If I may add to this: chimps have even been known to lie. One of two chimps broke something during the absence of a human caretaker. Upon returning, the caretaker - using sign language - asked the chimps who did it, and the guilty one pointed at the other one. It was not just thinking, but thinking ahead.
We are all atheists about most of the gods that humanity has ever believed in. Some of us just go one god further. - Richard Dawkins