 Biodemographic studies have found that even genetically identical laboratory animals kept in constant environment have very different lengths of life, suggesting a crucial role of chance and early-life developmental noise in longevity determination.This leads to new approaches in understanding causes of exceptional human longevity.As for the future of human longevity, biodemographic studies found that evolution of human lifespan had two very distinct stages – the initial stage of mortality decline at younger ages is now replaced by a new trend of preferential improvement of the oldest-old survival.