Introduction to Karl Ernst von Baer

An introduction to Baer

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(The study of the reproduction and development of organisms: Preformation versus epigenesis)

A question posed by Aristotle was whether the embryo is preformed and therefore only enlarges during development or whether it differentiates from an amorphous beginning. Two conflicting schools of thought had been based on this question: the preformation school maintained that the egg contains a miniature individual that develops into the adult stage in the proper environment; the epigenesis school believed that the egg is initially undifferentiated and that development occurs as a series of steps. Prominent supporters of the preformation doctrine, which was widely held until the 18th century, included Malpighi, Swammerdam, and Leeuwenhoek. In the 19th century, as criticism of preformation mounted, Karl Ernst von Baer, an Estonian embryologist, provided the final evidence against the theory. His discovery of the mammalian egg and his recognition of the formation of the germ layers out of which the embryonic organs develop laid the foundations of modern embryology.
(From Britannica)
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Two of the greatest figures in the 19th century biology - Charles Darwin and Karl Ernst von Baer - have been established two opposite approaches to biology.

For Darwin, biology is based on the study of phylogeny.
For Baer, biology is based on the study of ontogeny.

For Darwin, the source of perfection is outside, in the environment.
For Baer, the source of perfection is inside, in the organism.

Darwin paid major attention to microevolution and lower taxa.
Baer paid major attention to macroevolution and higher taxa.

For Darwin, the evolutionary changes are primarily genetic.
For Baer, the evolutionary changes are primarily epigenetic.

Karl Ernst von Baer studied in Tartu University, where his teacher was Karl Friedrich Burdach - the scientist who has been coined the term 'biology' in 1800. Scientometric analysis has shown that Baer's knowledge about the contemporary achievements in science, and his correspondence with other scientists were wider, and his library bigger than that of Darwin. They represent different (anglo-american versus continental) cultural traditions.

In addition to his works in biology, and notably in embryology, Baer made a great impact on establishing the modern anthropology, and he wrote many influential works on geography. More.

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