This blog is intended to go along with Population: An Introduction to Concepts and Issues, by John R. Weeks, published by Cengage Learning. The latest edition is the 12th (it came out in 2015), but this blog is meant to complement any edition of the book by showing the way in which demographic issues are regularly in the news.

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Thursday, October 6, 2016

Could Humans Live Past 122 Years?

Every species on earth has a life span--an oldest age to which one of its members is known to have lived. Notice that I worded that carefully. We are talking about a verified oldest age of one member of the species (whether a human, a dog, a whale, or a redwood tree). The current record holder among humans is a French woman, Jeanne Clement, who died in 1997 at the age of 122 years, as I note in Chapter 5 of my text. I bring this up because a two-page letter published this week in Nature has received a surprising amount of publicity and even pushback, leading to a discussion about it yesterday in Nature and also in yesterday's NYTimes. Here's the deal:
An analysis of global demographic data published in Nature suggests that humans have a fixed shelf life, and that the odds of someone beating Calment’s record are low — although some scientists question this interpretation. They say that the data used in the analysis are not unequivocal, and that the paper doesn’t account for future advances in medicine.
The data in question come from the Human Mortality Database originally developed at UC Berkeley by John Wilmoth, who is now Director of the Population Division of the UN. That project was undertaken in collaboration with the Max Planck Institute for Demographic Research in Germany, where the data are now housed. Jan Vijg, a geneticist at Albert Einstein College of Medicine in New York City and two of his graduate students, "reasoned that if there’s no upper limit on lifespan, then the biggest increase in survival should be experienced by ever-older age groups as the years pass and medicine improves. Instead, they found that the age with the greatest improvement in survival got steadily higher since the early twentieth century, but then started to plateau at about 99 in 1980. (The age has since increased by a very small amount)."

The data suggest that the odds are pretty slim of living past 115 (you can get a quick shot of similar data at this website of record holders). Jeanne Clement is clearly an outlier, but at the same time she redefined upward what the human life span really is. Could someone live longer? My view is yes, but the chances are clearly slim. That seemed to be Vijg's reasoning also, and if you've read my book, you know that I agree with his view that we should spend our time and resources increasing human health span (the number of healthy years we live) rather than on thinking that we can somehow increase the maximum age to which a single human could live.

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