Darwin’s Sexy Sons

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by GregLaden on September 2, 2011 · 0 comments

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Darwin saw the same thing others had seen … an enigma of nature … and took equal note of it. But others explained this enigma in a way that made sense to them but that was completely wrong. Darwin produced an alternative explanation that was both convincing and frightening. Darwin’s explanation was much closer to the truth than what others had said, yet it was still wrong enough that what we teach in school today is not at all the same thing.

I’m talking, of course, about exaggerated male traits especially in birds.

Nevertheless I know of no fact in natural history more wonderful than that the female Argus pheasant should appreciate the exquisite shading of the ball-and-socket ornaments and the elegant patterns on the wing-feathers of the male. He who thinks that the male was created as he now exists must admit that the great plumes, which prevent the wings from being used for flight, and which are displayed during courtship and at no other time in a manner quite peculiar to this one species, were given to him as an ornament. If so, he must likewise admit that the female was created and endowed with the capacity of appreciating such ornaments. I differ only in the conviction that the male Argus pheasant acquired his beauty gradually, through the preference of the females during many generations for the more highly ornamented males; the æsthetic capacity of the females having been advanced through exercise or habit, just as our own taste is gradually improved. In the male through the fortunate chance of a few feathers being left unchanged, we can distinctly trace how simple spots with a little fulvous shading on one side may have been developed by small steps into the wonderful ball-and-socket ornaments; and it is probable that they were actually thus developed.

Everyone who admits the principle of evolution, and yet feels great difficulty in admitting that female mammals, birds, reptiles, and fish, could have acquired the high taste implied by the beauty of the males, and which generally coincides with our own standard, should reflect that the nerve-cells of the brain in the highest as well as in the lowest members of the Vertebrate series, are derived from those of the common progenitor of this great Kingdom. For we can thus see how it has come to pass that certain mental faculties, in various and widely distinct groups of animals, have been developed in nearly the same manner and to nearly the same degree.

In this series of blog posts, I’m mainly trying to let Darwin speak for himself, but on this topic (in this post and the next) I’ll expand a bit more on what he was saying and what we think now. Notice that Darwin is speaking of an aesthetic sense found in female birds, and a corresponding expression of that aesthetic in males. Others of that day recognized that male pheasants were absurdly done up to the extent that it made them vulnerable to predation and other hazards, and that females were rather turned on by this birdy beauty. And, they assumed that god had created these animals this way for some reason which may or may not be fathomable. What Darwin reasons was quite different: He saw the aesthetic as more or less a given (though subject to refinement by selection) and he reasoned that the female sense of aesthetic … that thing that linked together the visual appreciation of a male peacock (or whatever) and the females sex drive (though Darwin was rarely so forward in his language) was the driving force in male evolution. Selection for the beauty that made the females more likely to be a mate drove male evolution.

This is correct, and it is what we think today, but there is a flaw in the theory as Darwin conceived of it. The sensible female is the problem. Female aesthetics could drive male beauty to absurd levels, which is fine up to a point because males are rather useless most of the time and cause more trouble than they are worth. Indeed, I personally think that a legitimate driving force in sexual selection could be the degree to which females get most males to die young. It’s a great strategy. But at some point the females should be selected, if they are indeed under selection, to prefer males that will pass genes on to their own sons that are not utterly absurd.

There is an obvious answer to that objection to Darwin’s Theory, but I’ll leave that for next time.

Darwin, C. R. 1882. The descent of man, and selection in relation to sex. London: John Murray. 2nd edition, fifteenth thousand.

The drawing is Paradisea Papuana (T. W. Wood), from The Descent of Man

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