Hominids

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 ou...