Hereditas 107: 103-105 (1987)

What did Mendel say about evolution?

PAAVO VOIPIO

Department of Biology, University of Turku, Finland

VOIPIO, P. 1987. What did Mendel say about evolution? - Hereditm 107: 103-105. Lund, Sweden. ISSN 0018-0661. Received November 27,1986

The text-books in General Biology and Genetics traditionally are restricted to Mendel’s contribution to the fundamental elementary laws of genetic recombination. This means that some 20 per cent of his text is not covered by the discussion generally given. What Mendel really said in these neglegted chapters is the prin- cipal subject of this paper.

Paavo Voipio, Department of Zoology, University of Helsinki, P. Rautatiekatu 13, SF- 00100 Helsinki 10, Finland

After the “rediscovery” of Mendel, several reprints were taken from his publication. One, translated by Bateson, appeared in England 1901, and two others, in Germany. Of the latter the better known was printed in “Ostwald’s Klassiker der Exakten Wissenschaften” in 1901 and edited by Erich Tschermak, one of the discoverers of Mendel. The English translation now appears as an appendix in SINNOIT-DUNN-DOBZHANSKY’S book “Principles of Genetics” (1958), and the edition by Tschermak saw its 6th printing already in 1940. Both have thus been obtainable rather easily (the German edition also contains the latter publication of Mendel from 1869, which dealt with the experiments in Hiera- cium) .

But how many people have really read Mendel’s “Versuche iiber Pflanzen-Hybriden” or “Experi- ments in Plant Hybridization”, and how carefully?

When the extraordinary contribution of Mendel is related in the textbooks, just the experiments on hybridization, of course, are surveyed in them and nearly in ecstasy. By coming across the original paper (or its reprint) one in all probability con- centrates upon or simply confines oneself (e.g., FEDERLEY 1922; DUNN 1965) to the very paragraphs or chapters where the experiments and their results have been presented. But, besides, there are in Mendel’s paper a short introductory chapter (“Ein- leitende Bemerkungen”, Introductory Remarks) and also an extensive concluding chapter (“Schluss- bemerkungen”, Concluding Remarks).

Mendel and evolution theory In his introductory remarks Mendel states that not one of the experiments so far made had been carried out to such an extent as to make it possible to deter- mine the number of different types among the off- spring of hybrids and to arrange these types accord- ing to their separate generations and, finally, to ascertain their numerical relations. In these words hides the whole splendid idea of the ingenious method of Mendel from the genetical point of view. After having stated, in addition, that it requires indeed courage to undertake a task of such an extent, Mendel adds that “this, however, seems to be the only right way of finally reaching a solution to a question the importance of which for the evolu- tionary history of organic forms must not be under- estimated” (“indessen scheint es der einzig richtige Weg zu sein, auf dem endlich die Losung einer Fra- ge erreicht werden kann, welche fur die Entwick- lu,ngsgeschichte der organischen Formen von nicht zu unterschatzender Bedeutung ist”, loc. cit. p. 4; italics mine)‘).

It seems that, to Mendel, the cardinal question in- spired by his results is associated just with the evolu- tionary history of organic forms. This view still strengthens when one reads the last chapter

- ’) In this and the following German citations I follow the original paper by MENDEL (1865).

104 P. VOIPIO Hereditas 107 (1987)

(Schlussbemerkungen) of his paper. Mendel states there that some of the offspring of the hybrids re- main perfectly like the hybrid and continue constant in their offspring (“bei einigen aber b 1 e i b e n s i e d e r H y b r i d e v o l l k o m m e n g 1 e i c h und pflanzen sich unverandert fort”, loc. cit., p. 38). Though Tschermak calls attention to the fact that the difference between hybrids of separate species and those of different varieties has remained unclear here, the citation clearly reflects Mendel’s tendency to regard hybridization as a factor which creates something new. This idea becomes fully clear later when Mendel refers to Gaertner’s and Wichura’s constant and fertile hybrids propagating like pure species, and states that “this circumstance is of particular importance to the evolutionary histo- ry of plants, because constant hybrids attain the status of n e w s p e c i e s”. Mendel realized that it is speciation that matters here, and that the hybrid, like any other independent plant species, remains stable in its offspring (“. . . die Hybride, wie jede andere selbststandige Pflanzenart, in ihren Nachkommen constant bleiben werde”; italics mine).

As BRANNIGAN (1979) remarks, “this passage was clearly written by someone who appreciated the possibility of speciation via hybridization”. Mendel not only considered speciation possible along this way but also described the course of events through which the new forms arise and retain their quality, i.e., breed true.

The question left open by his predecessors gave Mendel the intellectual stimulus which induced him to enter into such a painstaking experimentation year after year, He was closely associated with the hybridist-tradition like Gaertner, Koelreuter and Wichura, all of whom had seen hybridization as a key for understanding speciation (BRANNIGAN 1979, p. 443). In this area, Mendel considered himself as having advanced farther than his predecessors. Brannigan’s analysis shows that Mendel was not, in the opinion of the hybridists of the time, revo- lutionary, but was made into such one 35 years later. The basic explanation of the genetic framework needed for the evolutionary theory has then created a totally new standpoint for regarding Mendel as revolutionary reformer.

Mendel and Darwin BRANNIGAN (1979) has also presented a rather inte- resting view on Mendel’s attitude to evolution theo-

ry. According to him (p.441) Mendel did not regard his work important in the context of Darwinian evolution. Some passages found in his correspon- dence with Nageli (of which Brannigan seems not to be aware) indicate that he also accepted the Darwinian theory of natural selection. In other words, the variants from which “the struggle of existence” selected the fittest were the results of hybridization (ILTIS 1951, p.32).

BRANNIGAN (loc. cit.) speaks of Mendel’s paper in singular, thus certainly referring to Mendel’s first paper entitled “Versuche uber Pflanzen-Hybriden” from the year 1865. Nowhere is Darwin mentioned in it. But in his second paper (MENDEL 1869) “Ueber . . . Hieraciumbastarde” Darwin has been mentioned once. In the discussion of the origin of constant hybrids, it is mentioned that “a famous Hieracium expert represents, in the spirit of Dar- winian doctrine, the point of view according to which these would derive their origin from the transmutations of species now extinct or still extant (loc.cit., p.49; orig. in German). With a view to our discussion following later, it is to be especially recognized that Mendel, in speaking of the accep- tance of Darwinian doctrine, decidedly puts it to the account of others.

Mendel had bought all of Darwin’s books to the library of the monastery, and the notations in Men- del’s handwriting show that he had become tho- roughly familiar with them (MOORE 1954, p.159; KRUMBIEGEL 1957). Their influence on an open- minded man as Mendel probably has been more profound than is generally known. There are some rather early statements, in the literature, about Mendel’s attitude towards evolutionary theory. One of these is the paper by X~~is(1951, pp.30,32) and another is the book by MOORE (1954). Both state shortly that Mendel accepted the evolution theory and, in addition, that he tried “to show a new and better explanation of how evolution takes

points out - though in a very cautious tone - that “one can well presume that Mendel stood, so far as it was possible in his time, on the basis of evolutio- nary thought” and adds that “too many single fea- tures point to his convincement about the possibility of transmutations of species” (loc. cit., p. 137; orig. in German). Mendel was, thus, perfectly aware of the evolutionary significance of his experiments on hybrids. The recent Mendel biography has taken notice of these aspects of Mendel’s writing in a colloquy held in Brno 1970 in a special session entitled “Mendel’s attitude to evolution” (see GED- ~ ~ 1 9 7 1 ; OREL 1971; SINOTO 1971).

place” (ILTIS lOC. Cit., p.32). Also KRUMBIEGEL( 1957)

Hereditas 107 (1987) WHAT DID MENDEL SAY ABOUT EVOLUTION? 105

Mendel and public opinion In his immediate neighbourhood, Mendel was su- spected - apparently not without reason,- of being a Darwinist (ILTIS 1951, p. 30). BRANNIGAN (1979, p.442) ponders why Mendel did not send his papers to Darwin, or to the other evolutionists in England of that time. Another circumstance, also pointed out by BRANN~GAN (loc.cit., p.443), is that Mendel only indirectly ties his research to the problem of evolution. He, namely, does not speak of his own work, but discusses the works of such researchers as Gaertner, Koelreuter and Wichura who all empha- size the importance of speciation through hybridi- zation. In the opinion of Brannigan, it is just this manner of discussing the results of others which veiled his own views upon evolution.

Though this explanation sounds quite natural, I think it is not fully satisfactory. It is to be remem- bered that Mendel as a catholic priest and a member of a monastery order could not proclaim himself as an adherent (follower) of Darwinian doctrine. Per- haps just for this reason he does not, in the introduc- tory chapter of his paper and in the “Concluding Remarks”, mention Darwin and his followers. Another explanation could be, as pointed out by BRANNICAN (1979), that Mendel was presenting, for the process of evolution, a new explanation in which selection was not involved.

In spite of this cautiousness, the stigma of being a Darwinist and free-thinker is said to have been attached to Mendel by the authorities. Thus, there may have been reasons for a certain reservedness. And this, in turn, possibly was the reason why Men- del never sent his publication to Darwin, Wallace, or Huxley.

Acknowledgements. - Professors Esko Suomalainen and 0th Halkka have read the manuscript in its different phases and effec- tively contributed to its improvement. I also wish to thank the former for having lent me a reprint of Mendel’s classic work, and professor Ossi V. Lindqvist for having fixed my attention upon Brannigan’s important article,

Literature cited BRANNNICAN. A. 1979. The reification of Mendel. - Soc. Stud. Sci. 9: 423454

DUNN. L. C. 1965. Mendel, his work and his place in history. - Proc. Am. Philos. Soc. 109 189-198

FEDERLEY, H. 1922. Gregor Mendel. En levnadsteckning t i l l 100-Arsdagen. - Fin. Verensk. Soc. Minnesreckn. Foredv. I (3):

GEDDA, L. 1971. Mendel’s attitude to evolution. - Proc. Gregor Mendel Colloq. Brno 1970. Folia Mendeliana 6: 157-159

ILTIS, H. 1951. Gregor Mendel’s life and heritage. -In Generics in the 20th Century (Ed. L. C . DUNN). The MacMillan Company, New York, p. 25-34

KRUMBIEGEL. I. 1957. Gregor Mendel und das Schicksal seiner Entdeckung. - Wissenschaftliche Verlagsgesellschaft, Stuttgart

MENDEL. G. 1865. Versuche iiber Pflanzen-Hybriden. - Verh. naturf Ver. in Briinn 4: 3-47 (Briinn 1866)

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MOORE. R. 1954. Man, Time and Fossils. The Story of Evolution. - Jonathan Cape, London

OWL. V. 1971. Mendel and the evolution idea. - Proc. Cregor Mendel Colloq. Brno 1970. Folia Mendeliana 6: 161-172

SINNO‘IT, E. V . , D U N N , L. C. and DOBZHANSKY. TH. 1958. Principles of Genetics (5th ed.). - McCraw-Hill Book Com- pany, New York

SINOTO, Y. 1971. Mendel’s two papers on Genetics. considered from the viewpoint of evolution. - Proc. Gregor Mendel Colloq. Brno 1970. Folia Mendeliana 6: 151-155

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