It is a great honor to be asked to introduce this exciting new volume, having been heavily involved in the first comprehensive synthesis in the early 1980s. Gibbons are the most enthralling of primates. On the one hand, they are the most appealing animals, with their upright posture and body shape, facial markings, dramatic arm-swinging locomotion and suspensory postures, and devastating duets; on the other hand, the small apes are the most diverse, hence biologically valuable and informative, of our closest relatives. It is hard for me to believe that it is 40 years to the month since I...