December 21, 1889: American Geneticist Sewall Wright was Born
Sewall Green Wright (December 21, 1889 – March 3, 1988), American geneticist, was one of the pioneering scientists in population genetics. Wright developed the mathematical basis for modern evolutionary theory, and established Shifting Balance Theory.
Reference
https://global.britannica.com/biography/Sewall-Wright
http://www.nature.com/scitable/topicpage/sewall-wright-and-the-development-of-shifting-30508
Image Source
http://www.genetics.org/content/202/1/3