Map of life expectancy at birth from Global Education Project.

Tuesday, October 16, 2012

Stayin' Alive

Have I used that title before? Anyhow, I've been remarking lately on the astonishingly unique times in which we live. Here's another contribution to the wonderment from an international group of scholars writing in the Proceedings of the National Academy of Sciences. (Yes, you can read it.)

We just take it for granted, but in the wealthy countries, human life expectancy at birth has increased by about 3 months per year since 1840. This means that until the late 1800s, the human life expectancy everywhere was about the same as that of hunter-gatherers, in other words probably about what it had been since the emergence of anatomically modern humans more than a quarter million years ago. A 30 year old hunter-gatherer has about the same probability of death as a 72 year old Japanese. Life span at birth for a hunter-gatherer is about 31. For Swedes, it was 32 in 1900, and it's 82 today.

We don't know exactly how to explain this -- no doubt it's a combination of everything you can think of -- better nutrition, housing, sanitation, medicine, probably lower rates of violence (at least that's what Stephen Pinker thinks, WWII notwithstanding). But it's absolutely astonishing.

The authors' main point is that our assumptions about senescence -- that genetic patterns that are beneficial at young ages, and particularly in the highest reproductive years, are not necessarily beneficial at older ages, so we just fall apart and die -- can't exactly be true. The reductions in death rates have occurred at all ages, and are actually greater past reproductive age.

Keep in mind, we're talking about Sweden and Japan here -- in the U.S. by the way we haven't done nearly as well, but well enough I suppose. But this has completely revolutionized society, culture, the economy, in ways we scarcely notice. I recently embarked on a new and demanding career at the age of 55, and I have complete confidence that I'll hang in long enough to leave a good legacy of accomplishment. As Tom Lehrer put it, "It is a sobering thought, for example, that when Mozart was my age, he had been dead for two years." But that was no great tragedy in Mozart's day, it was typical.

Will this last? Stay tuned.

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