Anagenesis, also known as "phyletic change," is the evolution of species involving an entire population rather than a branching event, as in cladogenesis. When enough mutations have occurred and become stable in a population so that it is significantly differentiated from an ancestral population, a new species name may be assigned. A key point is that the entire population is different from the ancestral population such that the ancestral population can be considered extinct. A series of such species is collectively known as an evolutionary lineage.

It is easy to see from the preceding definition how controversy can arise among taxonomists when the differences are significant enough to warrant a new species classification. Anagenesis may also be referred to as "gradual evolution".

The philosopher of science Marc Ereshefsky argues that paraphyletic taxa are the result of anagensis. The lineage leading to birds has diverged significantly from lizards and crocodiles, allowing evolutionary taxonomists to classify birds separately from lizards and crocodiles, which are grouped as reptiles.

Dan Barton (September 20, 1921 – December 13, 2009) was an American actor.

Dan Barton was born as Daniel George Berman in Chicago, Illinois. At the age of 16, he began his lifelong acting career starting out in radio. He served in the Army in World War II acting with Alex Nicol and Mickey Rooney. While stationed in Paris he edited a humor magazine. After returning to the States he was cast as Stefanowski in the stage play Mr. Roberts where he met actor Cliff Robertson who became his lifelong friend.

While on tour Dan met his first wife, actress Anne Barton. They married between a matinee and evening performance. The best man at their wedding was actor John Forsythe. Anne, who died in 2000, was best known as Eddie Haskell’s mother in “Leave it to Beaver.” They had two children, musician Steve Barton from the band Translator and Susan Berman. In 2005, Dan married Gyl Roland, daughter of Gilbert Roland and Constance Bennett.

In the late 1940s, Dan Barton appeared on stage in the successful stage production “Mr. Roberts” alongside Cliff Robertson, Lee Van Cleef, John Forsythe and Brian Keith.