I alleged not long ago that my father's hairstyle has, since he crossed the threshold into adulthood, not changed.
In the interest of completeness, he sent me a photo refuting this claim (he is at the center of the back row).
Based on the fact that I recognize a few of the friends in the photo as his compatriots from graduate school (perhaps the preponderance of thick framed glasses should tip you off to that fact...they were all in the sciences as far as I am aware), I assume that this photo was taken sometime in the mid-1960s. Before the 60s became the 60s. Before Berkeley became Berkeley.
So the addition of the beard occurred sometime thereafter. Following a particularly bad sunburn that my dad sustained on a trip to Death Valley with my mother, I'm told. And thus began an era.