Children of Bob
Another from 2008. My take on the concept of the most recent common ancestor (MRCA), and specifically on "Y-Chromosome Adam," the counterpart to "Mitochondrial Eve."
Beautiful Earth
An original from 2008. The title/line in the chorus was inspired by Bugs Bunny commenting on the lunar view in 1948's "Haredevil Hare."
The Prisoner
Filk of "The Boxer" by Simon & Garfunkel. "I am not a number, but my story's often told..."