Yorick is a "him." He's a Neanderthal recruited for time travel, and at some point he says to Rod (the main character) that he doesn't actually have the same reasoning ability as H. sapiens, so his speech isn't actually conscious speech so much as it is a vast collection of subroutines (much like the sound bite carts radio stations (used to) use). When Rod comments that "programming" all of this would be a vast undertaking, Yorick just taps his head and makes some comment about how a brain is an amazing thing.Don't know it.
--Patrick