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Anagenesis

The term anagenesis may have been introduced by Huxley (1957) and Rensch (1947, 1960) independently of one another. The reason for the uncertainty is that Rensch (1960) wrote that Sylvester-Bradley had advised him that in 1875, Hyatt had used the term “anagenesis” but with a different meaning. A review of Hyatt’s work, cited as the reference by Rensch, does not reveal the use of the term. Sylvester-Bradley’s informa­ tion was in the nature of “personal correspon­ dence” (it was not in the reference cited by Rensch), and thus we shall have to leave the precise origin of the use of the term unsettled. In fact, Simpson also can be included as part of the relevant history. Simpson (1949) stated that Rensch (1947) proposed the term anagenesis but noted that Rensch acknowledged the fact that he was unaware of Simpson’s earlier work (1944), in which Simpson had described “phyl­ etic evolution,” a process similar to anagenesis.