Gregor Mendel

Gregor Mendel was an Augustinian friar and teacher in Brno, in the Austrian province of Moravia, whose experiments with pea plants revealed the basic rules of heredity. His results, presented in 1865 and published the following year, were almost entirely ignored in his lifetime. Rediscovered in 1900, they became the starting point of modern genetics, and he is now often called its father.

Johann Mendel was born on 20 July 1822 at Heinzendorf in Austrian Silesia, now Hynčice in the Czech Republic. His German-speaking family had farmed the same land for at least 130 years, and as a boy he tended the garden and learned beekeeping. From 1840 to 1843 he studied philosophy and physics at Olomouc, interrupted by illness and constant shortage of money; his younger sister Theresia gave him her dowry to help pay for his studies.

Becoming a monk offered a way out. In his own later account, it spared him perpetual anxiety about earning a living. On the recommendation of his physics teacher, he joined the Augustinian community of St Thomas's Abbey in Brno, then known by its German name Brünn, where he took the religious name Gregor.

The abbot, Cyril Napp, himself oversaw sheep breeding on the abbey's estates. Mendel worked as a substitute schoolteacher but failed the oral part of the state teaching examination in 1850. In 1851 the abbot sent him to the University of Vienna, where his physics professor was Christian Doppler. He returned to Brno in 1853 to teach, mainly physics, though he failed the teaching examination again in 1856.

Between 1856 and 1863 Mendel grew and tested some 28,000 plants, most of them garden peas, in the abbey's experimental garden. He followed seven traits that appeared in two clear forms, among them seed shape, seed colour, flower colour and plant height. When he crossed true-breeding yellow and green peas, every plant of the next generation had yellow seeds; but in the generation after that, green seeds returned in about one plant in four.

To explain this he described some traits as dominant and others as recessive, and proposed that each plant carries paired hereditary factors, one from each parent, which separate when seeds are formed and are passed on independently of one another. These ideas became known as the laws of segregation and independent assortment. His factors are what are now called genes.

Mendel presented his findings, Experiments on Plant Hybridization, to the Natural History Society of Brno on 8 February and 8 March 1865. About forty people heard him, but few seem to have grasped the significance. Published in 1866, the paper was read mainly as a study of hybrids and drew only around three citations in the following 35 years. Charles Darwin, whose theory of evolution lacked a sound account of inheritance, never knew of it.

Mendel's other interests included bees, hawkweeds, astronomy and especially meteorology, the subject of most of his publications. After he became abbot in the late 1860s, administrative work and a long dispute with the government over taxes on monasteries largely ended his research. He died of chronic kidney disease in Brno on 6 January 1884, aged 61. His successor burned his papers.

In 1900 Hugo de Vries and Carl Correns, working independently, reached similar results and found Mendel's paper, and both acknowledged his priority. The English biologist William Bateson championed the theory and coined the word genetics. Combined with Darwin's natural selection in the 1930s and 1940s, Mendelian heredity formed the core of the modern evolutionary synthesis.

His data have been debated. In 1936 the statistician Ronald Fisher argued that the reported ratios were suspiciously close to expectation. Later scholars, including Daniel Hartl and Daniel Fairbanks, have rejected the charge that he falsified his results. In 2025 researchers identified the last of the seven pea genes behind the traits he studied.

Mendel lived in the Austrian lands of the Habsburg monarchy. Our 1815 map shows Moravia and Silesia within the Austrian Empire of his youth, and the 1878 map shows them in Austria-Hungary during his last years as abbot.