822–1884)
The pious do not become monks to disrupt the world, and neither do gardeners. Yet Gregor Mendel was both a monk and a gardener—albeit with scientific training—whose patient experiments with the humble pea plants in the garden of his monastery allowed him to outline the basis of heredity. With Mendel, the study of genetics began.
He was born Johann Mendel on July 22, 1822, to a farming couple, Anton and Rosine Mendel, in what was called at the time Heinzendorf, Austria. He would surely have become a farmer had not the local schoolmaster appreciated the eleven-year-old boy’s zeal for learning and depth of understanding. He recommended that the youngster progress to a secondary school in Troppau. Despite the high financial cost of the move, Mendel’s parents journeyed to Troppau and enrolled Johann. Shy and timid, Johann had a great deal of trouble adjusting to life in the larger town—and yet he was anxious to justify his parents’ sacrifice. He worked hard, graduating with honors in 1840.
From the school at Troppau, young Mendel enrolled in a two-year course of study at the Philosophical Institute of the University of Olmütz. He excelled again, especially in mathematics and physics, and found work as a tutor, which defrayed both tuition and living costs. Yet the emotional toll on him was heavy. Seriously depressed, he was forced at one point to suspend his studies, but recovered sufficiently to continue, and in 1843 he completed the program.
But Mendel then took a turn that pleased neither his professors, who expected him to continue on to a scientific career, nor his father, who expected him to take over the family farm. Instead, he embarked upon the rigorous course of study and devotion necessary to prepare for life as a monk. In quiet and solitude, perhaps he hoped to find the peace that evaded him in other pursuits. He was embraced by the Augustinians at the St. Thomas Monastery in Brno and took, upon his ordination, the name Gregor.
While he had expected to live a retired and contemplative life, Gregor Mendel found himself in a monastery that was the region’s center of culture and learning. Many of his fellow monks were engaged in research and teaching. The monastery had a large modern library, which was not restricted to works of religion but also contained the latest scientific publications. There were also well-equipped laboratories.
Mendel threw himself into study and research to the point of debilitation and serious illness. Concerned for him, his superiors sent him off in 1849 to teach in the Moravian town of Znaim (modern Znojmo, Czech Republic). When he failed to pass the examination for his teaching certificate in 1850, the monastery paid for his enrollment at the University of Vienna, where he studied mathematics and physics under the eminent Christian Doppler (for whom the Doppler effect is named) and botany under Franz Unger, a forward-looking scientist who was an accomplished microscopist and a prescient exponent of biological evolution—some eight or nine years before Charles Darwin published his On the Origin of Species (1859).
Completing his university studies in 1853, Mendel returned to the monastery in Brno, where he was assigned to teach at a secondary school associated with the order. His career here spanned a decade, during which he began conducting, in 1854, the experiments that constituted his research in the transmission of hereditary traits in plant hybrids.
The prevailing theory during this period—a theory so pervasive as to be accepted as self-evident fact—was that the hereditary traits of the offspring of any species were nothing less than the diluted blending of traits present in the parents, as if genetic material were some homogenous brew capable of dilution down through the generations. It was further assumed that, given a sufficient number of generations, any hybrid would revert to its original form, the variations having been sufficiently diluted. Thus, a hybrid could never create new permanent forms. Both of these commonly accepted assumptions were dubiously confirmed by a handful of desultory observations. Mendel noted, however, that no scientist had ever devoted sufficient time to confirm these observations over many generations. As a monk, time was one commodity he possessed in abundance. A godly, patient man, he was in no hurry. Between 1856 and 1863, Mendel conducted his quiet experiments on tens of thousands of individual plants, each of which he meticulously observed and notated.
His choice of experimental subject was very deliberate. He chose peas. They were rich in their highly distinctive varieties, and their offspring were quickly and readily produced. Mendel concentrated on cross-fertilizing plants with the most distinctly opposite characteristics. He crossed short with tall, wrinkled with smooth, those producing green seeds with those producing yellow. His purpose was to reduce the subjective factors of observation to a minimum. And, after years of observation, he was prepared to formulate two breakthrough conclusions.
First was the Law of Segregation, which demonstrated that some traits are dominant and others recessive. These traits are passed down randomly from parents to offspring. The concept of dominant and recessive traits disproved the universally accepted notion that inheritance is a matter of simply blending traits. Second was the Law of Independent Assortment, in which each trait was passed down independently of other traits. Beyond these two conclusions, Mendel, well trained in mathematics, theorized that heredity follows the basic laws of statistics. Boldly, he claimed that his experiments on pea plants applied to all organisms with identifiable traits. In other words, he had discovered basic and universal principles of heredity.
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Mendel presented his findings in two 1865 lectures before the Natural Science Society in Brno. The society also published his studies in its journal in 1866 under the misleadingly modest title “Experiments on Plant Hybrids.” This generic, noncommittal title, together with Mendel’s own constitutional disinclination to promote his own work, meant that its disruptive impact was hardly appreciated at the time. Those relatively few who read his study assumed that Mendel was merely reaffirming what had already been generally observed. This is understandable due to the simple reason that Mendel failed to underscore the differences and refused to tout the magnitude of his breakthrough. Worst of all, many readers of his study took the work as confirmation—not refutation—of the simple assumption that all hybrids revert eventually to their original form.
The fact is that even Mendel himself seems to have failed to appreciate the magnitude of what he had observed. He did not pursue his observations on variability to their full significance for evolution. Moreover, he retreated from his original claim that his findings applied to all species and all types of traits. Thus, Mendel’s work was not seen as essentially disruptive until years later, when it was rediscovered and interpreted in the context of Darwin.
If Gregor Mendel felt any disappointment, none was apparent. He seemed quite content to be elected, in 1868, abbot of the school in which he had taught for fourteen years. This position, however, required him to do a good deal of administrative work. For these reasons, his career as an experimental scientist was effectively at an end, which may have been just as well since his eyesight, so essential to observational work, had dimmed with the passing years.
Mendel died on January 6, 1884, a respected religious figure within his small circle, but little known as a scientist. Years would pass before his fundamental work was rediscovered and recognized for what it was. In 1900, three botanists, Hugo de Vries, Carl Correns, and Erich von Tschermak-Seysenegg, together duplicated Mendel’s experiments and results. They claimed their results as having been independently reached. They said that they published before they became aware of Mendel’s 1866 paper. Not everyone believed them. Accused by some of plagiarizing Mendel and taking credit for his work, the trio scrambled to give the monk credit for what he had done. Thus, in this backhanded way, Mendel was brought posthumously into the limelight.
Even so, his work met with resistance from some Darwinians, who discounted its relevance to the theory of evolution. Only by the second quarter of the twentieth century were the observations of this modest man recognized as absolutely essential to understanding the field of genetics. They were seen as what they had been: the first major insights into the process of hereditary transmission before the discovery of the visualization of the DNA double-helix model by Francis Crick and James Watson in 1953.