# Did she really live 122 years?

Even more famous than “the Japanese dude who won the hot dog eating contest” is “the French lady who lived to be 122 years old.”

But did she really?

Paul Campos writes:

Here’s a statistical series, laying out various points along the 100 longest known durations of a particular event, of which there are billions of known examples. The series begins with the 100th longest known case:

100th: 114 years 93 days

90th: 114 years 125 days

80th: 114 years 182 days

70th: 114 years 208 days

60th: 114 years 246 days

50th: 114 years 290 days

40th: 115 years 19 days

30th: 115 years 158 days

20th: 115 years 319 days

10th: 116 years 347 days

9th: 117 years 27 days

8th: 117 years 81 days

7th: 117 years 137 days

6th: 117 years 181 days

5th: 117 years 230 days

4th: 117 years 248 days

3rd: 117 years 260 days

Based on this series, what would you expect the second-longest and the longest known durations of the event to be?

These are the maximum verified — or as we’ll see “verified” — life spans achieved by human beings, at least since it began to be possible to measure this with some loosely acceptable level of scientific accuracy . . .

Given the mortality rates observed between ages 114 and 117 in the series above, it would be somewhat surprising if anybody had actually reached the age of 118. Thus it’s very surprising to learn that #2 on the list, an American woman named Sarah Knauss, lived to be 119 years and 97 days. That seems like an extreme statistical outlier, and it makes me wonder if Knauss’s age at death was recorded correctly (I know nothing about how her age was verified).

But the facts regarding the #1 person on the list — a French woman named Jeanne Calment who was definitely born in February of 1875, and was determined to have died in August of 1997 by what was supposedly all sorts of unimpeachable documentary evidence, after reaching the astounding age of 122 years, 164 days — are more than surprising. . . .

A Russian mathematician named Nikolay Zak has just looked into the matter, and concluded that, despite the purportedly overwhelming evidence that made it certain beyond a reasonable doubt that Calment reached such a remarkable age, it’s actually quite likely, per his argument, that Jeanne Calment died in the 1930s, and the woman who for more than 20 years researchers all around the world considered to be the oldest person whose age had been “conclusively” documented was actually her daughter, Yvonne. . . .

I followed the link and read Zak’s article, and . . . I have no idea.

The big picture is that, after age 110, the probability of dying is about 50% per year. For reasons we’ve discussed earlier, I don’t think we should take this constant hazard rate too seriously. But if we go with that, and we start with 100 people reaching a recorded age of 114, we’d expect about 50 to reach 115, 25 to reach 116, 12 to reach 117, 6 to reach 118, 3 to reach 119, etc. . . . so 122 is not at all out of the question. So I don’t really buy Campos’s statistical argument, which all seems to turn on there being a lot of people who reached 117 but not 118, which in turn is just a series of random chances that can just happen.

Although I have nothing to add to the specific question of Jeanne or Yvonne Calment, I do have some general thoughts on this story:

– It’s stunning to me how these paradigm shifts come up, where something that everybody believes is true, is questioned. I’ve been vaguely following discussions about the maximum human lifespan (as in the link just above), and the example of Calment comes up all the time, and I’d never heard anyone suggest her story might be fake. According to Zak, there had been some questioning, but it it didn’t go far enough for me to have heard about it.

Every once in awhile we hear about these exciting re-thinkings of the world. Sometimes it seems that turn out to be right (for example, that story about the asteroid collision that indirectly killed the dinosaurs. Or, since we’re on the topic, the story that modern birds are dinosaurs’ descendants). Other times these new ideas seem to have been dead ends (for example, claim that certain discrepancies in sex ratios could be explained by hepatitis). As Joseph Delaney discusses in the context of the latter example, sometimes an explanation can be too convincing, in some way. The challenge is to value paradigm-busting ideas without falling in love with them.

– The Calment example is a great illustration of Bayesian inference. Bayesian reasoning should lead us to be skeptical of Calment’s claimed age. Indeed, as Zak notes, Bayesian reasoning should lead us to be skeptical of any claim on the tail of any distribution. Those 116-year-olds and 117-year-olds on Campos’s list above: we should be skeptical of each of them too. It’s just simple probabilistic reasoning: there’s some baseline probability that anyone’s claimed age will be fake, and if the distribution of fake ages has wider tails than the distribution of real ages, then an extreme claimed age is some evidence of an error. The flip side is that there must be some extreme ages out there that we haven’t heard about.

– The above discussion also leads to a sort of moral hazard of Bayesian inference: If we question the extreme reported ages without correspondingly researching other ages, we’ll be shrinking our distribution. As Phil and I discuss in our paper, All maps of parameters are misleading, there’s no easy solution to this problem, but we at least should recognize it.

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