Why is all this sex necessary anyway?

Why is all this sex necessary anyway?

Photo by Anna Shvets from Pexels

Originally published 13 February 1995

What’s the sto­ry of love?”

I posed the ques­tion to Dr. Hen­ry Testos­terone, not­ed evo­lu­tion­ary biologist.

Valen­tine’s Day is com­ing up,” I said. “Read­ers will be inter­est­ed to know why sex evolved.”

Ah, an inter­est­ing ques­tion,” he replied, “and hot­ly debat­ed among my colleagues.”

His response took me by surprise.

I had thought the ques­tion was set­tled long ago,” I said. “When I was in school, all the biol­o­gy books said sex evolved to pro­duce genet­ic vari­a­tion — a shuf­fle of the genes with each gen­er­a­tion. Accord­ing to Dar­win­ian the­o­ry, vari­a­tion helps a species adapt to a chang­ing environment.”

True enough,” said Testos­terone. “The genet­ic vari­a­tion the­o­ry held the court for a hun­dred years. But recent­ly biol­o­gists have dis­cov­ered that asex­u­al­ly-repro­duc­ing species can adapt just as quick­ly to a chang­ing environment.”

Huh…?”

For exam­ple, dan­de­lions repro­duce with­out sex, and look how suc­cess­ful­ly they com­pete with sex­u­al­ly-repro­duc­ing plants.”

Then why…?”

There are lots of the­o­ries,” said Testos­terone. “Per­haps sex evolved as a way of repair­ing DNA dam­age. Per­haps as a way of help­ing organ­isms keep ahead of the chang­ing strat­a­gems of pathogens and par­a­sites. Or maybe sex is a bio­log­i­cal quirk that became embed­ded in the genes with our bac­te­r­i­al ances­tors and has been around ever since. And so on.”

Sure­ly one the­o­ry holds sway?”

The one thing all biol­o­gists agree upon is that sex is exceed­ing­ly costly.”

Cost­ly?” I was think­ing of the 60 bucks I had just shelled out for long-stemmed roses.

The time and ener­gy spent find­ing and court­ing a part­ner are exceed­ing­ly great for most sex­u­al species — time and ener­gy that could be bet­ter spent seek­ing food and evad­ing predators.”

I began remem­ber­ing song lyrics of my youth: “The price of love, the price of love, the debts you pay with tears and pain…”

Exact­ly. It is far more effi­cient to repro­duce by cloning, bud­ding, or partheno­gen­e­sis — vir­gin birth — none of which requires a part­ner. Lots of asex­u­al species do quite well, thank you.”

It makes me hurt so bad to see you again…”

Pity the poor pea­cock that must car­ry around a mass of gaudy feath­ers — attrac­tive to pea­hens, per­haps, but con­spic­u­ous to preda­tors. Or the ram that must grow bur­den­some horns so that he can butt heads with his rivals.”

…like nee­dles and pins.”

Sex is also a ter­ri­bly effec­tive way of spread­ing pathogens and par­a­sites. Sex­u­al­ly trans­mit­ted diseases.”

For every lit­tle kiss there’s a lit­tle teardrop, for every sin­gle thrill there’s anoth­er heartache…”

And males. Males are the most waste­ful thing of all. They pro­vide genes but lit­tle else. A quick tum­ble in the sack, then they are off to the fridge for a beer or to turn on the TV to watch foot­ball. In most species, females get stuck with the nit­ty grit­ty of rais­ing the young.”

…Yes, love is a hurtin’ thing.”

There’s a sea anemone that lives along the Pacif­ic coast of the Unit­ed States and Cana­da that comes in two vari­eties, sex­u­al and asex­u­al. The asex­u­al anemones repro­duce by divid­ing down the mid­dle — cloning, if you will. They seem to do as well, per­haps bet­ter, than the sex­u­al anemones. The clones all live hap­pi­ly togeth­er with­out com­pe­ti­tion or the both­er of sex.”

I remem­bered read­ing some­where that a typ­i­cal male thinks about sex every 20 sec­onds. Or is it 20 min­utes? In any case, we waste a lot of time and ener­gy. I was begin­ning to under­stand what Testos­terone meant by the costs of sex.

He con­tin­ued: “Since sex is so cost­ly, Dar­win­ian the­o­ry requires that it must con­fer some great ben­e­fit upon sex­u­al­ly-repro­duc­ing organ­isms. It’s sur­pris­ing, real­ly, that it is so hard for biol­o­gists to fig­ure what the ben­e­fit is.”

I mused, “When a man loves a woman, can’t keep his mind on noth­ing else…”

…he’d trade the world for the good thing he’s found,” added Testos­terone, with unchar­ac­ter­is­tic romance. Per­haps he was tak­en by the charm of the season.

Only love can break a heart…”

Only love can mend it again.”

Yeah,” I said, revert­ing to sci­en­tif­ic objec­tiv­i­ty. “But how does that fit in with Dar­win­ian theory?”

Don’t know,” replied Testos­terone. “That’s the sto­ry of…”

That’s the glo­ry of…”

Love.”

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