This is really interesting.

I've been turning this idea over in my head every now then as a mental exercise (bus ride material). One, it validates my reasoning that rigid single-inheritance trees are a bad representation.

What my mind kept turning to was the possibility of Neanderthals and early humans interbreeding yet being different species that had a common ancestor. It isn't really a tree in that case.

Two, this comment gives my past time more food for thought!