Left, photograph of an ebony wood ‘Tree of Life’ carving, made by a craftsman of the Makonde tribe in Tanzania, about 1970 (provided by Nicholas Humphrey; see pages 745–754). Top right, a social group of captive rooks, including a bonded pair (48 and 49). These pairs resemble the alliances of primates (photograph, Christopher Bird and Nathan Emery; see pages 489–505). Bottom right, chimpanzees communally ‘ant-dipping’ using long wands at a nest hole, in Gombe, Tanzania. Social complexity here ranges from multi-party competition to opportunties for social learning of a challenging foraging skill (photograph, D. Bygott and A. Whiten; see pages 603–620).