Flight of the Mariner(1997)
A novel by Paul Ware
Shushuan, the ancient, forgotten birthplace of humankind, still calls to its long-lost offspring. But only a handful of those descendants are able to respond. When David and Kate are transported to Shushuan, they find themselves in a barbaric world where their lives are constantly in peril.
Used availability for Paul Ware's Flight of the Mariner