The maximum life span of a group is a measure of the maximum number of years a single member of that group has survived, or is a reflection of the current age of the oldest living member, if that is higher. For example, the oldest recognized person on record was a French woman named Jeanne Calment, who lived for 122 years and 164 days.

Maximum life span differs from the more commonly quoted mean life span, which is the average lifespan or the life expectancy of the group. The mean span varies with a species' susceptibility to disease, accidents, suicides, and homicides, whereas maximum life span is determined by the simple "rate of aging."

Maximum life span for humans has remained around 115-120 calendar years throughout recorded history, despite the often primitive medical treatments used for hundreds of years. Reduction of infant mortality has accounted for most of the increased longevity, but, since the 1960s, mortality rates among those over 80 years have decreased by about 1.5% per year.

Advances in medicine and health care and the recent discovery that calorie restriction, along with adequate nutrition, can slow the aging process, can account for much of the constancy in the results.

Maximum life span is usually longer for species that are larger, can fly, and have larger brains. For example, when we look at other primates (such as the chimpanzee and the gorilla), of the approximately 20,000 to 25,000 genes in the human genome, it is estimated that only 2% of these are different from the chimps', but that 2% decreases the average lifespan to only 52 years. The difference in longevity between humans and chimps could be due to as few as a hundred genes or less; however, there may be other factors that shorten the life span of chimpanzees, especially those in the wild. Scientists are studying the differences to determine what, exactly, changes between the two to create the differences in lifespan expectancy.