Why didn't Mendel's experiments draw attention until the 20th century?

Question

In The Gene: An Intimate History, author concludes the Mendel's pea experiments publication by these words:

Mendel himself requested forty reprints, which he mailed, heavily annotated, to many scientists. It is likely that he sent one to Darwin, but there is no record of Darwin’s having actually read it.

What followed, as one geneticist wrote, was “one of the strangest silences in the history of biology.” The paper was cited only four times between 1866 and 1900—virtually disappearing from scientific literature. Between 1890 and 1900, even as questions and concerns about human heredity and its manipulation became central to policy makers in America and Europe, Mendel’s name and his work were lost to the world. The study that founded modern biology was buried in the pages of an obscure journal of an obscure scientific society, read mostly by plant breeders in a declining Central European town.

I wonder what could be the reason for that. If we attribute only to Mendel being a low-key monk from Brno, then still just 4 citations don't do justice given the Genetics and Heredity was arguably dawning right then.

Does it have something to do with his radical ideas - but if that is the case, then Darwin's ideas were much more challenging to the Church in my opinion. I am interested to know the possible reason(s) behind this "one of the strangest silences in the history of Biology"

Answer 1

This is a supplement to J.G.'s useful answer: there is a good deal of illuminating source material in William Bateson's (1909) "Mendel's principles of heredity", available at (https://archive.org/details/mendelsprinciple00bate), which was cited by the Gasking 1959 paper. Bateson gave translations of both of Mendel's major papers.

Some points from Gasking's (1959) paper, cited by J.G.: her explanation for Mendel's neglect argued several points. The prevailing perspective on breeding experiments was that of a farmer/horticulturalist, different from a scientific perspective, and linked with reluctance to seek general conclusions from observational facts gained from breeding experiments. Gasking found that some elements of Mendel's observations had been seen [long] before, e.g. by "workers, such as Goss and Seton, [who] were also breeding peas. Goss (John Goss, "On Variations in Colour of Peas Occasioned by Cross-Impregnation," Trans. Hort. Soc., V (1824), 235) actually noted that, if a white-seeded variety were crossed with a blue- [= green-] seeded type, the hybrid produced only white seeds. He also remarked, first, that amongst the next generation blue seeds appeared once more, and that, if plants grown from these seeds were planted and allowed to self-fertilize, all the subsequent generations were blue-seeded: the white seeds meanwhile continued to produce both white and blue-seeded plants. It was perfectly consistent with the aims of these workers that Goss, having made this discovery, was content to record it as a fact, and made no attempt to follow it up, in the hope of establishing a more general law."

Gasking also pointed out that the development of thought of the 19th-century had been hindered by "extreme vagueness: experimenters would report simply that a hybrid 'resembled' the maternal or paternal species more or less closely, or that it was intermediate -- they did not even trouble to say in what respects (flower-color, height, etc.) the resemblances appeared."

Thus there was vagueness in the 'species' concept itself, but "In tackling the theory of inheritance as a problem about unit-characters rather than unit-species, Mendel's work was thus completely novel." [and at some distance from contemporary ways of thinking].

Answer 2

Elizabeth B Gasking summarised the reasons in 1959, but you're not reading it without a Jstor account.

Sometimes a paper is overlooked because we think about its relevance from the wrong perspective. It seems even Mendel didn't realise what he'd uncovered. The laws of inheritance that now bear his name, insofar as he formulated them in something close to their modern form, were imagined - by him, not just his readers - to have a very limited scope, in terms of which species and traits they applied to. This is partly because, as was typical of biologists of the time, he usually thought about inheritance in terms of blending. He called the paper Experiments on Plant Hybridization, and the general perception was that it was a minor fact about how certain plants hybridise, not a general realisation that heredity is digital. (Before the theory of computers, that concept may have been a bit beyond us.)

Answer 3

I can answer this part of the question: "It is likely that he sent one to Darwin, but there is no record of Darwin’s having actually read it."

No, Darwin never received Mendel's paper. That author's speculation is wrong. None of his biographers have found evidence of this paper, or that he was aware of its publication. It was in a quite obscure journal.

I am intimately acquainted with Darwin research notes from before he formulated his theory until his death. He makes no mention of Mendel. Darwin would have been very interested in the research, since he conducted many breeding experiments with plants, and had a garden just for this at his home.

Darwin accumulated tens of thousands of research notes. I have transcribed, edited, or otherwise worked with thousands of these, and I've never seen a mention of Mendel. About 20,000 of these notes, plus manuscripts, are available on the Darwin Manuscripts Project site at the American Museum of Natural History.

Our editor-in-chief, Professor David Kohn, was a Darwin scholar for his entire career. He assures me Darwin had no knowledge of Mendel or his work.