On the Tendency of Species to form Varieties; and on the Perpetuation of Varieties and Species by Natural Means of Selection Letter" from Darwin to Asa Gray. This was the first announcement of the Darwin – Wallace theory of evolution by natural selection; the papers appeared in print on 20 August 1858. The presentation of the papers spurred Darwin to write a condensed "abstract" of his "big book" on "Natural Selection". This was published in November 1859 as "On the Origin of Species". On the voyage of the "Beagle" the young Charles Darwin took a break between graduating and starting his career as a clergyman to study the natural history of South America, an interest he had developed at the University
Genetics and the Origin of Species of Species" in 1859." Dobzhansky was plagued by a form of leukemia in his later years, but he remained vigorously active until the day before his death on December 18, 1975. During his lifetime he was the recipient of many honors and awards. For "Genetics and the Origin of Species" Dobzhansky was awarded the Daniel Giraud Elliot Medal from the National Academy of Sciences in 1941. Sixty years after its publication, the National Academy of Sciences commissioned a book entitled "Genetics and the Origin of Species: From Darwin to Molecular Biology 60 Years After Dobzhansky". It was also included in