Variability in adult social bonding behaviour is known to be influenced by genes, early attachment, and later social opportunities. The relative influence of each, however, is unclear, as is the relative influence of each on hormonal and cognitive mechanisms that mediate social bonding behaviour. Within an ERC-funded project (awarded to Catherine Crockford) I investigate the heritability and early-life priming effects of mechanisms driving social bonding and social behaviour in wild chimpanzees.