When we see animals doing remarkable things, how do we know if we're simply seeing tricks or signs of real intelligence? Are talented animals just obeying commands, or do they have some kind of deeper understanding? One of the biggest challenges for animal researchers is to come up with tests that can distinguish between the two.

Imagine a life-form whose brainpower is to ours as ours is to a chimpanzee’s. To such a species, our highest mental achievements would be trivial. Their toddlers, instead of learning their ABCs on Sesame Street, would learn multivariable calculus on Boolean Boulevard. Our most complex theorems, our deepest philosophies, the cherished works of our most creative artists, would be projects their schoolkids bring home for Mom and Dad to display on the refrigerator door.

I try to keep this in mind when tied in to a rope 75 feet up in a tree... The history of ideas about our place in the universe has been a long series of let-downs for those who like to believe we are special.

I'm optimistic. I see no longer people accepting fuzzy thinking in the world. The change is not that people aren't still saying under-informed things. The change is that if you're in power and you say something under-informed, there are people out there with a voice who will take you to task for having done so

We are part of this universe; we are in this universe, but perhaps more important than both of those facts, is that the universe is in us.

Three and a half million years ago our ancestors - yours and mine - left these traces [indicates footprints]. We stood up and parted ways from them. Once we were standing on two feet, our eyes were no longer fixated on the ground. Now, we were free to look up and wonder.

When your reasons for believing something are justified ad hoc, you are left susceptible to further discoveries undermining the rationale for that belief.