Manlaff and Toewoman were greatly startled the day they first emerged from their cave in 1974 and discovered they had landed in the Future.
The Stone Age couple are still trying in this updated 2020 reissue to decide whether a wheel should be called a wheel, or whether to call it a brick; and what happens when you decide to plant your grandmother.
New tales have replaced some of the originals. Others have disappeared.
The 1974 edition became an LP, was rewritten as a play and staged in the Edinburgh Fringe Festival, and in Balliol College, Oxford University and elsewhere.