Though German by descent and language, Karl Ernst von Baer was born in Estonia, which was then one of the Baltic provinces of the Russian Empire. After studying at the nearby University of Dorpat in the Estonian city of Tartu, he went abroad to complete his education in Berlin, Vienna, and Würzburg, where one of his professors, Ignaz Döllinger, sparked in him an interest in the development of embryos.
In 1817, von Baer became a professor himself at Königsberg University, in what was then the capital of the German province of East Prussia, which bordered on Estonia. There he taught for nearly two decades, but spent increasing amounts of time lecturing in St. Petersburg, then the capital of Russia.
In 1834, he actually moved to St. Petersburg and became a member of the St. Petersburg Academy of Sciences, the Russian equivalent of the U.S. National Academy of Sciences. Although he had concentrated on embryology during his years in Königsberg, von Baer broadened his focus in St. Petersburg to include not only anatomy, but also ichthyology, ethnography, anthropology and geography.
One of the founders of embryology, von Baer discovered the notochord and the embryonic blastula. He also established the fact that mammals develop from eggs. His book, Über Entwickelungsgeschichte der Thiere (On the Development of Animals) surveyed available knowledge of animal development and served as the starting point for the field of comparative embryology.
Together with Heinz Christian Pander, he proposed the now accepted germ layer theory of development, in which three distinct systems of bodily structures are derived from three distinct layers of cells in the embryo, the ectoderm, mesoderm, and endoderm.
Von Baer is perhaps best remembered for his demonstration that the early embryos of even very distinct organisms can be quite similar. He showed that the various traits characteristic of particular types of organisms appear only later in the course of development.
This finding influenced Charles Darwin, who transferred von Baer's description of embryonic development to the context of evolutionary development (that is, Darwin proposed that generalized forms would evolve into specialized forms as evolution progressed).
Von Baer's comparison of embryos also did much to undermine the old idea that humans are sharply distinct from animals, since the embryos from which humans originate are so much like those of other animals.
In addition to his work in comparative anatomy and embryology, Von Baer made important contributions to arctic biology, meteorology, geology, and geography. For example, in geology, Baer's law, which states that, due to the earth's rotation, in the Northern Hemisphere, erosion occurs mainly along the right banks of rivers, and in the Southern Hemisphere, along their left banks.
He was a founder and the first president of the Russian Geographical Society, and a co-founder of the Russian Entomological Society. In 1837 he made an expedition to the island of Novaya Zemlya off Russia's northern coast. He also explored the Caspian Sea and the northern coast of Scandinavia.
Von Baer spent the last years of his life (1867–1876) in his native Estonia, at Tartu.
Major works: De ovi mammalium et hominis genesi (1827); Über Entwicklungsgeschichte der Thiere (vol. 1, 1828; vol. 2, 1837); Beiträge zur Kenntniss des russischen Reiches und der angränzenden Länder Asiens (1839).
Full name: Karl Ernst Ritter von Baer, Edler von Huthorn.
Karl Ernst von Baer's exact dates of birth and death: February 28, 1792 — November 28, 1876.
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