By Barry Peters
Most people react with delight when gazing at a feather from a peacock's tail, even more so when the peacock stunningly puts the whole tail on display.
Darwin, on the other hand, found that view disconcerting. Here's how he described it in a letter to a friend in 1860:
"The sight of a feather in a peacock's tail, whenever I gaze at it, makes me sick!"
Darwin himself never actually explained precisely what troubled him about the peacock's tail. But, as an amateur birdwatcher, several possible explanations spring to my mind.
To begin, let's define the problem. Darwin's Origin of Species had just been published a year earlier. His new theory was rooted in the notion that evolution was driven by natural selection. That process presumed that characteristics which enhanced the survival of any given species were likely to be passed on to subsequent generations. Parents with those characteristics were more likely to live long enough to reproduce. Alternative and less-advantageous traits would tend to be weeded out by an earlier death.
Speedier creatures were more likely to survive than those less swift of foot. Those blessed with natural camouflage tended to survive better than those with eye-catching coloration. Those with more acute eyesight and hearing were more likely to do the dining, rather than being dined upon.
Yet here is the peacock. He struts through life with a neon blue body and a humongous tail. Even when not displayed to impress the local pea hens, the peacock's tail is so large several feet of it drags behind him on the ground. In fact, it is incorrectly thought by many that the peacock's tail is so large that it actually precludes him from taking flight.
But the disadvantage to the peacock of such a large tail is remarkable. He is barely able to become airborne at all. And when he does so, it is only for short distances at very slow speeds. On the other hand, any predator who decides to pursue a peacock has a much easier task of simply chasing him and grabbing his tail to bring him down and taking him home for dinner.
Then there's the whole coloration dilemma. Instead of being camouflaged and fading into his environment, the peacock is cursed with plumage that can only be described as "garish." Bright greens, blues, and yellows abound. His natural predators would have to be nigh on blind to miss spotting him.
As an astute naturalist, Darwin would have also noticed the unique design feature within the coloration of birds. No other phylum of the created order had the same remarkable coloration as do the birds of the air. Not even the breathtaking beauty of tropical fish could compare.
To fully appreciate the startling appearance of birds, one has to understand the structure of the feather. Bear with a short avian anatomy lesson.
A typical feather has a shaft up the middle. It gives the feather some rigidity without it becoming fragile. Off of the shaft run parallel vanes. When those are stroked or preened, they seem to stick together. They can be pulled apart, but then re-adhered. This unique function is due to the fact that on the side of each vane are miniature "barbules" and "hooklets." These flexible hooklets grab onto the barbules on the adjacent vanes when the feather is smoothed out. But if something strikes the feather during flight (like a bug), it can pop apart without causing any damage to the feather. Then, at the next rest stop, the bird can coax the feather back into its original shape by preening it. Kind of like nature's earliest Velcro.
Here's where it gets even more interesting for Darwin. The color pattern of an individual feather is not strictly a matter of a given feather or vane being a distinct color. Looking closely at a peacock's tail feather, for example, reveals that as a single vane grows off of the shaft, it often starts out one color, but then changes to several different colors at specific points in its growth.
But the really mind-boggling part of the puzzle was that the series of colors of a given vane coordinated with the colors on nearby vanes to produce a pattern that transcended the structure of the feather itself. Hence the apparent eye-shaped coloration emerging out of the progressive coloration of hundreds of parallel vanes on a peacock's feather was stunning to Darwin. He understood the inadequacy of his theory to explain such a complex pattern of bright colors, displayed on an easel of side-by-side vanes. Haphazard mutations were totally inadequate for the job.
From a "natural selection" perspective, the male peacock was a disaster, a walking refutation of the principles argued by Darwin's new book. In short, Darwin was agreeing that, if his theory were correct, peacocks would have long since become extinct.
Perhaps that was the genesis of Darwin's gastrointestinal discomfort with the peacock.
Or maybe there was even more to his distress.
In the letter in which Darwin complained about the peacock's feathers, the comment immediately preceding this observation provides some additional insight. It states, "It is curious that I remember well time when the thought of the eye made me cold all over, but I have got over this stage of the complaint, & now small trifling particulars of structure often make me very uncomfortable."
Why did the mere thought of the eye give Darwin the heebie-jeebies?
Because he knew that the eye was far too complex of an organ to be explained by his new theory. As he himself conceded, "If it could be demonstrated that any complex organ existed, which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down."
As Darwin grew to understand and appreciate the stunning complexity of the eye, he knew that its development could not be explained by a series of slight modifications each of which gave the recipient an advantage over the previous generation. Indeed, the supposed missing link stages of any species' development would have been significantly disadvantaged by the existence of an incomplete eye.
So Darwin effectively crossed his fingers and hoped that time might provide some explanation for that which made him so "uncomfortable." Unfortunately, rather than simplifying that which he recognized as complex, time has only brought to light a greater degree of complexity in the eye than Darwin could have ever imagined.
So, perhaps, here is the origin of Darwin's dread of the peacock tail.
Not only was the peacock's tail so eye-catching and bulky as to almost guarantee the extinction of any bird burdened with such an appendage, but that same tail had the audacity to taunt Darwin with what appeared to be dazzling eyes at the tip of each of its dozens of tail feathers. The image of the impossibly complex eye repeatedly and brightly superimposed on the peacock's resplendent tail feathers was simply too much for Darwin to bear.
In the end, Darwin at least was able to see that the survival of the peacock species with its stunning and ocular-patterned plumage was, by itself, a refutation of his new theory. And the passage of 150 years has not lessened the quandary posed by the peacock tail to the believability of his theory.
As we marvel at the unlikely existence of an entire avian kingdom capable of defying gravity with sustained flight, let us not lose sight of the Creator's great imagination in festooning such creatures with arresting, but "unnatural," images. For this grand design reveals not mere randomness, but rather intelligence far beyond anything of which we might conceive, much less emulate.
Barry Peters is an attorney in private practice with offices in Eagle, Idaho, and is one of the legal advisors for both ICHE and CHOIS. His law practice focuses on the areas of wills, trusts, probate, real estate contracts, and business formations.