Oryx & Crake by Margaret Atwood

Pigs might not fly, but they are strangely altered. So, for that matter, are wolves and raccoons. A man, once named Jimmy, now calls himself Snowman and lives in a tree, wrapped in an old bed sheet. The voice of Oryx, the woman he loved, teasingly haunts him. The green-eyed children of Crake are his responsibility.