The expectation of the life span of a person, culture, etc. Man's expectation of life is one of the simplest ways of measuring his ability to cope with his surroundings. It can rarely be calculated for an ancient population because too few skeletons are usually found to provide an adequate statistical sample for skeletal analysis. Even then the results may be biased, since infants often failed to qualify for ceremonial burial and so may not be represented. The age distribution of even a few skeletons, however, may give useful results.