Peter van Dijk

Dr. Peter J. van Dijk PhD is a plant geneticist and Distinguished Scientist at Keygene in the Netherlands.  With T.H. Noel Ellis of the John Innes Centre in the UK, he has investigated numerous aspects of Mendel’s discoveries and history, including Mendel’s hybridisation research on Hieracium and other plant species, his travels abroad to London, Paris, Rome and other destinations, his perceptions of Darwin’s theory and writings, and his 1865 lectures compared to the article published in 1866.

 Mendel was a contemporary of Darwin and, as you have documented, travelled within a short distance of Down House when Darwin was there.  Could you briefly describe what the historical record tells us about the relationship (or lack thereof) between Mendel and Darwin?

In August 1862 Gregor Mendel took part in a group tour from Vienna by train, which, after a stay of a few days in Paris, spent a week in London to visit the great exhibition in Kensington.  It has been speculated that Mendel during those days in London might have met Charles Darwin.  Mendel’s theory of non-blending inheritance could have saved Darwin’s theory of evolution by natural selection from Fleeming Jenkin’s criticism that the fitter new variants would be swamped by crossing with a mass of less fit variants.  Loren Eiseley, therefore, called Mendel “the priest who held the key to evolution”.

One of the organised trips in London was to the Crystal Palace of the world exhibition of 11 years before, which had been moved to Sydenham Park, just eight miles as the crow flies from Downe, where Darwin lived.  From the letters, Darwin sent during that period it is clear that Darwin was at home in Downe.  Mendel would have been aware of Darwin’s theories, although he did not yet have a copy of the German translation of the Origin, since that appeared a year later, in 1863.

There are, however, several reasons why a meeting between the two greatest biologists of the 19th century could not have taken place.  Mendel was a humble person, and it is unlikely that he would have approached famous naturalist Charles Darwin.  There was also the language barrier.  Darwin could read German with great difficulty with the help of a dictionary.  However, he could not speak German.  Neither could Mendel speak English or French.  Moreover, Mendel’s theory was not yet completed since his final pea crossing experiments, in which he would test his ideas about the composition of the reproductive cells, would run for two more years.

Even though the meeting did not take place, one may wonder what would have happened if Darwin and Mendel had met.  It has been suggested that Darwin would have been scared off by Mendel’s formulas, but Mendel’s algebra is rather simple and not difficult to comprehend.  What often is forgotten is that Darwin was highly interested in variation in peas.  In 1855, Darwin grew 41 different pea varieties at Downe, even more than Mendel, who grew 34 varieties in the same year at the monastery in Brünn (now Brno).  Throughout his life, Darwin remained in contact with the famous British pea breeder Thomas Laxton whom he repeatedly cited in several editions of his Variation of Animals and Plants Under Domestication.  In November 1862, a few months after Mendel’s visit to London, Darwin sent a letter to The Gardeners’ Chronicle with questions about the origin of certain pea varieties.  Peas were a shared interest and if they had met and had there not been a language barrier, Darwin could have been convinced by Mendel’s elegant numerical results.  Mendel knew that his findings were not only restricted to discrete variation but could also be extrapolated to continuous variation depending on many factors with minor effects.  Therefore, he may not have been as disbelieved by Darwin as Charles Naudin, the French hybridiser with whom Darwin corresponded regularly.

If the Mendel-Darwin meeting had taken place in 1862, it is also likely that Mendel would have later sent Darwin one of his 40 reprints of his 1866 paper “Experiments in Plant hybridisation”.  It is a persistent myth that Darwin possessed one of these reprints.  No such reprint has been found in Darwin’s reprint collection.  Biology would have to wait more than 65 years until the final merger of the ideas of Darwin and Mendel would take place in theoretical population genetics by Fisher, Wright, and Haldane.