Hans Spemann
Walter Sutton
Oswald Avery
Francis Crick
James Watson
Paul Berg
Stanley Cohen
Herbert Boyer
Kary B. Mullis
Steen Willadsen
Ian Wilmut
Keith Campbell
Richard Seed

Hans Spemann, a German embryologist, is one of the original pioneers of modern embryology, and one of only two embryologists to ever be awarded the Nobel Prize. His studies focused upon the differentiation of embryo cells during an organism's development.

Spemann, born in Stuggart, Germany in 1869, attended the University of Heidelberg and the University of Munch before earning his Ph.D. in botany, zoology, and physics at the Zoological Institute of the University of Wurzberg in 1895. Spemann's fascination with embryology did not begin until after his college years, when during the winter of 1986 he read August Weismann's book The Germ Plasm: A Theory of Heredity as he sat isolated in a sanitarium, recovering from tuberculosis.

In 1902 Spemann, ingeniously using a stand of hair as a noose, successfully split apart the cells of a two-celled salamander embryo, and obtained a normal salamander from each individual cell. His work disproved August Weismann's theory that cells lose genetic information with each division. Also from his 1902 work, Spemann deduced that at a certain stage in development, called determination, the cells of an organism's embryo become differentiated.

In the late 1920's Spemann continued his work with salamanders. He transferred the nucleus of a sixteen-cell embryo to a single salamander embryo cell with no nucleus. The cell took up the nucleus and developed into a normal salamander. With this process, Spemann completed one of the first cloning experiments using the nuclear transfer method. In the 1938 publishing of his results, entitled Embryonic Development and Induction, Spemann proposed the "fantastical experiment" of cloning an organism from differentiated or even adult cells using the nuclear transfer method. However, during his time, Spemann did not have the technology to complete his vision, and cloning as he proposed it was not completed until the success of Robert Briggs and Thomas King in 1952.

In 1935, Spemann received the Nobel Prize in medicine for the organizer effect, a case in which a part of an embryo, when transplanted to other regions of the embryo causes a change in the surrounding tissues.

In addition to his influential embryology discoveries, Spemann's unusual strictness in the creation of precise laboratory instruments led to numerous advances in microsurgical equipment during his time.

Timeline: Spemann Splits an Embryo
Timeline: Spemann Performs First Nuclear Transfer
Timeline: Spemann Proposes Cloning

Web Link:
Biography of Hans Spemann

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