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made the first series of experiments by hybridizing two forms with a pair of
contrastive traits. For instance, crossing a long-stem pea plant with a short-stem
one would produce the first generation of offspring (the hybrids), in which all plants
possess a long stem. Then he made the first generation of offspring self-fertilize and
got a ratio of 3 long stem to 1 short stem in the second generation. Mendel called the
traits of the majority of the offspring “dominant” and the minority traits “reces-
sive.” He used the sign A to denote the dominant traits and a the recessive; he then
expressed the experimental results as a symbolic formula: A +2 Aa + a (Mendel
1966 , p. 16). The result has been interpreted as empirical evidence for the first law
of heredity.
Mendel conducted the second series of experiments by hybridizing two forms
possessing a combination of two pairs of contrastive traits—for example, long
stem with axial flowers and short stem with terminal flowers. Using the same
procedure as in the first series of experiments, Mendel obtained a second “mathe-
matical formula”: AB + Ab + aB + ab +2 ABb +2 aBb +2 AaB +2 Aab +4 AaBb ,
in which A denotes the dominant of the first pair of contrastive traits and B that of the
second pair; a denotes the recessive of the first pair and b that of the second (Mendel
1966 , p. 20). This result has been interpreted as empirical support for the law of
independent assortment. Therefore, Mendel was credited with the discovery of the
two fundamental laws of heredity.
When he finished his work, Mendel wrote a paper titled “Versuche ¨ber
Pflanzen-Hybriden (Research on plant hybrids)” to discuss the result and published
it in a local journal, Proceedings of the Natural History Society of Brno, in 1866.
The paper with his “discovery” was neglected for 34 years, until 1900, when three
botanists—Hugo de Vries, Carl Correns, and E. Tschermak—rediscovered the laws
of heredity and Mendel's paper. Almost all scientists and authors of textbooks
believe this story, as do many historians of biology (Mayr 1982 ; Magner 2002 ;
Carlson 2004 ). It is the orthodox view of Mendel's discovery. Some historians of
biology began to challenge this orthodox view in the 1980s. They attributed
Mendel's work to the old tradition of breeding and hybridization experiments rather
than the new genetics. They questioned whether Mendel was really a Mendelian,
arguing that Mendel had no idea of a gene or paired factors and presented no law of
heredity in his 1866 paper. What concerned Mendel was not the problem of how a
trait is transmitted from parents to offspring but whether new species could arise by
hybridization (Olby 1985 ; Bowler 1989 ; Corcos and Monaghan 1993 ). The histo-
rian Bowler ( 1989 ) reconstructed the Mendelian revolution based on Kuhn's theory
of scientific revolution. 7 Bowler placed Mendel's research and experiments under
7
Bowler ( 1989 , p. 15) emphasized the importance of the paradigm concept to the history of
science: “The fact that paradigms are entities with definite beginnings and ends turns the history of
science into a genuinely historical discipline, since it implies that one can only understand the
science of a past era by trying to think oneself into the conceptual scheme of the then-dominant
paradigm.” In Bowler's view, the invention of Mendelian genetics (i.e., the general acceptance of
Mendel's laws of heredity) required the construction of a new conceptual framework of “hard
heredity.” Therefore, Mendel's contemporaries naturally failed to understand the significance of
his findings to heredity.
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