This point and the few exceptions to it are addressed in the footnotes. I was skeptical too, particularly of the claim that the lisp family tree is rooted in Fortran, but the claims seem to be pretty well researched.

Maybe, but there are plenty of languages I would say are completely independent -- APL, Prolog, and Forth don't seem to resemble Fortran in any major way. At least Lisp shares the same notion of functions=subroutines.