Encyclopedia of Evolution.pdf - Online Reading Center

ish priest but was not successful; and he failed the exam for
being a science teacher. He went back for more education, this
time studying physics and mathematics at the University of
Vienna. He was ordained and entered the monastery at Brünn.
He had been recruited to the monastery upon the recommendation
not of clerics but of a professor of physics at Vienna,
because the monastery, with greenhouses, a big herbarium,
and a library with 20,000 volumes, was looking not just for
a monk but for someone who would conduct agricultural
research. Several monks at Brünn were involved in research
with crop plants and livestock animals for the benefit of the
local peasant economy. The monastery supplied Mendel with
two full-time assistants to help with his research.
Mendel began his experiments with pea plants in 1856,
which grew into a study involving many thousands of plants, on
which he kept careful records of cross-pollination. In one case
he obtained 14,949 dominant to 5,010 recessive plants, a ratio
of 2.98 to 1, which is very close to the theoretical 3:1 ratio that
Mendel expected. In fact it was closer than scientists (or especially
genetics students in college biology laboratories) could
ever expect to get. Some historians have suggested that Mendel’s
results were influenced by what he was expecting to see.
Mendel presented his results at a meeting of the Natural
History Society of Brünn, and the published results were
Gregor Mendel, the monk who discovered the laws of heredity, holds a
plant. (Courtesy of James King-Holmes, Science Photo Library)
Mendel, Gregor
distributed to more than a hundred other scholarly societies
in Europe, including the Royal Society and the Linnaean
Society in England. His work went largely unnoticed, except
for a brief review by the German botanist Wilhelm Focke.
One leading botanist, Karl Wilhelm von Nägeli, believed so
strongly in blending inheritance that he concluded that Mendel
must be wrong and ignored his work. Nägeli’s 1884 book
about evolution and inheritance patterns makes no mention
of Mendel. Nägeli even suggested to Mendel that he study
hawkweeds, which Mendel did. Mendel did not find his 3:1
ratio in hawkweeds. Today scientists know why: The plants
reproduce without sexual recombination. Nägeli’s main claim
to fame today, therefore, is in ignoring, then misleading, the
“Father of Genetics.”
Mendel studied many other things, such as sunspots,
bees, and mice. In 1868 Mendel assumed a leadership role in
his monastery, which became embroiled in legal problems,
and this left him no time for research.
Mendel was not the first investigator to suspect that
inheritance proceeded in a particulate, rather than blending,
fashion. Pierre Maupertuis, director of the French Academy of
Sciences during the 18th century, had a surgeon friend, Jacob
Ruhe, who had six fingers, and whose family had several other
six-fingered members (polydactyly). Maupertuis said that traits
such as polydactyly must be passed from one generation as a
discrete unit rather than by blending. Besides the fact that his
ideas were ahead of their time, Maupertuis’s reputation was
skewered by the acerbic pen of the writer Voltaire.
Furthermore, Gregor Mendel was not the first investigator
to study the inheritance patterns of characteristics in peas.
According to geneticist Richard Lewontin (see Lewontin,
Richard), earlier scientists such as Alexander Seton and John
Goss in 1822 and Thomas Knight in 1823 observed segregation
of green and pale seeds in second generations of pea crosses,
the very species and trait Mendel studied. Louis Vilmorin in
1856 counted results from individual crosses, even reported the
same 3:1 ratios that Mendel saw. But these investigators did
not draw the conclusion of particulate inheritance that Mendel
did. Charles Darwin observed what we now understand to be
Mendelian patterns in his study of snapdragons, and he speculated
about particulate inheritance (“crossed forms go back …
to ancestral forms”) but did not take it any further.
Mendel died January 6, 1884, without ever knowing that
his work would prove important as the foundation for the science
of genetics. In addition, his work provided the key for
understanding how natural selection could work (see natural
selection; modern synthesis). Charles Darwin studied the
review that Focke had written of Mendel’s work but apparently
missed its significance. Mendel had a German translation
of Darwin’s Origin of Species but also apparently failed
to see the connection. If Darwin had realized what Mendel’s
work had meant, he might have been able to answer the challenges
of the engineer and scientist Fleeming Jenkin and other
skeptics and would not have wasted his time inventing the
now discredited theory of pangenesis.
Three botanists (Hugo de Vries, Carl Correns, and Erich von
Tschermak von Seysenegg; see DeVries, Hugo) rediscovered
Mendel’s work about 1900. About the same time, Walter Sutton,