Evolutionary basis for Spitzer's adultery?

Pulitzer Prize-winning science writer Natalie Angier has a piece today in the NY Times about the rarity of monogamy in animal species:

... Sexual promiscuity is rampant throughout nature, and true faithfulness a fond fantasy.

Oh, there are plenty of animals in which males and females team up to raise young, as we do, that form “pair bonds” of impressive endurance and apparent mutual affection, spending hours reaffirming their partnership by snuggling together like prairie voles or singing hooty, doo-wop love songs like gibbons, or dancing goofily like blue-footed boobies.

Yet as biologists have discovered through the application of DNA paternity tests to the offspring of these bonded pairs, social monogamy is very rarely accompanied by sexual, or genetic, monogamy. Assay the kids in a given brood, whether of birds, voles, lesser apes, foxes or any other pair-bonding species, and anywhere from 10 to 70 percent will prove to have been sired by somebody other than the resident male.

(Extra paragraphing added.)

Evolutionary psychologists and social biologists tend to think that this furtive, uneasy coexistence of monogamy and promiscuity arises from a confluence of genetic- and social factors:

• All of us are descendants of ancestors who, by definition, did at least the minimum necessary to pass on copies of their genes to another generation.
• Statistically, a father who cheats on his mate is likely to pass on more copies of his genes than one who doesn't cheat (because he's more likely to have a greater number of offspring).
• Other things being equal, a mother who tries to enforce fidelity in her mate is more likely to have help, economic and otherwise, in raising her offspring; this ups the odds that her offspring will survive to reproductive age and pass on copies of her genes (and their fathers') to grandchildren.
• On average, mothers who cheat are likely to diversify the genetic risk portfolio of their offspring, because of the increased odds that their offspring will be fathered by several different males of varying genetic profiles.
• When parents stay together to help with the raising of their grandchildren, it enhances even further the odds of that parents' genes will survive into future generations.

In short, from a purely-pragmatic perspective, both monogamy and promiscuity have their evolutionary advantages.

I suspect this is another example of the watermelon-seed effect, in which opposing forces — in this case, the desire for both sexual freedom and a faithful mate — can unexpectedly result in progress (cf. the Hegelian dialectic).

Comments

[Redlefty]

Fine, but did you wife fall for it when you told her that some promiscuity is a rational behavior with species-related advantages? :)

Ha!

[D. C. Toedt]

She reminded me that years ago I taught her to shoot .... :-)