differences than does tool using. Sixth, heretofore unknown sex differences in behavioral patterns may emerge as more detailed observations are made. For example, through video-recording, we have noticed that immature females tend to play more in trees than do their male counterparts, and when females play on the ground, they tend to perform more somersaults than do males. Seventh, this book also may contribute to the further testing of the gestural origin hypothesis of human language origins. Gestures appear to be integral to spoken language, because they accompany the speech of people who are blind from birth. Observations of spontaneous behavior in captivity show that chimpanzees and bonobos use brachio-manual gestures more flexibly across contexts than they do facial expressions and vocalizations. Gestures seem less closely tied to