survival value
by Paul Niquette
Copyright ©1996 Resource Books All rights reserved.
survival value 

Usefulness in the struggle for survival.  Said of a quality possessed by an organism.

Survival of the individual is inconsequential, according to the latest in evolutionary thought.  Perpetuation of the genes is paramount.

Look no further than the peacock.  If you saw one for the first time in a painting, you might well presume the thing to be merely a figment of the artist's imagination.  Whatever delights to the eye, the imaginary bird's tail feathers would obviously attract the attention of predators.  In the wild, no bird so heavily laden would even be able to fly.

Ah, but the peacock has his tail feathers because peahens like them.
Sometime long ago, let us suppose, peacocks did not sport ornamental plumage.  When a variation (mutant) appeared which did, the peahens of that time took notice.  More to the point, they gave the colorful fellow favored treatment when it came mating time (see concupiscense).  The rest is -- well, prehistory.

The "perpetuation value," in the case of the peacock's tail feathers, is assured by virtue of being selected by the peahen.  Generation after generation, males with the most spectacular feathers left more descendents which carried the genes needed to make those feathers.  "Sexual selection," it's called.

We can move on to another subject now -- except that...uh, why do the peahens like those feathers?
Let us start out as we did before.  Suppose that all peacocks were once dull.  The first brightly colored peacock showed up, and -- oh my gosh! -- the peahens didn't even notice.  Or if they did, they attached no significance to the dazzling plumage.  More likely, they were repulsed by it.  If the peahen were smart, she would want no part of the ostentatious fool, reasoning that her offspring would be vulnerable as hell to predators.

We know, however, that she fell for the colorful display, which makes a strong case for saying that the ancestral peahens were just plain ditzy.  Sexual selection ran amuck.  Until recently, that conclusion was inescapable.

 Any puzzled parent of a dating daughter knows the scene.
But wait.  Ever see a sick peacock?  Neither have I.  But I read once that he would have dull, scraggly feathers.   Not a pretty sight.  One thing you can say: A peahen, by giving reproductive privileges to a colorful peacock, selects a healthy mate -- however inept he might otherwise be.

Full featheration does not necessarily signal a male free of germs and parasites, mind you, but a male whose immune system gives him resistance.  On the contrary, the ostentatious bird may be anything but "clean cut."  The filthier the better, so long as he can still display his plumage as a certificate of good health.

Apparently, vulnerability of offspring to disease is more important than susceptibility of males to predators, and the peahen "knows" that.  She's no bimbo after all.  It is the peacock's immune system that the peahen selects for her offspring.  More precisely, ancestral peahens that did not exhibit that behavior dropped out along the way, their descendents victims of infirmity.

So, the peacock's tail feathers offer no survival value for the peacock only perpetuation value for his genes.  Which is all that matters anyway.

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