Jul 202013



Today is the birthday (1822) of Gregor Johann Mendel, a German speaking Silesian scientist and Augustinian friar who gained posthumous fame as the founder of the new science of genetics.  Mendel was born into an ethnic German family in Heinzendorf bei Odrau in Silesia in what was the Austro-Hungarian Empire (now Hyn?ice, Czech Republic). He was the son of Anton and Rosine (Schwirtlich) Mendel, and had one older sister (Veronica) and one younger (Theresia). They lived and worked on a farm which had been owned by the Mendel family for at least 130 years.

Mendel worked on the family farm as a gardener and studied beekeeping until the age of 11. At that point a local schoolmaster who was impressed with his intellect recommended that he go to Troppau to a secondary school.  This was an unusual step because in that era in the Western world the vast majority of boys left school at 11 and took up work on farms, began apprenticeships, or the like.  His family had to take on the burden of financing his education whilst not having him around to work.  But they acquiesced and he graduated with honors in 1840.

Following his graduation, Mendel enrolled in a two-year program at the Philosophical Institute of the University of Olmütz. There, he again distinguished himself academically, particularly in the subjects of physics and mathematics, and tutored in his spare time to make ends meet. Despite suffering from deep bouts of depression that, more than once, caused him to temporarily abandon his studies, Mendel graduated from the program in 1843.

That same year, against the wishes of his father, who expected him to take over the family farm, Mendel began studying to be a monk. He joined the Augustinian order at the St. Thomas Monastery in Brno, and was given the name Gregor (his birth name was Johann).  At that time, the monastery was a cultural center for the region, and Mendel was immediately exposed to the research and teaching of its members, and also gained access to the monastery’s extensive library and experimental facilities.

In 1849, when his work in the community in Brno exhausted him to the point of illness, Mendel was sent to fill a temporary teaching position in Znaim. However, he failed a teaching-certification exam the following year, and in 1851, he was sent to the University of Vienna, at the monastery’s expense, to continue his studies in the sciences. While there, Mendel studied mathematics and physics under Christian Doppler, after whom the Doppler effect of wave frequency is named; he studied botany under Franz Unger, who had begun using a microscope in his studies, and who was a proponent of a pre-Darwinian version of evolutionary theory.

In 1853, upon completing his studies at the University of Vienna, Mendel returned to the monastery in Brno and was given a teaching position at a secondary school, where he would stay for more than a decade. It was during this time that he began the experiments for which he is best known. Around 1854, Mendel began to research the transmission of hereditary traits in plant hybrids. At the time of Mendel’s studies, it was generally believed that the hereditary traits of the offspring of any species were merely the diluted blending of whatever traits were present in the “parents.” It was also commonly accepted that, over generations, a hybrid would revert to its original form. Mendel’s work on the propagation of peas completely overturned these assumptions.

Mendel chose to study what happened over several generations to 7 traits of peas as they were mixed and matched:

1.Form of ripe seed     Smooth vs Wrinkled
2.Color of seed albumen Yellow vs Green
3.Color of seed coat     Grey vs White
4.Form of ripe pods     Inflated vs Constricted
5.Color of unripe pods     Green vs Yellow
6.Position of flowers     Axial vs Terminal
7.Length of stem     Tall vs Dwarf


The first thing he discovered was that there was no blending. If, for example, he paired a plant with green pods with one with yellow pods, the pods of the next generation were either green or yellow, and not some greenish-yellow in between.  He also discovered that a characteristic might disappear for a generation and then reappear in the next. Furthermore, he discovered that these seven traits were completely independent of one another, and could be passed on in any combination.

Over 8 years he developed the notion of dominant versus recessive traits.  He theorized that every plant has two genes per trait and passes one on to the next generation, the partner plant providing the other.  In this way every plant can have one of four gene combinations: dominant::dominant, dominant::recessive, recessive::dominant, recessive::recessive. If the dominant gene is present AT ALL it masks the recessive.  So, for example, if smooth seeds is a dominant trait, it will appear in the first three combinations, but not the last.  In theory, therefore, over time any trait should be represented in each generation by more or less ¾ of the plants (although experimental conditions won’t make this exact). This is what Mendel’s experimental data show.

Mendel's notes on peas

Mendel’s notes on peas

During his 8 years of study Mendel made 287 crosses between 70 different purebred plants, producing approximately 28,000 pea plants.  He formulated two principles which are now called Mendel’s Laws and are the cornerstone of genetics.  They are: 1. The Law of Segregation (a parent has two genes for each trait and passes ONE of them on to the offspring). 2. The Law of Independent Assortment (separate genes for separate traits are passed independently of one another from parents to offspring).

Mendel published his findings in 1866 to vast indifference in the scientific community because no one could understand what he was saying, nor recognize the profound value of his discoveries because they did not fit current theory. Mendel died before the scientific community caught up with him.  Blending inheritance continued to be the dominant theory until around 1900. It is a sad fact, repeated through history, that you can be right but your ideas rejected because they fail to support prevailing views.  By 1900, research aimed at finding a successful theory of discontinuous inheritance rather than blending inheritance led to independent duplication of Mendel’s work by Hugo de Vries and Carl Correns, and the rediscovery of Mendel’s writings and laws. Both acknowledged Mendel’s priority, and it is thought probable that de Vries did not understand the results he had found until after reading Mendel.  What always astounds me when I think about Mendel and his peas is that even with 28,000 plants and data gathered over 8 years, I and millions of others, would NEVER have the flash of insight to put it all together to come up with the conclusions Mendel did. That is the mark of pure genius.

For a recipe I have no choice.  It has to be Silesian pea soup.  Fortunately there is such a thing.  It’s close kin to classic split pea soup, but with important differences.  First, it is made from whole dried peas and not splits.  These produce a markedly different flavor. Second, it uses fresh pig bits rather than smoked. Apart from the trotters and skin these may be hard to find.  I can get snouts and ears in Argentina on occasion. Use what you can find.  It also uses parsley root which can be a bit hard to find, but makes a difference.


Silesian Pea Soup


1 lb (500 g) whole dried peas, soaked overnight
1 stalk celery diced
1 carrot peeled and diced
1 leek sliced thin
1 onion peeled and chopped coarsely
1 parsley root peeled and diced
1 large potato peeled and diced
1 small bunch fresh parsley chopped fine
1 small bunch fresh lovage chopped fine
1 tsp allspice
salt and pepper
1 lb (500g) any combination of pig’s trotters, ears, snout, and skin


Fry the pig parts in a heavy skillet until they are golden brown.

Put the pig parts, peas, and allspice into a large soup pot and cover with water.  Add salt and pepper to taste.

After about an hour remove the pig parts, strip the meat from the trotters, and chop up whatever else is edible.  With a potato masher, mash up some (but not all) of the peas.

Return the meat to the pot and add the vegetables and herbs.

Simmer until the vegetables are cooked.

Serves 6