That Man Mendel, by William Bennett

The case of Gregor Mendel is one of the unsatisfactory enigmas of biology. There’s not quite enough evidence to bring in a unanimous verdict either way.

In the absence of more and better information, some geneticists are content to leave the case as Great Eternal Mystery #76824: others cite it as an appalling lapse of taste on the part of the Almighty.

On the one hand there was the Augustinian monk, shy, stubbornly, make that righteously, resisting Austrian taxes on his little monastery in Br¨unn, tending his bees, tending his mice, tending his pea plants, wiping his honestly soiled hands on his cassock and in the quiet sunniness of his little cul-de-sac discovering some of the most fundamental secrets of nature that his Creator had on offer — just the job for patron sainthood in genetics and there was the added bonus that he had a profile made for medals.

On the other hand there was the Devil’s Advocate: Professor Ronald Alymer Fisher, statistician and professional iconoclast, taking time off from cuffing his elders and betters to suggest that they re-read Mendel’s paper, this time using finger and moving lips, because the good monk’s data had all the hallmarks of being fiddled. No cassock, and his suit in the popular photograph suggests the aftermath of a night’s ratting. He had the gall to suggest that most of the features of Mendel’s genetical system could have been arrived at by abstract thought and as for medals, well in profile he had a face like a Maltese terrier . . .

Even the history of Mendel’s paper is unsatisfactory. It was published in 1865; 40 pages, read in two sittings, a month apart, to a tichy local society for the study of natural science and for the next 40-odd years it was accorded the equivalent of a footnote in biology. In 1900 it surfaced and its import became obvious. Mendel underwent habilitation and his results were brandished about by the pro-Darwinians in support of their stance. (This led to some bewilderment in the ranks: the anti-Darwinians were doing the same thing.) 1924 saw a biography of Mendel appear, written by one Iltis, whose father practiced medicine in Br¨unn when Mendel was alive. Iltis also interviewed Mendel’s gardener, of which more anon — and yes, since you ask, it is important.

Then, in 1936, Fisher published his paper.

This resulted in some embarrassment among biologists, because many had read: 

Mendel, G. (1865). Versuche ¨uber Planzen-Hybriden. Verhandlungen des naturforschenden Vereines in Br¨unn 4, Abhandlungen 3-47.

perhaps not as a book at bedtime, but in any event without noticing anything suspicious. (There was also the chronic pruritus brought on by having anything pointed out by an egregious smartar — uh, cleverclogs, like Fisher, who was a statistician1 and wouldn’t have known a pea plant from a triffid . . . )

When Fisher submitted his paper for publication, he enclosed a letter which subsequently appeared in print. Certain biologists with their own teeth ruined several layers of enamel upon reading: —

. . . I cannot help it if circumstances proceed to emphasise so strongly my main point, that Mendel’s own work, in spite of the immense publicity it has received, has only been examined superficially, and that the rediscoverers of 1900 were just as incapable as the nondiscoverers of of 1870 of assimilating from it any idea other than those which they were already prepared to accept. I suppose the real mystery is how science manages to make any progress at all.

So what was it that was niggling Fisher? Well, if you’re curious, we’ll go for a mooch through the peas. However, before we start, let’s, um, resolve to stay away from those large, technicolour plants that are rattling to each other. They’re not peas. 

Fisher’s Niggle in a Nutshell

I’ve checked the statistical method.

I’ve checked the mathematics.

Mendel’s data are an excellent fit

to a numerical ratio

that is simply not correct.

To finish off his argument, Fisher anticipates an obvious question: is it possible that Mendel, unwittingly hit an, er, extreme, but, well, fortuitous case? Huh! said Fisher; the probability of hitting Mendel’s results is less than 5%, and (reaching for the salt) this isn’t the only time such an er, extreme, but, well, fortuitous case occurs — there’s another one later in the paper.

Fisher wrote that when he began looking over Mendel’s paper, he “had not expected to find the strong evidence which has appeared that the data had been cooked” and even before he concluded his own paper, he was musing about what could have produced these suspect results. After publication, others took up the grail and, in consequence, Mendel’s life, his data, his techniques and even his motives were subjected to a thoroughgoing dissection. To be fair, everyone took the cue from Fisher, who continued to write on the matter: differentiate between data had been cooked and data had been consciously cooked by Mendel.

Not much is known about the motives of those who wrote on Mendel’s behalf. Defence of a Christian holy man? Committment to statements, perhaps not by them, but nonetheless in print and endorsed by them? Reluctance to label anyone a charlatan unless it was truly merited? There’s an obvious one: genetics and evolution were young sciences in 1936 (they were already developing the technological polysyllabic vocables so necessary for respectability and to keep the layman at bay). Neither would profit by having Mendelism synonymous, literally, with shell-and-pea artistry.

It’s interesting to dawdle through the motley speculations that were produced to explain the singularity of Mendel’s data. There are three disparate categories.

Category 1: The data are not precisely Mendel’s. What they are precisely are those of “some assistant who knew too well what was expected.” The monastery’s gardener was Josef Maresch. He was an old man by the time he was interviewed by Iltis (Mendel’s biographer) who subsequently wrote “Unfortunately Maresch was of bibulous inclinations (Mendel, we gather, had rather a poor opinion of the man), and this failing had played havoc with his memory.”

In other words, Mendel had expectations for his experiments and was mug enough to mention them to the obliging gardener-perhaps-cumturpsnudger who was to record the data.

Well, it’s a possibility. Fisher had no doubt that this happened. That Man Mendel 6

Category 2: With the benefit of hindsight, an honest mistake. As Sewell Wright (1966) put it: — Mendel was the first to count [genetic categories] at all. It is rather too much to expect that he would be aware of the precautions now known to be necessary for completely objective data. Sewell Wright cites a famous case of 15 trained observers given 532 kernels of corn to sort and count. And the “extraordinary” variation they produced. 

As Fisher (1936) put it: — One natural cause of bias is the tendency to give the theory the benefit of the doubt when objects such as seeds, which may be deformed or discoloured by a variety of causes, are being classified.

As a certain student put it:

Class (a): Round seeds

Class (b): Angular seeds

Class (c): Round, but if you hold it this way, there’s these knobs . . . it could be angular — well, fat angular . . . (Pause) . . .We could do with a few more angulars . . .

Well, it’s another possibility. It can’t be the entire story, though, because such a bias could only occur in quantitative measurements. There are qualitative characters present as well and “the bias seems to pervade the whole of the data” (Fisher) (again).

Category 3: Mendel had some grounding in mathematics and the laws of probability. He knew he would encounter the occasional extreme departure from expectation (in some of his experiments where he expected ratios of 2:1 he reported figures of 43:2, 14:15, 32:1 and 20:19 without a tremor). He was demonstrating to an audience of statistical innocents. Under these circumstances some tidying of the figures was necessary and excusable.

Yes, and Neanderthal Man used serviettes.

This is the argument — alright the state of mind — that has been attributed throughout the history of science, albeit behind various sets of false whiskers, to Ptolemy, Pythagoras, Lysenko and, recently, to Cyril Burt: being so convinced of the righteousness of your theory that you consider any fudging of figures is justified if it gets the theory established as a scientific truth. After considering it with respect to Mendel it would have to be rejected for lack of any evidence whatsoever.

However, if you want to dwell on it, consider an obverse: that with his grounding and knowledge etc., Mendel would also know it’s possible to encounter cases that agree very, very closely with expectation and he may, therefore, have been reporting such a case, with or without the tremor.

So we arrive at the far side of the pea patch. It should be mentioned that Mendel attempted later to duplicate his experiments on another plant species. This time there was no doubt about his results — they were disastrous. It’s been argued that this was evidence not so much of further lack of taste as questionable ethics on the part of the Almighty, who could have Moved in a Mysterious Way to tell Mendel of a peculiar sexual quirk of this plant. This quirk invalidates pollinating techniques . . .

Finally, honourable mention must be made of the good townspeople of Br¨unn. Just after 1900, an international committee of scientists wished to erect a memorial to Mendel in the town of his historic experiments.

The immediate objections raised by the pastoral gentlefolk were twofold:

1. We’re not letting any memorial go up to someone who wears his collar like that, and

2. In the klosterplatz? Where it will interfere with the local fair?

Ah, yes, the local fair. Where you can mooch through the stalls, taking deep breaths of the rustic atmosphere, haggling while you point out the faults of the local produce.

You should, for example, be able to buy these peas for less than these, because these look like they contain funny seeds. Look, they’re not spherical at all — they seem to have corners on them . . .