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A carved wooden idol that David purchased in a New York auction room is traced back to its origin: Easter Island. It was cheap because the seller probably believed it was a forgery. But during the course of this programme its whole history is discovered: carved on Easter Island while there was still wood of the toromiro tree (now extinct on the island), to represent the god Makemake, traded with the crew of captain Cook's ship, transported to Tahiti, probably traded by the Tahitians with the crew of an American whaling ship and ended up in the US.

This time the birds are in Australia and New Guinea. Like the Birds of Paradise, Bowerbird females build their nests and raise their young alone so the male has all day to gather his treasures and create his bower. There seems to be a bowerbird rule: the more elaborate the bower the plainer the bird - the simpler the bower, the more vivid the plumage. David mischievously moves a leaf or a piece of lichen to see what the bird will do, then moves away. The bird flies back scoldingly and fussily returns his artistic display to its former perfection. Fascinating.

This natural history of music begins with David playing the piano (rather well, to my untrained ear). Searching for the origins of human music, he traces its connections to the musical sounds that other animals make: the beauty of the wolf's howl, the complexity of the bat's cry, the deep rumble of the elephant's signals, the acoustically sophisticated sounds the dolphin produces and the songs of whales and birds. Why do these animals produce this amazing variety of sounds? It's all tied up with sex and territory.