The word "longevity" is sometimes used as a synonym for "life expectancy" in demography. However, this is not the most popular or accepted definition. For the general public as well as writers, the word generally connotes "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.
There are many difficulties in authenticating the longest human lifespan ever by modern verification standards, due to inaccurate or incomplete birth statistics. Fiction, legend, and folklore have proposed or claimed lifespans in the past or future vastly longer than those verified by modern standards, and longevity narratives and unverified longevity claims frequently speak of their existence in the present.