Benefits, constrainsts and the evolution of the family.

Families form when offspring delay dispersal and remain associated with their parents into adulthood. What are the ultimate causes of such philopatry and prolonged association? Two schools of thought have emerged, providing seemingly opposing answers to this question - the 'benefits of philopatry' and the 'ecological constraints' schools. A recent threshold model for delayed dispersal helps clarify the confused semantics of these arguments and demonstrates the complimentarity of the two approaches. Many of the current advantages of family living may have evolved secondarily, however, suggesting that the initial origin of families occurred under conditions of severe competition for breeding vacancies.