Multi-faceted design: Why peacock feathers were sickening to Darwin
The aspects of design evidenced in feathers resist attempts at an evolutionary explanantion. Darwin confided in a letter to American botanist Asa Gray, “The sight of a feather in a peacock’s tail, whenever I gaze at it, makes me sick!” (Darwin 1860). Each peacock feather has an eye at a certain position along the shaft of the feather. From one feather to another the eye is at a different distance along the stem. However, together the feathers form a pattern of eyes regularly spaced throughout the fan. The eye is formed by minute abrupt changes in the thickness of keratin on each barb, producing bronze then blue then bronze. The blue sections are of differing lengths on each barb, but combine to form an elliptical ring. Wildlife writer Philip Snow comments, “such feathers are actually colourless themselves, relying upon...tiny ‘crystals’ to split white light into its constituent rainbow hues,” (Snow 2006: 96). Each feather is precisely rooted to be aligned in position when the peacock displays. The genetic information governs root position, stem length and barb colouring to conform to a geometric pattern. Burgess estimates that “20 genes are required for the peacock tail,” (Burgess 2001).
Burgess identifies the peacock tail as an example of “Irreducible complexity,” the phenomenon observed when something manufactured or natural is so complex it will not function unless all the parts are in place simultaneously. A mouse trap or burglar alarm can exemplify this: if the spring or any other part of the mouse trap is missing it will not work. If the pressure mat or any component of the alarm is not present the system is non-operational. Likewise, unless feathers have all the components (shaft, barbs and barbules) they cannot function. For peacocks there is another level of irreducible complexity, “in the beautiful patterns,” (Burgess 2001). The cell has the information for the components, but the ordering of the components in relation to one another does not come from any one cell, but is an over-arching design.
How Darwin came to terms with the problem: sexual selection
To account for the evolution of what appeared to be gratuitous beauty, eleven years later Darwin published his theory of “sexual selection.” The basis of this theory was that the peahen selected the male with the most attractive display of tail feathers. In this story there were lots (millions?) of different varieties of peacock, but the pea hens preferred the ones with the most symmetrical and aesthetically pleasing tail feathers, these survived and the genes for the most beautiful feathers were passed on so beauty increased. This seemed to provide some kind of rejoinder to the argument that the feathers demonstrated design, and with subsequent studies that seemed to back it up sexual selection became, “part of the canon of evolutionary biology,”(Morell 2008).
The problem with this theory
However detailed research led by Mariko Takahashi of the University of Tokyo has thrown a spanner in the works for the theory that peahens select mates according to the beauty of their tail feathers. The study found there was no relationship between tail quality and mating. The researchers measured tail quality by the length of the feathers and the number of eyes on the feathers, and monitored whether females chose mates with the best quality tails. The researchers were surprised to find, having logged 268 matings over seven years, peahens mated with as many “poor quality” males as with “high quality” males. They concluded, “the male’s feather train failed to impress or excite, much less interest, the females,” (Catchpoole 2008).
Looking for fig leaves
The pattern formed on the peacock’s tail is the combined effect of about 100 feathers as they fan out. There is an over-arching design. It could be compared to a piece of architecture with doors and windows and stairs and plumbing. The bricks and the window panes and the steps and the pipes are all individually made, but they are made to be incorporated into a greater scheme. It is not a chance occurrence, just as the windows, doors and pipes have not come together naturally to form the building. The edifice wouldn’t even have the right components unless it has all been set up on purpose.
Likewise, the peacock’s tail feathers demonstrate an over-arching design that cannot be accounted for by slight successive changes over time. There is evidence that the components of the display have been intentionally organised to produce an overall effect. That effect arises as the components are combined. Slight, successive mutations would not be able to work towards a final result as they are purely random and have no goal in view. Besides this, there is great technological intricacy in the production of the feathers themselves from the bird’s DNA, an infinitely complex code which then is implemented by an infinitely sophisticated construction process that includes growth and maintenance as well as order and visual effect. This information is highly structured and complex and involves an idea of what the overall appearance of the tail will look like. It is information that works to a specification over and above the instructions for any one component.
The theory of “sexual selection” was in the first place something of a fig leaf to cover the nauseating embarrassment felt by Darwin at the evidence of design posed by feathers and peacock feathers in particular. As Catchpoole notes, “even if the females were impressed, this does not explain the origin of the genes that code for the elaborate tail feathers,” (Catchpoole 2008, see also Burgess 2001).
Alexander, D. (2008, 2014) Creation or Evolution: Do We Have to Choose? Oxford: Lion Hudson
Burgess, S. (2001) “The Beauty of the Peacock Tail and the Problems with the Theory of Sexual Selection,” Answers in Genesis, August 1, 2001, https://answersingenesis.org/natural-selection/peacock-tail-beauty-and-problems-theory-of-sexual-selection/.
Catchpoole, D. (2008) Peacock Tail Tale Failure: Charles Darwin’s ‘theory of sexual selection’ fails to explain the very thing Darwin concocted it for Creation Ministries International https://creation.com/peacock-tail-tale-failure
Darwin, C. (1859) The Origin of Species, London: Murray
Darwin, F., (Ed), (1860) Letter to Asa Gray, dated 3 April 1860, The Life and Letters of Charles Darwin, D. Appleton and Company, New York and London, Vol. 2, pp. 90–91, 1911
Morell, V., Peacock feathers: That’s So Last Year, ScienceNOW Daily News, 2 April 2008.
Snow, P. (2006) The Design and Origin of Birds Leominster: Day One
Takahashi, M. and others, Peahens do not prefer peacocks with more elaborate trains, Animal Behaviour 75(4):1209–1219, 2008 | doi:10.1016/j.anbehav.2007.10.004
Viegas, J., Female peacocks not impressed by male feathers, Discovery News, 28 March 2008