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32.3 x 24.6 cm ⏐ 12.7 x 9.7 in (300dpi)
LIBRARY OF CONGRESS, RARE BOOK AND SPECIAL COLLECTIONS DIVISION / SCIENCE PHOTO LIBRARY LIBRARY OF CONGRESS, RARE BOOK AND SPECIAL COLLECTIONS DIVISION / SCIENCE PHOTO LIBRARY
Darwin's speciation diagram. Illustration from of 'On the Origin of Species by means of natural selection', published in 1859 by the British naturalist Charles Robert Darwin (1809-1882). Detailing his theory of evolution by natural selection, this is Darwin's most famous work. This diagram was the only illustration in his work. It is a tree diagram used to illustrate speciation (the formation of new species). Starting from the bottom, each horizontal line represents 1000 generations. The letters across the bottom represent different species. Some lineages go extinct. Others diverge as a result of natural selection to the extent that they are eventually classified as a new and distinct species.
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