In this polished anthropological SF yarn, the first of a trilogy from Nebula Award winner Sawyer (The Terminal Experiment), Neanderthals have developed a radically different civilization on a parallel Earth, as both sides discover when a Neanderthal physicist, Ponter Boddit, accidentally passes from his universe into a Canadian underground research facility. Fortunately, a team of human scientists, including expert paleoanthropologist Mary Vaughan, promptly identifies and warmly receives Ponter. Solving the language problem and much else is a mini-computer called a Companion implanted in the brain of every Neanderthal. A computerized guardian spirit, however, doesn't eliminate cross-cultural confusion permanent male-female sexuality, rape and overpopulation are all alien to Ponter nor can it help his housemate and fellow scientist back in his world, Adikor Huld, when the authorities charge Adikor with his murder. Ponter's daughter Jasmel believes in Adikor's innocence, but to prevent a horrendous miscarriage of justice (Adikor could be sterilized), she must try to reopen the portal and bring her father home. The author's usual high intelligence and occasionally daunting erudition are on prominent display, particularly in the depiction of Neanderthal society.

-Publisher's Weekly 

First volume of the author's acclaimed "Neanderthal Parallax" trilogy about an alternate Earth where Neanderthals survived to the present day and we did not.