Gregor Mendel

Gregor Johann Mendel (20 July 1822 – 6 January 1884) was an Austrian biologist, meteorologist, mathematician, and an Augustinian friar who served as abbot of St. Thomas' Abbey in Brno, in the Margraviate of Moravia. Born into a German-speaking family in the Silesian part of the Austrian Empire (now the Czech Republic), he is remembered after his death as the founder of modern genetics. Although farmers had understood for centuries that crossbreeding could promote certain desirable traits, Mendel’s work with pea plants from 1856 to 1863 laid down the fundamental rules of heredity, now called the laws of Mendelian inheritance.

Mendel studied seven traits in pea plants: plant height, pod shape and color, seed shape and color, and flower position and color. For seed color, he demonstrated that crossing a true-breeding yellow pea with a true-breeding green pea produced offspring that always had yellow seeds. In the next generation, however, green peas reappeared in a ratio of one green to three yellow. To explain this, Mendel introduced the terms “recessive” and “dominant.” In that case, the green trait—which seemed to disappear in the first generation—was recessive, and yellow was dominant. He published his findings in 1866, showing that invisible “factors” (now called genes) predictably determine an organism’s traits. The actual genes were identified only after a long process that concluded in 2025, when the last three of Mendel’s seven genes were located in the pea genome.

The importance of Mendel’s work went unrecognized for over three decades until the turn of the 20th century, when Erich von Tschermak, Hugo de Vries, and Carl Correns independently confirmed several of his experimental results in 1900, launching the modern era of genetics.

Mendel was born in Heinzendorf bei Odrau, Silesia, Austrian Empire (now Hynčice, Czech Republic), to Anton and Rosine (Schwirtlich) Mendel. He had an older sister, Veronika, and a younger sister, Theresia. The family lived and worked on a farm that had been owned by the Mendels for at least 130 years (the house where he was born is now a museum). As a child, Mendel worked as a gardener and studied beekeeping. He attended gymnasium in Troppau but took four months off due to illness. From 1840 to 1843, he studied practical and theoretical philosophy and physics at the Philosophical Institute of the University of Olomouc, taking another year off because of illness. He struggled financially to pay for his studies, and Theresia gave him her dowry. Later, he helped support her three sons, two of whom became doctors.

He became a monk partly because it allowed him to get an education without paying for it. As the son of a struggling farmer, the monastic life, in his words, spared him the “perpetual anxiety about a means of livelihood.” Born Johann Mendel, he took the name “Gregor” when he joined the Order of Saint Augustine.

When Mendel entered the Faculty of Philosophy, the Department of Natural History and Agriculture was led by Johann Karl Nestler, who researched hereditary traits in plants and animals, especially sheep. On the recommendation of his physics teacher Friedrich Franz, Mendel joined the Augustinian St. Thomas’s Abbey in Brno and began training as a Catholic priest. He worked as a substitute high school teacher. In 1850, he failed the oral part of his exams to become a certified teacher. In 1851, Abbot Cyril František Napp sponsored him to study at the University of Vienna, where his physics professor was Christian Doppler. Mendel returned to the abbey in 1853 as a teacher, mainly of physics. In 1854, he met Aleksander Zawadzki, who encouraged his research in Brno. In 1856, he again failed the oral part of the certification exam. In the summer of 1862, he joined an organized tour to Paris and London, visiting the International Exhibition and major scientific sites, a trip that may have influenced the final stage of his hybridization research. In 1867, he succeeded Napp as abbot.

After becoming abbot in 1868, his scientific work largely stopped due to administrative burdens, especially a dispute with the civil government over special taxes on religious institutions. Mendel died on 6 January 1884 at age 61 in Brno from chronic nephritis. Czech composer Leoš Janáček played the organ at his funeral. After his death, the succeeding abbot burned all papers in Mendel’s collection to end the tax disputes. An exhumation of Mendel’s corpse in 2021 provided some physiognomic details, such as body height. Analysis of his genome showed he was predisposed to heart problems.

Mendel, known as the “father of modern genetics,” chose to study variation in plants in his monastery’s experimental garden. He was assisted in his experimental design by Aleksander Zawadzki, while his superior Abbot Napp wrote to discourage him, noting that the Bishop giggled when informed of the detailed genealogies of peas.