Trading years for tears, and loving it

Trading years for tears, and loving it

Photo by Visual Stories || Micheile on Unsplash

Originally published 18 January 1999

You’ll be the death of me yet.”

What par­ent has­n’t said that to a child. Or at least thought it.

You’re tak­ing years off my life,” we say. And maybe we mean it and maybe we don’t, but it seems like all that ener­gy we are invest­ing in our off­spring must come from somewhere.

Now, a cou­ple of Euro­pean geron­tol­o­gists think they have demon­strat­ed that hav­ing kids real­ly does take years off our lives.

Rudi Wes­t­en­dorp, of Lei­den Uni­ver­si­ty Med­ical Cen­ter in the Nether­lands, and Thomas Kirk­wood, of the Uni­ver­si­ty of Man­ches­ter in Britain, stud­ied 12 cen­turies of genealog­i­cal records of British aris­toc­ra­cy, more than 30,000 indi­vid­u­als all together.

What they found, they wrote in the jour­nal Nature, seems to be a trade-off between child­bear­ing and longevity.

Women in their sam­ple who lived to ripe old ages (beyond age 80) tend­ed to have few­er off­spring than the broad­er pool of women who sur­vived beyond menopause but did not live so long.

Men showed a sim­i­lar con­nec­tion between hav­ing prog­e­ny and decreased lifespan.

The longest-lived indi­vid­u­als, male and female, were the least fecund.

What does this mean?

It might mean a lot of things.

Maybe longevi­ty and decreased fer­til­i­ty are genet­i­cal­ly related.

Maybe the body has only so much phys­i­cal cap­i­tal: We can invest our resources in mak­ing chil­dren, or in keep­ing the body in tip-top repair — but not both.

Maybe kids real­ly do dri­ve us to an ear­ly grave.

Or maybe British aris­to­crats are just so eccen­tric, ser­vant-rid­den, or inbred that noth­ing we observe in the pat­tern of their lives applies to the rest of us.

Nev­er­the­less, many folks in our health-obsessed soci­ety will be eye­ing these results with curios­i­ty, bal­anc­ing the asset of a big fam­i­ly against the prospects of play­ing ten­nis at age 85.

Wes­t­en­dorp and Kirk­wood believe their study of British aris­to­crats argues for a genet­ic link between fer­til­i­ty and decreased longevi­ty. By mass­ing their data in var­i­ous ways, they show that socioe­co­nom­ic diver­si­ty and oth­er envi­ron­men­tal fac­tors are unlike­ly caus­es of the observed trend.

Pre­vi­ous research with fruit flies has con­vinc­ing­ly demon­strat­ed a genet­ic link between ear­ly breed­ing and decreased longevi­ty. Flies selec­tive­ly bred for long life­times have few­er off­spring, and flies select­ed for late fer­til­i­ty live longer with enhanced resis­tance to stress.

The rea­sons for all of this are not entire­ly clear.

Genes that cause the body to wear out in old age will not be strong­ly sup­pressed by nat­ur­al selec­tion; life-short­en­ing genes that kick in late in life will already have been passed along to the next gen­er­a­tion before they decrease fitness.

Late-act­ing dele­te­ri­ous genes may even be favored if they have ben­e­fi­cial effects ear­ly in life, as geron­tol­o­gist Daniel Promis­low points out in his Nature com­men­tary on the study of British aristocrats.

Twen­ty-two years ago, Kirk­wood adopt­ed this trade-off between ear­ly ben­e­fits ver­sus lat­er costs in his “dis­pos­able soma” the­o­ry. (Soma refers to an organ­is­m’s body as dis­tinct from its repro­duc­tive cells.) Accord­ing to the the­o­ry, pro­duc­tion of off­spring diverts the body’s genet­i­cal­ly lim­it­ed resources away from the job of main­tain­ing and repair­ing cells, with aging as the result.

The the­o­ry works well enough with fruit flies. And now Wes­t­en­torp and Kirk­wood think they see the same thing at work in a human population.

Well, maybe.

As Promis­low points out, a few things are clear. Child­less women ben­e­fit from a decreased inci­dence of heart dis­ease and cer­vi­cal can­cer lat­er in life, but they have an increased risk of breast can­cer and res­pi­ra­to­ry disease.

Beyond that, things get very mud­dy, espe­cial­ly the sup­posed genet­ic link between repro­duc­tion and longevi­ty in humans. Wes­t­en­dorp and Kirk­wood have found them­selves a nifty data set, but so many vari­ables lurk with­in it that any con­clu­sions drawn from it have to be high­ly tentative.

I sus­pect par­ents have pret­ty much guessed all along what these geron­tol­o­gists are try­ing to prove.

Every par­ent knows there is some­thing like a “dis­pos­able soma,” and every sleep­less night mind­ing a col­icky baby or wait­ing up for a tardy teen uses up some of it.

We did­n’t need sci­en­tists to tell us that a petu­lant 13-year-old can take years off our lives, or that putting a kid though col­lege can cause more gray hairs than old age.

Bar­bara King­solver’s nov­el The Poi­son­wood Bible is a tale that pret­ty well describes the wear and tear of fam­i­ly life. At one point, the Mama in the sto­ry laments a lost child. “The sub­stance of grief is not imag­i­nary. It’s as real as rope or the absence or air, and like both those things it can kill,” she says.

Bear­ing chil­dren opens our hearts to whole new dimen­sions of grief and stress, and both can take a somat­ic toll.

But so what? Even if hav­ing kids leads us to an ear­ly grave, most of us would still choose to do it.

Kids may lit­er­al­ly be the death of us, but they are also the best part of our lives.

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