Wrinkled v. Round

Andrew Berry

  • A Monk and Two Peas: The Story of Gregor Mendel and the Discovery of Genetics by Robin Marantz Henig
    Weidenfeld, 288 pp, £14.99, June 2001, ISBN 0 297 64365 7

A report in Science magazine in 1990 exposed the absurdity of our publish-or-perish academic culture. It focused on citation rates – the frequency with which my article is referred to by my colleagues, or indeed by me – which serve as an index of the impact of a particular piece of research. Because of the plethora of obscure or regional journals in circulation, the study was confined to the top 5 per cent or so of scientific journals, some 4500 of them. It asked what proportion of all articles published in those journals between 1981 and 1985 were never cited, not even once, in the five years after publication. The answer was astonishing: 55 per cent had never been cited, not even by their own authors. And papers not cited within five years of their first appearance are unlikely to be cited subsequently. Over half the academic literature is still-born.

One cannot help wondering whether in these enormous drifts of academic chaff lurks the occasional unsung study of great importance. The popular perception, though, is that academia is about as meritocratic as human enterprises get – that, in short, a good idea will out. This, however, was not true, at least not for a long time, in the case of Gregor Mendel, the Moravian monk whose experiments on pea plants laid the foundations of genetics. When Mendel published his results in 1866 they were ignored by the scientific community, and he died in relative obscurity in 1884. Only in 1900 was his work ‘rediscovered’ by three botanists, each supposedly stumbling on it independently. In 1906, William Bateson, the most forceful champion of Mendel’s work in Britain, dubbed the new science ‘genetics’.

Those 34 years of obscurity have fascinated historians of science. Why was such a major advance overlooked for so long? That Mendel published in German in a relatively obscure journal may have had something to do with it. Maybe he was out of sync with the era’s biological agenda: evolution was the hot topic, not the nuts and bolts of how characteristics were transmitted from parents to offspring. Maybe professional biologists disregarded Mendel’s work because he was an amateur. Maybe he was simply ahead of his time, especially in his marriage of statistics and experiment. Maybe Mendel himself failed to appreciate the significance of his work. Maybe he did appreciate it but was not aggressive enough in pushing his findings. Indeed, the famous paper of 1866 is not a full report of the experiments he had conducted but rather a write-up of two lectures he had delivered at his local natural history society the year before.

Revisionists have suggested that Mendel did not have as full an understanding of genetic mechanisms as modern textbooks suggest. They claim that Mendel’s heroic status was partially manufactured by Bateson and other early geneticists in order to provide their new science with an appealing founding mythology.

One reason many aspects of Mendel’s life and work are controversial is that the documentary record is so poor; and controversy thrives in the absence of information. His scientific correspondence consists solely of a handful of letters exchanged with the botanist Karl von Nägeli in Munich. Documents relating to his personal life are even scarcer, and typically unenlightening. He wrote a ‘short summary of his life’s history’ in 1850, to accompany his application to sit a teacher’s certificate exam. This brief yet florid document, which opens ‘Praiseworthy Imperial and Royal Examination Committee’ and in which Mendel refers to himself in the third person as ‘the respectfully undersigned’, is the major source of information on his early life. The few letters to relatives that survive either concentrate on current events – like the Austro-Prussian War of 1866 – or are utterly mundane: ‘There has been a lot of snow during the last few days.’ (Darwin, by way of contrast, has left very little to the biographer’s imagination: his surviving correspondence runs to some 15,000 letters.)

Born in 1822 in the Silesian village of Heinzendorf, in what is now the Czech Republic, Johann – he adopted the name Gregor on taking monastic orders – Mendel was the only son of a peasant farmer. He excelled in the village school and was sent away to the Gymnasium in Troppau. Times, he relates, were hard: ‘due to several successive disasters, his parents were completely unable to meet the expenses necessary to continue his studies, and it therefore happened that the respectfully undersigned, then only 16 years old, was in the sad position of having to provide for himself entirely.’ And things only got worse when he went on to the Philosophical Institute in Olmütz:

he made repeated attempts . . . to offer his services as a private teacher, but all his efforts remained unsuccessful because of lack of friends and recommendations. The sorrow over these disappointed hopes and the anxious, sad outlook which the future offered him, affected him so powerfully at that time, that he fell sick and was compelled to spend a year with his parents to recover.

This was the first of Mendel’s several mysterious bouts of ill health.

In 1843, he entered the Augustinian monastery of St Thomas at Brünn (now Brno). Obscure though it may be today, Brünn then was no intellectual backwater, and nor was the monastery monastic in the sense of any cloistered withdrawal. Under its liberal and intellectual abbot, F.C. Napp, it had become a major research centre in a town already renowned for its contributions to industry and agriculture. And, by the standards of the era, Mendel was positively cosmopolitan: in 1862 he joined a group of Moravians who travelled to London to visit the International Exhibition. The popular notion of him as a lonely, cowled figure bent over his pea plants, quietly effecting a scientific revolution in complete isolation, is way off the mark.

After a disastrous spell as a parish priest, Mendel became a teacher, initially in Znaim, and subsequently at Brünn’s Technical School. He had found his métier. Every reference to his teaching is laudatory, whether from colleagues or pupils. Hugo Iltis, himself a local schoolteacher, sought out the still-living among Mendel’s pupils when preparing his 1924 biography, the first major work on Mendel (and perhaps the most revealing account of him). The recollections he recorded are embarrassingly saccharine: ‘He was such a good cook that he could make any intellectual food nutritious and tasty, no matter whether the subject was zoology, botany or physics.’

Despite his obvious aptitude, Mendel lacked the formal qualifications required of a Gymnasium teacher and sought to make amends by taking the necessary exams in Vienna in 1850. His first attempt to pass – arguably the lowest point of a career that had seen a few low points – is, ironically, one of the few well-documented episodes of his life. The exam consisted of three phases: essays prepared over a number of weeks, a viva voce and a written paper. One essay was well received, but the second, on geology, failed to impress the examiner: ‘The candidate has, indeed, written about many things, briefly in many cases, but neither concisely nor clearly.’

It was his performance in the written paper that ultimately torpedoed him. Even Iltis, whose biography is close to hagiographic, is unsympathetic: ‘One cannot but realise that the most kindly of examiners would have been compelled to withhold his approval from the candidate’ on the basis of Mendel’s answer on the classification of mammals. Iltis assumes that ‘Mendel, really knowing nothing about the subject, wrote in his perplexity whatever happened to come into his mind.’ He fared better in the viva voce: ‘It was plain,’ reported the examiners, ‘that he was devoid neither of industry nor of talent’; but he had failed.

All was not lost, however. Thanks to the intervention of Abbot Napp, Mendel was able to take the exam again, after spending some time at the University of Vienna. These two years in Vienna, 1851-53, hold the key to Mendel’s intellectual development. He learned plenty of biology but it was doubtless his exposure to high-powered physics that had the greatest impact. His teachers were Christian Doppler (of Effect fame), and Andreas von Ettingshausen, who had published extensively on combinatorial analysis – essentially the mathematics of putting together multiple objects in different orders or permutations. University records indicate that Mendel distinguished himself most in physics. His exposure to statistical and combinatorial thinking allowed him later on to make sense of the patterns he observed from generation to generation in his pea plants. Mendel’s work was an early instance of what has become a frequent phenomenon in biology: insight into previously intractable problems acquired by using rigorous methods borrowed from the physical sciences.

Whatever the virtues of Mendel’s Vienna education, he again failed the certification exam in 1856. By then he was back in Brünn at the Technical School, and there he stayed, without ever formally qualifying, until, in 1868, he became Abbot of St Thomas’s. He carried out his experiments on peas between 1856 and 1863.

Mendel’s experiments were brilliantly conceived and painstakingly executed. He was exceedingly careful in his choice of what to study: pea plants are easy to raise and can be both out-crossed or self-fertilised, and he chose to study only characters – wrinkled v. round peas, for example – that are discrete and not likely to grade into each other. But he was lucky as well. When looking at pairs of characters – wrinkled/round and yellow/green, for example – their chromosomal locations are critical. When a pair is found on the same chromosome, the outcome of a cross is much less predictable than when it is on different chromosomes. Mendel, who died a year after chromosomes were first described, chose traits that happened to be on different chromosomes.

The British geneticist R.A. Fisher once suggested that Mendel might have pushed his luck rather further than is scientifically kosher. His results were too good: they conformed too well to expectation. Toss a coin 1000 times, and you expect to get 500 heads. But the probability of getting exactly 500 is rather low, given the inevitable variation associated with a chance process. Mendel came up each time with the genetic equivalent of 500, or very close. Fisher’s comment has spawned responses ranging from the charge that Mendel did not in fact do any experiments, but fabricated all his data, to abject displays of defensive adoration. Was he a cheat? No. The evidence that he carried out the experiments as he described them is undeniable. He may indeed have weeded out some of the more aberrant data because he suspected accidental contamination of his crosses. And, as Fisher also pointed out, Mendel’s 1866 paper was a written version of two public lectures, not a formal scientific presentation. A lecturer with a point to make is likely to pick the most powerfully illustrative examples available rather than presenting all the pertinent data.

Mendel’s luck ran out in the next phase of his scientific career. On the advice of Nägeli, his one contact among ranking scientists, he attempted to reproduce his pea results using another plant, hawkweed. He could thus test the generality of his results: would they apply only to peas? Iltis notes that Nägeli himself was working on hawkweed. ‘With the egoism of so many enthusiastic scientists, he had become accustomed to regarding his own aims as more important than anyone else’s, and was only inclined to give sympathetic help in such researches as might contribute to his own.’ One of the more pathetic episodes in Mendel’s story bears this out. He sent Nägeli ‘140 carefully docketed packets of seeds’, in the hope that Nägeli would replicate his pea experiments. He did no such thing. Hawkweed, in marked contrast to the pea, turned out to be a poor choice of species for genetic study, and Mendel’s results were confusing, and apparently at odds with the pea data. It’s perhaps not surprising that, in his busy later years as Abbot, he forsook plant breeding for beekeeping and meteorology. His published account of the freak tornado that struck Brünn in 1870 – breaking 1300 panes of glass in the monastery church alone – includes some sophisticated theorising about its probable cause. He concludes: ‘We have indulged in multifarious suppositions about it, but must concede, in the end, that with the best will in the world we cannot get beyond airy speculations, built up out of air, and established upon an equally unstable foundation.’

Given the general lack of documentation, it is remarkable that we have any sense at all of what Mendel was like. Surprisingly, he seems to have been rather puckish. He would delight in promising to show off ‘his children’ to visitors to the celibate confines of the monastery. These would turn out to be his pea plants. His portliness eventually hampered his fieldwork because hill-climbing had become ‘very difficult for me in a world where universal gravitation prevails’. His doctors prescribed tobacco to keep his weight in check, and he obliged them by smoking twenty cigars a day, the same number as Winston Churchill.

Though engagingly written, Robin Marantz Henig’s biography adds little that’s new. It is also guilty of perpetuating some colourful but misleading myths. One pertains to the substantial body of scholarship on the relationship – or lack of it – between Mendel and Darwin. Darwin invented his own specious theory of inheritance, and historians of science have wondered whether he was aware of Mendel’s work. Had he been, would a Victorian ‘eureka’ moment have taken place in the Down House study? As it happens, the marriage between Darwinism and Mendelism occurred only in the 1930s. Henig reports that Darwin owned a copy of Mendel’s paper, which adds a so-near-and-yet-so-far frisson to the story. Unfortunately Henig is wrong: Darwin did not in fact own a copy.

The question remains: why the 34-year lag? On balance, and with all due respect to the revisionists, who see Mendel’s reputation as an early instance of scientific hype, I like Iltis’s view that ‘the time was not ripe.’ Mendel, he believed, was simply ahead of his time. With his training in physics, Mendel brought a sophisticated quantitative angle to biology, a science that was at the time almost wholly descriptive. It’s hardly surprising that contemporary biologists failed to understand what he was going on about. This is borne out by a detailed look at those years of neglect. Henig reports that Mendel’s paper was cited 22 times during that period: his work was known but its significance was not recognised. Mendel was not so much uncited as simply unappreciated.