Bass Players Named John

I'm not sure why this should be, but it seems to me that Bass Players of what I regard as the golden age of Rock and Roll--1965-1975 are disproportionately named John

John McVie  played with John Mayall's Blues Breakers and is the "Mac" part of the name of Fleetwood Mac, in both it's Peter Green and Buckingham/Nicks incarnations
John Entwistle played with The Who
Jack (John William) Cassady played with the Jefferson Airplane and Hot Tuna.
John Paul Jones (John Baldwin) - Led Zeppelin and many other groups
Jack (John Symon Asher) Bruce - Cream and many other groups.
Jaco (John Francis Anthony) Pastorius - Blood Sweat and Tears, Weather Report, Joni Mitchell
John Lodge - Moody Blues
John Kahn - Jerry Garcia Band
John Deacon - Queen

The reality is that this is not really anomalous--John was the third most common name in the early 40s when most of these guys were born, and it remained that popular until the 1970s.  The surfeit of Johns probably led to the decline in the popularity of the name.