Evolutionary dead-end

[necturus]

Last weekend my father gave me a book that once belonged to his great-grandfather. It's signed by my father and grandfather, with the notations "this book belonged to my father" and "and mine". I have it now, but there are none to come after me, so I haven't bothered to sign it.

Oh, and the title of the book? The Origin of Species, by Charles Darwin, M.A., LL.D, F.R.S.