The word longevity is sometimes used as a synonym for life expectancy in demography or to connote long life, especially when it concerns someone or something lasting longer than expected (an ancient tree, for example).Reflections on longevity have usually gone beyond acknowledging the brevity of human life and have included thinking about methods to extend life. Longevity has been a topic not only for the scientific community but also for writers of travel, science fiction, and utopian novels.