Days Of Our Lives

Oedipus famously answered this riddle:

What goes on four feet in the morning, two feet at noon, and three feet in the evening?

The answer: people crawl when babies, walk as adults, and use a cane when old. It seems natural to divide lives into three parts: young, middle, and old. But where exactly should the boundaries fall? One tempting approach comes from the facts that in the US today lifespans average about 29000 days, and people typically marry and have kids at about 10000 days. So maybe we should split life into the first, second, and third 10000 days.

If we split life into 5000 days units, we get:

  • 0 days; 0 years – Birth
  • 5000 days; 13.7 years – Mid-puberty
  • 10000 days; 27.4 years – First marriage & kids
  • 15000 days; 41.1 years – Start to notice body decline
  • 20000 days; 54.8 years – Near kids’ first marriage & kids, own peak of relative income, productivity, 90% still alive
  • 25000 days; 68.5 years – Near when most retire, 75% still alive
  • 30000 days; 82.1 years – Typical death age, 42% still alive
  • 35000 days; 95.8 years – Only 4% still alive

Note that 5000 days is near the doubling time of the world economy.

In my life, I married at 10250, had my first kid at 11500, started grad school again at 12400, started at GMU at 14600, and was tenured at 16540. And today I am 20,000 days old, within a few days of all my kids being employed college graduates. So a lot happened to me in that third 5000 days, and I now enter the last third of a typical lifespan, with expected declining (but hardly zero) relative productivity. Of course if cryonics works I might live lots longer.

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  • PetjaY

    I would rather split life in doublings of ages, you change much faster when younger. If you start counting age from fertilization it works pretty well even during first days|weeks.

  • ShardPhoenix

    Happy unbirthday?

  • Stephen Diamond

    So, you’re a “Gemini.” Actually seems to fit!

    • RobinHanson

      Actually I’m Virgo.

  • Dan Dzombak
  • Peter David Jones

    The classical world had world had a seven year linear system, which works well for age of reason at 7, the onset of puberty at 14, the end of adolescence at 21, and full maturity at 28, although it gets vague after that. The mid 3Os are supposed to be the most productive period and might represent the prime of life. Unless that’s 42. 49 could be the menopause. 63 was considered a particularly crucial time then (the grand climacteric), maybe because that’s about as long as most people lived.


    Here’s to hoping for some decent aging delaying gentech soon. Humans are nature’s joke, only a third of our life spent in our prime (and being fertile, in the case of our females).

  • Marc Geddes

    It seems natural to base the divisions on the rate of human aging, at least after 18 years when the annual ‘natural’ chance of death doubles approximately every 8 years. There are 9 natural ‘plys’:
    0-18: Youth
    18-26: Young Adult
    26-34: Young Adult
    34-42: Middle age
    42-50: Middle age
    50-58: Middle age
    58-66: Young Senior
    66-74: Young Senior
    74+ : Old
    [Annual chance of death at 18, about 1 in 2 000]

  • consider

    cryonics? The leading experts in longevity say powerful health pills should be available around 2018 to 2022. That’ll put a nice big hole in the actuary tables… – consider

    • RobinHanson

      Some experts may say that, but “the leading experts in longevity” as a group don’t.

      • consider

        The experts who talk to the press do and they often have sharp disagreements with each other.

        David Sinclair (2013) — 5 to 10 years; or 2020

        Leonard Guarente (2010) — 2015 to 2020

        Cynthia Kenyon (2011) — “not too long, I hope…” Other interviews indicate this decade.

        Lynda Partridge (2011) — “I’d be surprised if not within ten years.”

        Ronald DePino (2010) — after reversing aging in mice, he thinks there will be a pill based on his research “eventually”

        William Andrews (2013) “I’ve never been so optimistic and want to give it to my 85 year old parents”

        Matt Kaeberliein/ Kennedy (2009) “”The possibility that such compounds might exist, and might perhaps even be within reach has gained scientific credibility.” (I emailed him, and he thought likely very close to development but that regulation might put off sales for “decades” I pointed out there is always China.
        Who in the longevity field doesn’t think there will be a pill by 2022?

    • Marc Geddes

      ‘Experts’ are after funding and have to claim they can get results in a reasonable timeframe – in fact its a running joke that the next big breakthrough (in any field) is always ‘within the next 15 years’. It never happens of course.
      Lets not kid ourselves: Almost nothing bar super-intelligence could put so much as a dent in the relentless doubling of the rate death every 8 years, all the best health treatments could at most delay the inevitable by a few years and alleviate the symptoms somewhat.
      Even SAI (super-intelligence) would be hard-pressed to halt and reverse the damage in such flawed organisms as humans once they had entered the late stages of their lifespans. Even the computational resources of a SAI would be pushed to the absolute limit to crack such a problem.
      Human experts? No chance.

      • IMASBA

        It is unlikely our natural lifespan is the limit of what is physically possible with bodies such as ours. I really wouldn’t be surprised if gentech can help us stay healthy and physically youthful for decades longer than we do now, not by fixing old bodies but by slowing down ageing itself. But I don’t think we’ll see any clinical breakthroughs before 2020. Perhaps in 2030 something like it will be on the market for the ultra rich and then perhaps by 2050 it will be affordable to an infltion-adjusted average Joe.

      • Marc Geddes

        I agree that lifespans on the order of 1000+ years are probably physically possible with the bodies we have now, but such is the complexity of the problem , you would need a super-intelligence to crack it.

      • IMASBA

        I don’t know about “thousands of years” (can we even store that many memories?), but the genetics should mostly be a problem of computational power, not so much of creativity. You’ll need a lot of processing power and/or time to crack the problem, but probably not a super intelligence (current genetics is hampered by resources, not by a lack of ideas).

      • consider

        You make an excellent point for someone who has no idea what he is talking about.

  • vimspot

    How would you compare each 5,000 day periods in terms of pleasure, flow and fulfillment?