Well, Buddhism goes further. We not only share the animal world, but other "realms" as well. Hindu/Buddhist cosmology sees the world as a wheel of 6 realms. Many texts will say that this concept can be experienced within. Any being can experience any one of these worlds. Those "realms" are seen as different degrees of counsciouness. As humans, we can feel more connected to one of those states. But many of us will experience the pride of the gods realm, the jealousy of the titans, the desire of the human state, the ignorance of the animal realm, the hunger of the hungry ghosts and the rage of hells... even in the very same day.

Of course, as I did not read the book, I am not sure what the author means exacly. Boundaries are on our mind. We create them. But the difference between humans and animals seems to me a difference of degree of counsciouness.