If you read my post on the Philosophy of Mind, you know this is a topic that intrigues me: How do people think? How is it different from other mammals? How did that process result in us, the alpha animal, despite our lack of claws, canines and thick skin?
One oft-discussed factor that divides human from non-human is consciousness–we are aware of ourselves and other species aren’t (although that pillar is crumbling as has every other seminal difference). Read Scientific American’s discussion of this:
Is complexity the secret to sentience, to a panpsychic view of consciousness?
Do you think that your newest acquisition, a Roomba robotic vacuum cleaner that traces out its unpredictable paths on your living room floor, is conscious? What about that bee that hovers above your marmalade-covered breakfast toast? Or the newborn who finally fell asleep after being suckled? Nobody except a dyed-in-the-wool nerd would think of the first as being sentient; adherents of Jainism, India’s oldest religion, believe that bees—and indeed all living creatures, small and large—are aware; whereas most everyone would accord the magical gift of consciousness to the baby.
The truth is that we really do not know which of these organisms is or is not conscious.