Today I’m 50

Today is my 50th birthday.  I’m very glad to be part of a species that lives so long, and it appears that I should thank other lusty old men, and especially the fertile young women who find them attractive.  The details:

Evolutionary theory predicts that senescence, a decline in survival rates with age, is the consequence of stronger selection on alleles that affect fertility or mortality earlier rather than later in life. Hamilton quantified this argument by showing that a rare mutation reducing survival is opposed by a selective force that declines with age over reproductive life. He used a female-only demographic model, predicting that female menopause at age ca. 50 yrs should be followed by a sharp increase in mortality, a ‘‘wall of death.’’ Human lives obviously do not display such a wall. Explanations of the evolution of lifespan beyond the age of female menopause have proven difficult to describe as explicit genetic models.

Here we argue that the inclusion of males and mating patterns extends Hamilton’s theory and predicts the pattern of human senescence. We analyze a general two-sex model to show that selection favors survival for as long as men reproduce. Male fertility can only result from matings with fertile females, and we present a range of data showing that males much older than 50 yrs have substantial realized fertility through matings with younger females, a pattern that was likely typical among early humans. Thus old-age male fertility provides a selective force against autosomal deleterious mutations at ages far past female menopause with no sharp upper age limit, eliminating the wall of death.

So from old men everywhere to young women everywhere: Thank you thank you!

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  • Michelle

    Happy Birthday!

  • Willem

    Happy birthday! You’re double my age and still entertaining (me)! And since you’ve asked for it:

    From young men to young women everywhere: Thank you thank you too!

  • gwern

    Hm. If young women getting with old men selects against things that kill old men (and thus women), then should we blame young men not getting with old women as much as we give credit to the young women? :)

    • Heather315

      It would seem logical that younger men (with younger, healthier sperm) would be more likely to take advantage of possible later-life fertility in older women. So, to Cougars everywhere–get on with it and increase our lifespan already!!!

  • http://www.intrade.com John Delaney

    Robin,

    A big Happy Birthday to You.

    I will raise a glass to your health and happiness tonight in Dublin.

    At around 5PM ET if you care to raise your own glass you will not be alone.

    Warm regards,

    John

  • Mike

    Seems like old women should thank old men and young women too.

  • Marshall

    I’ll just thank you, Robin for a good blog, I look forward to every day.

  • Vladimir Nesov

    Happy birthday, Robin!

    Today I’m exactly half your age.

  • Robert Koslover

    From Saturday Night Live, Oct. 15, 1977, hosted by Hugh Hefner,

    Summary: Hugh Hefner sings “Thank Heaven for Little Girls”, as a scroll reveals the true intent of his performance.

    That’s what you meant, isn’t it?
    Happy birthday, Robin.

    • http://hanson.gmu.edu Robin Hanson

      No comment. :)

  • http://ajayjetti.com Ajay Jetti

    Happy birthday Robin

    I hope you live longer than life allows you to.

    And yes, thanks to all the older women too….

  • Sean C.

    Happy Birthday.

    I’ve also seen studies (genealogical analysis of family trees in rural Quebec) that show that a grandmother can greatly increase the fertility of her children by contributing to the family well being.

    Like a non-fertile worker bee, just because she’s done bearing children doesn’t mean she’s no longer contributing to the survival of her genes.

  • http://doesitfollow.blogspot.com/ przemek

    Happy Birthday.

  • http://www.ephorie.de vJD

    Happy birthday and keep up the good work!

    cheers,
    vJD

  • Matt

    Happy Birthday Robin! When I run for president in 30 years, my motto for saving health care costs will be summed up in one Matthew McConaghey quote, “I keep getting older, they stay the same age.”

  • Carl Shulman

    Happy Birthday Robin!

    We should also thank relatively low levels of predation on humans in the ancestral environment.

  • Thanatos Savehn

    Happy Birthday. I beat you to the milestone by a few months and have been an avid reader of this site for a long time.

    Add my story to the pile of anecdotes. My wife’s considerably younger and she’s at home with the newest baby while I’m at the office (it’s ok to surf the web when you’re the boss) winning the bread. So far, so good.

    I wonder though about the direction of causality. Having a young wife and kids keeps you younger; keeps you busy; keeps you getting up in the morning and hunting the woolly mammoths. Maybe that keeps you fertile longer. Or maybe I’m saying the same thing. Dunno.

    • Jo Puschek

      …….. or maybe it just makes you look older ……

  • http://michaelgr.com/ Michael G.R.

    At the risk of being redundant, happy birthday!

  • Ned

    Robin, happy birthday!

    As far as causes of human longevity: young women actually look for (older) men with resources, not only fertile men. That explains their abhorrence towards very old men, those that ‘may die at any moment’ – traditionally, women had no way to keep the material resources after the partner’s death.

    What I think offers better explanation is the role grandmothers play in raising their grandchildren. (This is not my original idea, but I cannot remember where I read about this, so no link.) In essence, if grandmothers contribute significantly to survival of their own grandkids, that would promote lifespan to the point where their daughters hit menopause. Rapid decline in female fertility after the age of 35 gives lifespan (absent violent death and death from contagious deceases) of about 70 years.

    • http://www.nancybuttons.com Nancy Lebovitz

      I’ve heard that it’s maternal grandmothers which contribute to the survival of their grandchildren, not grandmothers in general.

  • http://yudkowsky.net/ Eliezer Yudkowsky

    May the cities in your wake
    Burn like candles on your cake
    It’s your birthday
    (thud)
    Happy birthday
    (thud)

  • fenn

    Sounds like Viagra might do more for life extension than frozen heads

  • michael vassar

    Happy Birthday to Robin and my condolences to all those who died too young to become his ancestors.

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  • http://hertzlinger.blogspot.com Joseph Hertzlinger

    50? Isn’t that 10 Celsius?

  • jonathan

    Happy birthday!

    I only had time to scan the paper but it doesn’t seem like they looked at how senescence – as they generally mean, past female fertility – may be a function of average life spans, meaning that selection to produce sufficient reproductive capabilities connect to average life spans and that may generate non-selected correlations or, in other words, longer potential life span.

  • John Maxwell IV

    While you’ve been alive, the planet you’re on has orbited its sun a number of times equal to the product of the number of fingers you have on one hand and the number of fingers you have on both hands.

    Congratulations.

  • Andrew Mundy

    Happy Birthday Robin. Here’s to 500 more!

  • http://cob.jmu.edu/rosserjb Barkley Rosser

    Happy birthday.

    Just to keep things in perspective, you have the same birthday as my mother, who just turned 96. May you live so long as well.

  • http://timtyler.org/ Tim Tyler

    Article talks about the “wall of death” as though younger women and older men are the only factor diminishing its impact. That’s not really right – selection for infant dependency and parental care also makes parents of both sexes live longer.

    Since women typically live longer than men, a theory of longevity that only applies directly to extending male lifespan seems to have a somewhat questionable status. The case of women strongly indicates that there’s something else going on. One should establish what that is – and then see if that is sufficient to explain the extended lifespan of males too.

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