Every empire needs a succession plan. Making babies - and raising them - is crucial for every species to survive. In some social circles, it takes a village to raise a family. In others, a single parent is all that stands between the vulnerability of youth and the threats of the wild. The Barbary macaques of the Rock of Gibraltar are the only free-living primates in Europe. They conquered the rock some 600 years ago. Part of the secret to their success is "alloparenting." Fathers play a large role in rearing young, but they don't just look after their own young. They help look after all the troop's young.

pt. 1. Family: Macaques -- pt. 2. Family: Flamingos -- pt. 3. Family: Manatees.