Hermann Werner Siemens

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Hermann Werner Siemens (20 August 1891 in Charlottenburg – 21 December 1969 in Leiden[1]) was a German dermatologist who first described many skin diseases and was one of the inventors of the twin study.


Siemens studied at Berlin and Munich universities, receiving his doctorate in 1918. In 1929 he became chair of dermatology at Leiden in the Netherlands.[2]

In a break-through study, he published "Zwillingspathologie" (Twin Pathology) in 1924 which introduced the widely used "classical twin method." He was the first to not only use twins in a study (to determine the role of genes over environment in skin moles), but to distinguish identical from fraternal twins, and use the correct 100%/50% genetic similarity inferences regarding these groups.[3]

His influence on the invention of the twin study is not widely acknowledged, possibly due his support of the Nazi's eugenic policies. His book Foundations of Genetics, Racial Hygiene and Population Policy called for voluntary sterilization of "pathological persons" and later editions of the book included statements in praise of Hitler's ideas on racial hygiene.[4] However, by 1942, he had lost his chair at Leiden and was even temporarily held hostage due to his resistance to the German occupation policies. Not until after the war did he regain his faculty position at Leiden, which he held until retirement.[1]

During the period away from academia Siemens wrote a book about the ancestors of his father in law: Die Vorfahren von Friedrich von Müller, Munich, C.H. Beck, 1957 - 337 pages.

Diseases named after H.W.Siemens:[2]


  1. ^ a b Short bio at the medical center of the Giessen-Marburg University, where a dermatology clinic is named after Siemens
  2. ^ a b Hermann Werner Siemens, Who Named It
  3. ^ Wheelwright, Jeff, Discover magazine, Study the Clones First, August 2, 2004
  4. ^ Joseph, Jay, The Gene Illusion, Page 18-21, Published by Algora Publishing, 2004, ISBN 0-87586-344-2