Maximum Individual Life Span

Limits to average life span, or life expectancy at birth, are one issue. When people discuss limits to the human life span, however, they often have another idea in mind: the upper limit to an individual life span. Instead of asking how long we can live on average, we might ask how long one lucky individual can hope to live. This concept is actually much easier to understand than the notion of an upper limit to life expectancy.

Who is the oldest person who has ever lived? Even if we can never have a definitive answer to this question, we can at least imagine the existence of such a person. Maybe he or she (probably she) is still alive today. Or, maybe she lived hundreds of years ago but vanished without leaving a trace—no birth certificate, no census record, and not even a newspaper article about her incredible feat of longevity.

Who is the oldest person alive today? That person might or might not be the oldest person ever. However, identifying the world's oldest person is very difficult even today, because of the widespread practice of what demographers politely call "age misstatement" (36). Putting it less politely, some people lie about their age. Others, if asked, give the wrong age because they do not remember, because they are not numerate, or because they simply never paid attention to such matters. Such age misstatement often occurs in the absence of written records to prove or disprove the reported age.

Should we believe people who claim to be extremely old without proper documentation? Certainly, we should believe them, since there is no point in calling anyone a liar or questioning their memory. In terms of a scientific discussion about longevity, however, experts agree that it is best to ignore undocumented cases of extreme longevity. Thus, when we make statements about who is the oldest person alive today or in the past, we limit ourselves to cases where solid evidence exists (37).

To be accepted as a valid instance of extreme longevity, thorough documentation is required—not just a birth certificate but also a series of documents and a life history that is consistent with the written records. Ideally, if the person is still alive and mentally able, an oral history is obtained and checked against all available evidence—making sure, for example, that this person is not the son or daughter of the person in question.

Indeed, there are numerous examples of supposed extreme longevity that turned out to be cases of mistaken identity (37). Perhaps the most notorious example was a French Canadian named Pierre Joubert, who was supposed to have died at the age of 113 years in 1814. This case was listed for many years by the Guinness Book of World Records (38). When genealogical records were examined closely, however, two men named Pierre Joubert were identified—a father and his son. It was the son who died in 1814, 113 years after the birth of the father (39). Such mistakes are not uncommon, and whether they are the result of deliberate misrepresentation or honest error is irrelevant. In either case, a complete investigation should be required before accepting such reports as factual.

The historical record is still held by a Frenchwoman, Jeanne Calment, who died at age 122 in August of 1997 (40). Madame Calment lived in Arles, a town with very complete civil records (births, deaths, marriages, baptisms, etc.) going back several centuries. Fortunately, since these records were not destroyed in any war, it was possible to trace the life of Jeanne Calment very closely. It was also possible to reconstruct her family genealogy and to document that a disproportionate number of her ancestors were long lived as well. Of course, it is only one example, but the case of Jeanne Calment suggests that extreme longevity may have at least some hereditary component (41).

The oldest man whose age was thoroughly verified was Christian Mortensen, who died in 1998 at the age of 115 (42,43). A Japanese man named Shigechiyo Izumi was reportedly 120 years old when he died in 1986. Recent editions of Guinness World Records still maintain that Izumi is the oldest man on record. However, this case has now been rejected by almost all experts who are familiar with it, including the Japanese man who originally brought it to the attention of Guinness (44-46), and the common belief is that Izumi was in fact "only" 105 years old at the time of his death.

It is reasonable to ask what we have learned in general from these few cases of exceptionally long-lived individuals. Admittedly, the cases of Calment and Mortensen tell us nothing about the trend in maximum longevity. Maybe these are just two cases that we have had the good fortune of documenting in recent years. Maybe there were other individuals who were just as old as Calment or Mortensen who lived years ago, and we missed them. These are valid points, so we must turn to other evidence if we want to know about trends in extreme longevity.

In order to study historical trends in extreme longevity, we need a well-defined population with reliable records over a long period of time. For that purpose, we turn to a small subset of countries that have kept reliable population statistics for many years. The longest series of such data comes from Sweden. These records are thought to be extremely reliable since 1861, even in terms of the age reporting of individuals at very old ages (44). Vital records have a very old history in Sweden, where Lutheran priests were required to start collecting such information at the parish level in 1686. Such records were eventually brought together into a national system in 1749. In 1858, the present-day National Central Bureau of Statistics was formed, which led to further improvements in data quality. Furthermore, by the 1860s, the national system of population statistics was already more than 100 years old, so it was possible to check claims of extreme longevity against birth records from a century before. These historical developments account for the unique quality of the Swedish mortality data.

Figure 5 shows the trend in the maximum age at death for men and women in Sweden during 1861 to 2005. The trend is clearly upward over this time period, and it accelerates after about 1969. The rise in this trend is estimated to be 0.44 years (of age) per decade prior to 1969, and 1.1 years per decade after that

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