Background
Clausen was born in Eskilstrup on the island of Falster, Denmark. He was the son of Christen Augustinus Clausen (1858-1938) and Christine (Christensen) Clausen (1856-1933).
Clausen was born in Eskilstrup on the island of Falster, Denmark. He was the son of Christen Augustinus Clausen (1858-1938) and Christine (Christensen) Clausen (1856-1933).
He studied Mendel"s genetics and Darwinian evolutionary theory. In 1913 he entered the University of Copenhagen, where he studied botany, genetics and ecology. Christen Raunkiær suggested he undertake graduate studies and Clausen chose to study the genetics and ecology of the plant family Violaceae.
He studied hybridization patterns across a range of environments and described introgression of genes between species.
He completed his masters degree in 1920 and was appointed assistant professor to geneticist Øjvind Winge at the Royal Veterinary and Agricultural University in Copenhagen. In 1926, Clausen was awarded his Doctor of Philosophy for his work on Violaceae.
His monograph was one of the first publications that combined systematics, ecology and genetics for any plant group.
He is considered a pioneer in the field of ecological and evolutionary genetics of plants. During 1927-1928, Clausen received a Rockefeller scholarship to study at the University of California, Berkeley where he worked on the genetics of the genus Crepis with East. B. Babcock. During this time he met Californian botanist Harvey Monroe Hall, who invited Clausen to return to the United States to work on the ecological genetics of Californian native species.
Clausen returned to the California in 1931 as a staff member at the Carnegie Institution of Washington Department of Plant Biology at Stanford, California.
He would become a naturalized citizen of the United States during 1943. With taxonomist David Doctorate. Keck and physiologist William Hiesey, he formed the first interdisciplinary effort to combine genetics, ecology and systematics in order to understand the ecological genetics of the evolutionary process in California plants.
The project lasted 20 years during which they performed some of the classic experiments in plant ecology in which they looked at species formation across Altitudinal zonation using experimental plots at Stanford (near sea level), at Mather in Sacramento County (at about 4,600 feet), and at Timberline in the Sierra Nevada (at about 10,000 feet).
National Academy of Sciences. Royal Swedish Academy of Sciences]
Clausen was a member of the First Baptist Church of Palo Alto, California.