Recent work on collective animal behaviour shows that relatively simple behaviours by each animal acting individually can together produce complex, emergent behaviours larger than the parts. This self-organization occurs despite the limited cognitive abilities of individual animals and despite each animal’s limited access to global information, or the ‘big picture’. ‘The wisdom of crowds’ explains this phenomenon termed swarm intelligence by considering the murmurations of starlings, schools of fish, ant trails, and termite nest-building. The behaviour of individual animals and the rules of interaction, from which the collective behaviours emerge, have evolved under natural selection just like other behaviours. The application of such self-organization models is also discussed.