The Father of Heredity

By Gabriel Blanchard

How did an obscure priest from the hinterlands of an extinct empire become one of the most eminent names in science?

No one would have predicted that Gregor Mendel, a sickly student who repeatedly failed exams, would become one of the most famous scientific minds of his century—especially not in light of the stiff competition put up by the nineteenth century, the time of such luminaries as Charles Darwin, Francis Galton, Michael Faraday, Marie Curie, and Nikola Tesla. Nevertheless, this Czech farmer’s boy was destined for greatness.

The area that is now the Czech Republic was at that time part of the Austro-Hungarian Empire, which dominated southeastern Europe and was overwhelmingly Catholic. Mendel became a monk and priest of the Augustinian Order (the same order that Martin Luther was at first a member of) in 1843, and took an interest in several branches of science. He helped found the Austrian Meteorological Society in 1865, studied and taught physics, and took a great interest in bees and beekeeping, which he had been fond of since childhood. (The records of his experiments with bees were for the most part not preserved, except for the tidbit that he used Cypriot and Carniolan breeds of bee, which irritated Mendel’s fellow monks with their aggressive behavior, so that he was asked to get rid of them!) But his most celebrated work was on genetics, in pursuit of which he experimented with mice, hawkweed, and, most importantly for posterity, peas.

The peas most of us eat today are green, but the plant comes in two varieties, green and yellow. Now, the fact that it is possible to breed both plants and animals to gain desired traits was perfectly familiar to any farmer and had been for many generations, of course; however, those endeavors were mainly practical, acquiring only as much knowledge as necessary to achieve results. Mendel was curious about the underlying factors, and began to experiment with green and yellow peas accordingly.

One always retains the traces of one's origin.

Ernest Renan

The dominant idea of heredity at the time was known as “blending inheritance,” the theory that the traits of offspring would be a blend of the traits of the parents. Through testing more than five thousand pea plants, however, Mendel reached a different conclusion. The first step was to find true-breeding plants, i.e. plants that (when bred with one another) always produced offspring with the same characteristics as themselves—in this case, color. In hybridizing true-breeding yellow peas with true-breeding green ones, a first generation of only yellow peas would result—but in the second generation, one in four of the plants derived from this hybridized stock would be true-breeding green peas, with the rest yellow. Further research would should that of the three yellow pea plants, one would be true-breeding and the other two capable of producing either yellow or green offspring. Mendel was thus able to identify the yellow trait as dominant and the green as recessive, meaning that a plant with one copy of the yellow gene would appear yellow regardless of whether the other copy it had was yellow or green, and only a plant with two copies of the green gene would appear green. (The terminology of genes and alleles was not coined by Mendel himself, but by William Bateson, a English scientist of the following century who helped to rediscover and popularize his work.)

Mendel investigated several traits of his pea plants in the same fashion—flower color (white or purple), flower position (mid-stem or end-stem), height (short or tall), pod form (full or constricted). His work was so fruitful and satisfied the needs of later biologists so exactly that in the 1930s, it gave rise to what was called the “Mendelian paradox”: namely, his data seemed so perfect that anybody would suspect forgery, but his character seemed so blameless that even unintentional error on his part seemed incredible! However, frequent repetitions of his experiments for well over a century have consistently returned results identical with Mendel’s own, so that both deliberate dishonesty and mere confirmation bias can be ruled out as influences on his work. Every once in a great while, people are astonishingly lucky, and apparently, Mendel got to be one of them.

In 1867, Mendel was chosen as abbot of his monastery and his researches largely came to an end, crowded out by administrative duties. His work was little known to the outside world for over thirty years; but, as Darwin’s theory of natural selection gathered steam, and understanding the exact mechanisms of heredity became more and more important accordingly, his work gained fresh attention. By the middle of the twentieth century, Mendel was recognized as the key to Darwinian, and thus to all modern, biology.


Gabriel Blanchard is CLT’s editor at large.

If you enjoyed this piece, you might like some of our other forays into science here at the Journal, like these profiles of Hippocrates, Francis Bacon, and Albert Einstein, or this student essay on the black hole information paradox.

Published on 11th April, 2022. Page image of Still Life with Peas by Mateusz Tokarsky, ca. 1795.

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