Hominids (Neanderthal Parallax)

From back cover Tor paperback February 2003:

*Hominids* examines two unique species of people. *We* are one of those species; the other is the Neanderthals of a parallel world where *they* became the dominant intelligence. The Neanderthal civilization has reached heights of culture and science comparable to our own, but with radically different history, society and philosophy.

Ponter Boddit, a Neanderthal physicist, accidentally pierces the barrier between worlds and is transferred to our universe. Almost immediately recognized as a Neanderthal, but only much later as a scientist, he is quarantined and studied, alone and bewildered, a stranger in a strange land. But Ponter is also befriended -- by a doctor and a physicist who share his questing intelligence, and especially by Canadian geneticist Mary Vaughan, a woman with whom he develops a special rapport.

Ponter's partner, Adikor Huld, finds himself with a messy lab, a missing body, suspicious people all around and an explosive murder trial. How can he possibly prove his innocence when he has no idea what actually happened to Ponter?