A brief clip of a Siamang (Symphalangus syndactylus) vocalizing.

Some mornings in the forests of Indonesia, a male and female gibbon will perform a musical duet. The pair will call out, staking their claim in the forest, often answered by neighboring pairs, their treetop display the result of much practice so that the pair can get things “just right.” In order to achieve an effective display the two gibbons need to form a pair bond, but the strength and permanence of the pair-bond between these apes has long been obscured by the sociological biases of the scientists studying them. Indeed, the ideas of what a “nuclear family” should be and what monogamy means in nature have been heavily influenced