Hominids is the first volume of a new series, The Neanderthal Parallax. A deep mine neutrino experiment is disrupted when a human body suddenly appears in the heavy water sensor array. He's still alive - and he's a neanderthal. Meanwhile in a parallel world, a quantum computing researcher has vanished under mysterious circumstances. It's a world where cro-magnon man became extinct, and neanderthals became the dominant species. And it's a world where the disappeared physicist's partner becomes the main suspect in a murder case...
Sawyer compares and contrasts our word with that of the neanderthals, a quiet, peaceful place, where mammoths still roam the northern lands and passenger pigeons blot out the sky. These are two worlds that have a lot to learn from each other, and Sawyer draws this out through the burgeoning relationship between the transposed neanderthal Ponter Boddit and the human geneticist Mary Vaughan. As they struggle to understand each other, in Ponter's home world, there's a race to understand just what happened to the vanished scientist.
Like nearly all Sawyer novels, Hominids is a slow, philosophical tale that builds to a sudden finale. Ponter's and Mary's conversations illuminate the differences between the two worlds, across the whole range of experiences and ideals - focusing strongly on the role of religion in society. Meanwhile Sawyer mixes some of Penrose's thoughts on the quantum nature of intelligence with various interpretations of quantum theory to show the reasons of the divergence between the neanderthal world line and ours.
All in all, an enjoyable read - and the start of what promises to be an interesting trilogy.