The history of beards in the Western Christian world is complicated. Up to the end of the 12th century, beards were very common as a sign of holiness. Facial hair and very long hair can both be a sign of rejection of the world of fashion and temporal power. Irish (and some other) beards were forked. St Humphrey (Onufrios) lived 40 years in the desert “clad only in his own hair” - mostly taken to be his long beard as well as body-hair.
But after the 12th century, with pogroms against the Jews, and the rise of towns and cities in Western Europe, beards went out of fashion, because they were associated with Jews and Muslims, Turkish and otherwise.
However, in the early 1520s, for complicated Italian political reasons, beards came into fashion again - this was during the reigns of Henry VIII of England and Francois I of France. They remained in fashion until the beginning of the 18th century, when wigs came in. Wigs and beards don’t go together.
Then beards came into fashion again (but not with Popes and other high clerics) in about the 1840s (Prince Albert) and they lasted until the First World War, when lice were perceived as a major problem for soldiers.
From then until the late 1960s beards were worn by artists and bohemians, and of course some tramps and bums.
Excellent books have been written on the subject by sociologists and anthropologists. Moustaches have a separate (though sometimes linked) history…
Fine beards (on popes, painters and other celebrities) can be seen on http://hairymouthfuls.tumblr.com - a blog dedicated to beards as art.