Darwin's Theory of Evolution and Irreducible Complexity

Introduction to Irreducible Complexity

The construct of irreducible complexity is a pivotal aspect of both genetic theory and Darwinian theory. It represents a nexus between the older science of biology from which Darwin built his theory and modern genetic engineering. Darwin's own phrase for irreducible complexity — most commonly associated with his argument about the construction of the eye — was "Organs of extreme perfection and complication." Darwin further explained:

"Reason tells me, that if numerous gradations from a simple and imperfect eye to one complex and perfect can be shown to exist, each grade being useful to its possessor, as is certainly the case; if further, the eye ever varies and the variations be inherited, as is likewise certainly the case and if such variations should be useful to any animal under changing conditions of life, then the difficulty of believing that a perfect and complex eye could be formed by natural selection, though insuperable by our imagination, should not be considered as subversive of the theory" (Darwin 1859).

Examples of irreducible complexity on the biological organ level include the heart, the eye, and the ear — though they were not recognized as irreducible structures in Darwin's lifetime — and there are, in fact, "tens of thousands of irreducibly complex systems on the cellular level" (Abbey, et al. 2011). Perhaps in the construct of irreducible complexity a foundation for intelligent design may be found; however, that line of reasoning is beyond the scope of this essay. The construct of irreducible complexity may be seen as a foundation of Darwin's theory of evolution, as Darwin observed that "complex forms evolve from non-complex forms over time… based on natural selection, which acts to accumulate and transform minor advantageous genetic mutations" (Abbey, et al. 2005).

It is important to link these two disciplines, since to argue for or against evidence of Darwin's theory without framing it in scientific progress is akin to claiming that Don Quixote cannot be the first modern novel because it is, after all, simply a written record of the ballads in the tradition of the picaresque novel. Don Quixote was the novel of its time — indeed the only anti-romantic novel of the time — in quite the same way that the theory of evolution was the explanation for inherited biological difference as it related to environmental survival.

The Peppered Moth: Natural Selection in Action

One of the simplest examples of Darwin's theory of evolution can be accessed by referring to the study of peppered moths in English industrial cities. Peppered moths as a species present a variety of wing and body coloration patterns, which have apparently changed — evolved — over time (Majerus 2004). In nineteenth-century England, people heated homes, factories, and common spaces with coal-burning furnaces, without any type of filter to reduce environmental pollution (Majerus 2004). As a result of this heavy pollution, the lichen that grew on trees under normal conditions was killed, and where the tree bark had once been light in color, it became darkened by deposits of coal soot (Majerus 2004). Indeed, the exteriors of buildings were also turned dark by coal soot deposits.

Unfortunately for some of the peppered moths, light-colored wings stood out rather starkly on dark-colored surfaces, which served to attract hungry, savvy birds to easy meals (Majerus 2004). The birds did not as readily pick off moths that were naturally located on the darker end of the wing and body color spectrum (Majerus 2004). As would be expected, more dark-colored peppered moths survived in higher numbers and — genetic heritability being what we know it is today — passed on their dominant dark color to offspring in greater numbers (Majerus 2004).

Critics of the peppered moth studies enjoy emphasizing that it is the frequency of the appearance of one or the other colored moth that was altered in concordance with the altered environment — darker tree bark and buildings brought about changes in predation, which resulted in a preponderance of darker moths. Yet it is entirely possible, in the long term, for the peppered moth to revert entirely to the light-winged and -bodied variety as pollution has abated and environments have been cleaned up. What if all the dark moths developed a melanic-based disease and completely died off during a time when dark moths otherwise had higher survival rates? The important consideration in this example is that variation within a species is a survival advantage, such that species naturally tend toward variation. Indeed, a cleaner English countryside is already seeing a resurgence of the lighter-colored moths.

Darwin, Mendel, and the Foundations of Genetics

We may attribute our understanding of these genetic mechanisms to Gregor Mendel, who is associated with the discovery and articulation of the fundamental laws of trait heritability through his work on pea plants. Criticisms of Mendel's work are relatively rare, in that Mendel did not associate or disassociate his discoveries with a higher being, and drew no direct lines between pea plants, monkeys, and human beings. Liu (2005) examined the chronology of historical findings in the fields of biology and genetics to better determine the direction of influence for both Darwin and Mendel. The influence that Darwin had on Mendel through The Origin can be seen in the transmission of the term gene, which was derived from pangen, a word coined by Darwin from Pangenesis (Lin 2005). Lin (2005) further clarifies the historical relationship between the two scientists:

"Darwin was the first to clearly describe almost all genetical phenomena of fundamental importance, and was the first to present a developmental theory of heredity — Pangenesis — which not only greatly influenced many subsequent theories of inheritance, particularly those of de Vries, Galton, Brooks and Weismann, but also tied all aspects of variation, heredity, and development together, provided a mechanism for most of the observable facts, and is supported by increasing evidence" (1).

Conclusion: Creationism and the Limits of Evolutionary Objection

Darwin understood the constraints that common sense and conventional wisdom place on science, citing the ancient adage vox populi, vox dei — the voice of the people is the voice of God — as something that "cannot be trusted in science" (Darwin 1859). Yet, in a later edition of The Origin, Darwin attempts to frame his argument not in scientific terms but in the lexicon of common sense:

"It is scarcely possible to avoid comparing the eye to a telescope. We know that this instrument has been perfected by the long-continued efforts of the highest human intellects; and we naturally infer that the eye has been formed by a somewhat analogous process. But may not this inference be presumptuous? Have we any right to assume that the Creator works by intellectual powers like those of man?… In living bodies, variation will cause the slight alterations, generation will multiply them almost infinitely, and natural selection will pick out with unerring skill each improvement… may we not believe that a living optical instrument might thus be formed as superior to one of glass, as the works of the Creator are to those of man?"

At risk of stating the obvious, objections to the theory of evolution are most solidly grounded in a belief in creationism, wherein everything that exists now exists precisely as it did at the moment of creation — and less solidly grounded in an appreciation of change as an essential attribute and a critical essence of biological organisms.

Works Cited

Abalaka, M.E. & Abbey, F.K. (2011). Charles Darwin theory of evolution and modern genetic engineering. Journal of Pharmaceutical Research and Opinion, 1(7): 174–177.

Bergman, G. Pangenesis as a source of new genetic information: the history of a now disproven theory. Rivista di Biologia, 99(3): 425–443. 2006, September–December.

Darwin, Charles. "Difficulties on theory." Chapter 6. On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life. 1st edition. 1859.

Liu, Y. Darwin and Mendel: who was the pioneer of genetics? Rivista di Biologia, 98(2): 305–322. 2005.

Lui, Y. A new perspective on Darwin's Pangenesis. Biological Reviews of the Cambridge Philosophical Society, 83(2): 141–149. 2008.

Majerus, M. The peppered moth: decline of a Darwinian disciple. Lecture to the British Humanist Association, 12 February 2004.

Richmond, M.L. The 1909 Darwin celebration: reexamining evolution in the light of Mendel, mutation, and meiosis. Isis, 97(3): 447–484. 2006.