So not the classic from Anton Chekhov, this one was about a tribe of prehistoric hominids where Uncle Vanya was a member of the tribe that insisted that they were evolving too slowly.
He was the one that tried to eat everything, because how else would you know which one killed you.
I brought the paperback many years ago, at least 25, mainly because the cover had Terry Pratchett's name on the cover (in a rather larger font than the actual authors name). It was accidently disposed of and would love to read it again so any help would be appreciated.
The Fifth Elephant, a 1999 novel by Terry Pratchett, includes a pastiche of Chekhov plays in which "the gloomy and purposeless trousers of Uncle Vanya" are loaned to Captain Vimes.