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Gregor Mendel
1822–1884; pea experiments published 1866· Scientist· Plants & fungi
Well establishedStrong fossil, genetic or geological evidence.
Moravian friar who discovered the basic rules of inheritance by crossing pea plants in his monastery garden.
See it on the Life map →What happened
Mendel, an Augustinian friar in Brno (now in the Czech Republic), grew and crossed some 28,000 pea plants between 1856 and 1863, tracking seven traits such as seed shape and flower color. Crossing purple-flowered with white-flowered plants gave all purple offspring, but the next generation came out about three purple to one white. He concluded each plant carries two copies of a 'factor' for each trait and passes one, at random, to each offspring. Published in 1866, his work was ignored until 1900.
Why it matters
His rules became the foundation of genetics and solved the heredity problem that weakened Darwin's theory.
Discoveries and legacy
His 1866 paper, 'Experiments on Plant Hybridization', rediscovered by three botanists in 1900; his ratios have been reproduced countless times. His abbey in Brno now houses a Mendel museum.
Still debated
In 1936 statistician R.A. Fisher argued Mendel's results fit his ratios too well; whether the data were tidied, consciously or not, is still debated.
Connections (3)
▸Gregor Mendel found the inheritance rules produced by Sex & meiosisWell established
The connection
Mendel found that each plant passes one of its two 'factors' per trait to each offspring, at random, and that different traits sort independently. In 1902–1903 Walter Sutton and Theodor Boveri saw why: in meiosis, the cell division that makes eggs and sperm, paired chromosomes separate, one copy to each cell, and different pairs separate independently.
When and how
Mendel's pea crosses in Brno, 1856–1863; Sutton (Columbia University, grasshopper cells) and Boveri (Würzburg, sea urchins) linked them to chromosomes in 1902–1903.
The evidence
Thomas Hunt Morgan's fruit fly work from 1910 tied specific traits to specific chromosomes; today genes can be tracked through meiosis directly.
Debates and open questions
Genes close together on one chromosome do not sort independently; whether Mendel's seven traits avoided that by luck or careful choice is debated.
▸Gregor Mendel founded Genes & DNA: the science of heredityWell established
The connection
Mendel showed that traits pass on as discrete units in predictable ratios. Rediscovered in 1900 by Hugo de Vries, Carl Correns and Erich von Tschermak, his work became the core of a new science, which William Bateson named 'genetics' in 1905. Wilhelm Johannsen coined the word 'gene' in 1909.
When and how
Brno, Moravia, 1856–1866; rediscovery in the Netherlands, Germany and Austria in 1900.
The evidence
His 1866 paper and its rediscovery are well documented, and his basic ratios are reproduced in classrooms and labs every year.
Debates and open questions
Why his work went unnoticed for 34 years: an obscure journal, an unfamiliar mathematical style, and later hawkweed experiments that failed to fit his rules.
▸Gregor Mendel went unread by Charles DarwinWell established
The connection
Mendel read Darwin; his annotated German copy of the Origin survives. Darwin never read Mendel, though Mendel's paper solved the heredity problem Darwin struggled with. Darwin instead proposed 'pangenesis', an incorrect theory of particles shed by all body parts. He even recorded snapdragon crosses consistent with Mendel's three-to-one ratio, without seeing their meaning.
When and how
Mendel's paper, Brno, 1866; Darwin's pangenesis, 1868; Darwin died in 1882, 18 years before Mendel's rediscovery.
The evidence
Nothing in Darwin's letters or library shows he read the paper; a popular story that he owned an uncut copy has no evidence behind it.
Debates and open questions
Whether Darwin would have grasped its importance if he had read it; the few scientists who did read it in the 1860s did not.