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Preface

There appeared recently in Physics Today, a journal dedicated to providing news to the members of the American Physical Society, a letter that, in part, describes the surprise with which the author discovered that Gregor Mendel had worked within the traditional mode of his field when he carried out his research on the rules of genetic inheritance in garden peas. [1] This reaction to a visit to the Mendel Museum in Brno, Czechoslovakia suggests a mindset that many people have about Mendel and his work -- that he was ``an isolated genius who worked out the laws of heredity in isolation in a monastery in Moravia''. On the other hand, many botanists are just as sure that Mendel formed part of a continuum of research on plant hybridization that continued for more than a century. These mutually contradictory opinions emphasize the fact that today, a century and a quarter after Mendel published his analysis of experiments on the genetic behavior of varieties of garden pea plants, Pisum, there appears to be anxiety or uncertainly or confusion as to what actually did transpire in the Mendel Affair. Why did his paper languish, unheeded, for 35 years before it was finally read with comprehension by the botanists? In fact, it was another 35 years later, 70 years after Mendel's paper was published, that someone, Ronald Aylmer Fisher -- a mathematical statistician -- felt impelled to write a paper that attempted to answer, with reasonable mathematical sophistication, the question, ``What did Mendel really do, and how did he do it?'' Fisher concluded that there is some reason to question the plausibility of the data Mendel produces of being a random sample.[2] I have seen the Mendel affair used as an example of what happens if one does not communicate clearly in a written paper. The paper was, in fact, a transcript of a talk given to a professional society. Granted, this limited the length of the paper, but certainly not its intelligibility. It gives it, rather, an interesting didactic quality. I have heard the Mendel affair cited as an example of what happens when one publishes in an obscure journal. But the paper was distributed widely from Russia to the United States, and it was readily available to those movers and doers who eventually understood the importance of its message. It is important to realize that Mendel wrote precious little more after that first paper. In fact, he spent the succeeding 8 years in a futile research on the genetic behavior of a plant that fascinated Carl Naegele, the Swiss botanist who held sway over the field of plant genetics at that time. Mendel worked hard to satisfy Naegele's curiosity about this hawkweed plant. Botanists now know why Mendel's effort was to no avail, and the effort he made in the quicksand of that problem finished him quite as effectively as if Naegele had mugged him! A voluminous correspondence accompanied this research, and Naegele preserved Mendel's letters to him. But, incredibly, Naegele did not make a sufficient effort to alert his own students to Mendel's paper, and it was left to one of them, Carl Erich Correns, to duplicate Mendel's results and conclusions some 35 years later -- and then accidentally discover Mendel's original paper on the matter.[3] Look at the chaotic picture these pieces of information make.

• Mendel's research was a continuous development of preceding research, yet its eventual widespread application led to a discontinuous jump in the understanding of botanists, and geneticists -- as some came to be called -- in the process of genetic inheritance.
• Mendel published his results in an unpersuasive manner in a journal of limited circulation. Yet he interacted vigorously for years with the then leading light in botanical genetics. In spite of this intimate relationship with Mendel, Naegele never saw it fitting to mention Mendel's research on peas in any of his own publication, or even to emphasize its importance to his own students!
• Mendel's data was amassed over more than 8 years and involved counting, for example, some 60,000 pea seeds. Yet by Fisher's analysis there are reasons to question the objectivity of his data. No one really questions the seminal nature of Mendel's work, but there does appear to be a disproportionate amount of the literature devoted to minimizing his objectivity.

What transpired in the Mendel affair is much more complicated than these items could lead one to believe. But complexity alone is not sufficient reason to dwell on the affair. Rather, it is worth looking at the affair from our present perspective since this tragic disaster that happened to Mendel is a parable, that allows one to reach an understanding, or a fable, from which one can extract morals, that are too important to be ignored today. But morals are best drawn after the fable is told, so these issues will be left for examination later. For now we sketch the drama that Mendel faced as a professional physicist when he undertook his research -- the essence of the problem, the tools needed, and the nature of the barrier that separated him from the observationalists, or naturalists -- the botanists -- who comprised his proper audience. Stated in terms of topics in the format that was used above, the following presentation will suggest that:

• Mendel saw, with great perspicuity, that fruitful research in the basic rules of genetics required that large amounts of data be taken, and that data be reduced with incisive statistical analysis.
• The characteristics to be followed through a genetic tree must be carefully chosen as those capable of being analyzed statistically, given the possible sources of the data.
• This imperative of Mendel to find a proper experimental medium with which to obtain the required data bank for statistical analysis, separated him quite clearly from other contemporary researchers. The distinction between Mendel and the naturalists with whom he would have had to interact appears to be cultural. This concept of a cultural chasm will have to be considered in detail later. The twentieth century has managed to replace with the title, scientist, the descriptive distinction that the names botanist, physicist, chemist, etc. evoked.
• In other words, Mendel looked for a good experiment that he could try to understand using statistics, instead of the more usual pattern of trying to understand what might appear to be a good experiment that happened to come in hand.
• Certainly Mendel's intuitive understanding of binomial statistics places him apart from his contemporary peers in genetic research.

Statistical packages of software for personal computers are so readily available that will be possible to illustrate much of Mendel's experiments in the presentation that follows.