The argument is structured as a basic modus tollens: if "creation" contains many defects, then design is not a plausible theory for the origin of our existence. It is most commonly used in a weaker way, however: not with the aim of disproving the existence of God, but rather as a reductio ad absurdum of the well-known argument from design, which argues that living things are too well-designed to have originated by chance, so must have been deliberately created by an intelligent God.
Although the phrase "argument from poor design" has seen little use, this type of argument has been advanced many times using words and phrases such as "poor design", "suboptimal design", "unintelligent design" or "dysteleology/dysteleological". The last of these is a term applied by the nineteenth-century biologist Ernst Haeckel to the implications of organs so rudimentary as to be useless to the life of an organism. Haeckel, in his book The History of Creation, devoted most of a chapter to the argument, ending with the proposition (perhaps with tongue slightly in cheek) of "a theory of the unsuitability of parts in organisms, as a counter-hypothesis to the old popular doctrine of the suitability of parts". The term "incompetent design", a play on "intelligent design", has been coined by Donald Wise of the University of Massachusetts Amherst to describe aspects of nature that are currently flawed in design.
Traditional theological responses generally posit that God's creation was perfect but that humanity's misuse of its free will to rebel against God has resulted in the corruption of good design.
Living things are too well-designed to have originated by chance.
Therefore, life must have been created by an intelligent creator.
This creator is God.
"Poor design" is consistent with the predictions of the scientific theory of evolution by means of natural selection. This predicts that features that were evolved for certain uses, are then reused or co-opted for different uses, or abandoned altogether; and that suboptimal state is due to the inability of the hereditary mechanism to eliminate the particular vestiges of the evolutionary process.
In fitness landscape terms, natural selection will always push "up the hill", but a species cannot normally get from a lower peak to a higher peak without first going through a valley.
Several defects in human anatomy can result in death, especially without modern medical care:
In the human female, a fertilized egg can implant into the fallopian tube, cervix or ovary rather than the uterus causing an ectopic pregnancy. The existence of a cavity between the ovary and the fallopian tube could indicate a flawed design in the female reproductive system. Prior to modern surgery, ectopic pregnancy invariably caused the deaths of both mother and baby. Even in modern times, in almost all cases the pregnancy must be aborted to save the life of the mother.
In the human female, the birth canal passes through the pelvis. The prenatal skull will deform to a surprising extent. However, if the baby's head is significantly larger than the pelvic opening, the baby cannot be born naturally. Prior to the development of modern surgery (caesarean section), such a complication would lead to the death of the mother, the baby, or both. Other birthing complications such as breech birth are worsened by this position of the birth canal.
In the human male, testes develop initially within the abdomen. Later during gestation, they migrate through the abdominal wall into the scrotum. This causes two weak points in the abdominal wall where hernias can later form. Prior to modern surgical techniques, complications from hernias, such as intestinal blockage and gangrene, usually resulted in death.
The breathing reflex is stimulated not directly by the absence of oxygen but indirectly by the presence of carbon dioxide. A result is that, at high altitudes, oxygen deprivation can occur in unadapted individuals who do not consciously increase their breathing rate.
The human appendix is a vestigial organ thought to serve no purpose. Appendicitis, an infection of this organ, is a certain death without medical intervention. "During the past few years, however, several studies have suggested its immunological importance for the development and preservation of the intestinal immune system."
Barely used nerves and muscles, such as the plantaris muscle of the foot, that are missing in part of the human population and are routinely harvested as spare parts if needed during operations. Another example is the muscles that move the ears, which some people can learn to control to a degree, but serve no purpose in any case.
The common malformation of the human spinal column, leading to scoliosis, sciatica and congenital misalignment of the vertebrae. The spinal cord cannot ever properly heal if it is damaged, because neurons have become so specialized that they are no longer able to regrow once they reach their mature state. The spinal cord, if broken, will never repair itself and will result in permanent paralysis.
Almost all animals and plants synthesize their own vitamin C, but humans cannot because the gene for this enzyme is defective (Pseudogene ΨGULO). Lack of vitamin C results in scurvy and eventually death. The gene is also non-functional in other primates and in guinea pigs, but is functional in most other animals.
Crowded teeth and poor sinus drainage, as human faces are significantly flatter than those of other primates and humans share the same tooth set. This results in a number of problems, most notably with wisdom teeth, which can damage neighboring teeth or cause serious infections of the mouth.
The structure of humans' eyes (as well as those of all vertebrates). The retina is 'inside out'. The nerves and blood vessels lie on the surface of the retina instead of behind it as is the case in many invertebrate species. This arrangement forces a number of complex adaptations and gives mammals a blind spot. A better structure for the eye would be to have the optic nerve connected to the side of the retina that does not receive the light, as is the case in cephalopods.
In the Africanlocust, nerve cells start in the abdomen but connect to the wing. This leads to unnecessary use of materials.
Intricate reproductive devices in orchids, apparently constructed from components commonly having different functions in other flowers.
The existence of unnecessary wings in flightless birds, e.g. ostriches.
The route of the recurrent laryngeal nerve is such that it travels from the brain to the larynx by looping around the aortic arch. This same configuration holds true for many animals; in the case of the giraffe, this results in about twenty feet of extra nerve.
The enzyme RuBisCO has been described as a "notoriously inefficient" enzyme, as it is inhibited by oxygen, has a very slow turnover and is not saturated at current levels of carbon dioxide in the atmosphere. The enzyme is inhibited as it is unable to distinguish between carbon dioxide and molecular oxygen, with oxygen acting as a competitive enzyme inhibitor. However, RuBisCO remains the key enzyme in carbon fixation, and plants overcome its poor activity by having massive amounts of it inside their cells, making it the most abundant protein on Earth.
Sturdy but heavy bones, suited for non-flight, occurring in animals like bats. Or, on the converse: unstable, light, hollow bones, suited for flight, occurring in birds like penguins and ostriches, which cannot fly.
Various vestigial body parts, like the femur and pelvis in whales (evolution says the ancestor of whales lived on land).
Many species have strong instincts to behave in response to a certain stimulus. Natural selection can leave animals behaving in detrimental ways when they encounter a supernormal stimulus - like a moth flying into a flame.
Plants are green and not black, as chlorophyll absorbs green light poorly, even though black plants would absorb more light energy.
Whales and dolphins breathe air, but live in the water, meaning they must swim to the surface frequently to breathe.
Several generic philosophical criticisms can be directed towards the first premise of the argument – that a Creator deity would have designed things 'optimally'. The argument hinges on an assumption that the human concept of 'optimal design' is the same as that of a theistic god. This is, in effect, the argument for the incomprehensibility of the Abrahamic GodYahweh in the Book of Job:
Then the LORD answered Job out of the whirlwind, and said, Who is this that darkeneth counsel by words without knowledge? Gird up now thy loins like a man; for I will demand of thee, and answer thou me. Where wast thou when I laid the foundations of the earth? Declare, if thou hast understanding. Who hath laid the measures thereof, if thou knowest? Or who hath stretched the line upon it? Whereupon are the foundations thereof fastened? Or who laid the corner stone thereof, when the morning stars sang together, and all the sons of God shouted for joy?
The Book of Job goes on to list a number of aspects of the world that seem wonderful or miraculous beyond human understanding. The claim is that, if humans have no understanding of how the wonders of the world were created, they cannot fully understand the things that appear flawed.
Optimal design engineering and trade-offs
Others argue that the observed suboptimality in one system or another is intentional, as a trade-off to improve overall optimal design.
While the appendix has been previously credited with very little function, research has shown that it serves an important role in the fetus and young adults. Endocrine cells appear in the appendix of the human fetus at around the 11th week of development, which produce various biogenic amines and peptide hormones, compounds that assist with various biological control (homeostatic) mechanisms. In young adults, the appendix has some immune functions.
Creationist Jonathan Sarfati and ophthalmologist Peter Gurney have both published articles on the Creation Ministries International website which disagree that the human eye is poorly designed, arguing that alternative arrangements would have further complications and that the human eye actually works very well.
Responses to criticism
In addition, the plantaris muscle does atrophy. Its motor function is so minimal that its long tendon can readily be harvested for reconstruction elsewhere with little functional deficit. "Often mistaken for a nerve by freshman medical students, the muscle was useful to other primates for grasping with their feet. It has disappeared altogether in 9 percent of the population."
In response to the claim that uses have been found for "junk" DNA, proponents note that the fact that some non-coding DNA has a purpose does not establish that all non-coding DNA has a purpose, and that the human genome does include pseudogenes that are nonfunctional "junk", with others noting that some sections of DNA can be randomized, cut, or added to with no apparent effect on the organism in question. The original study that suggested that the Makorin1-p1 served some purpose has been disputed. However, the original study is still frequently cited in newer studies and articles on pseudogenes previously thought to be nonfunctional.
As an argument regarding God
The argument from poor design is sometimes interpreted, by the argumenter or the listener, as an argument against the existence of God, or against characteristics commonly attributed to a creator deity, such as omnipotence, omniscience, or personality. In a weaker form, it is used as an argument for the incompetence of God. The existence of "poor design" (as well as the perceived prodigious "wastefulness" of the evolutionary process) would seem to imply a "poor" designer, or a "blind" designer, or no designer at all. In Gould's words, "If God had designed a beautiful machine to reflect his wisdom and power, surely he would not have used a collection of parts generally fashioned for other purposes. Orchids are not made by an ideal engineer; they are jury-rigged...."
The apparently suboptimal design of organisms has also been used by theistic evolutionists to argue in favour of a creator deity who uses natural selection as a mechanism of his creation. Arguers from poor design regard counter-arguments as a false dilemma, imposing that either a creator deity designed life on earth well, or flaws in design indicate the life is not designed. This allows proponents of intelligent design to cherry pick which aspects of life constitute design, leading to the unfalsifiability of the theory. Christian proponents of intelligent design as evidence of the existence of the Abrahamic GodYahweh can claim that good design indicates the creative intelligence of their God, while poor design indicates corruption of the world as a result of free will that caused the Fall (Genesis 3:16 has Yahweh saying to Eve "I will increase your trouble in pregnancy").
^"Nervous System Guide by the National Science Teachers Association." Nervous System Guide by the National Science Teachers Association. National Science Teachers Association, n.d. Web. 7 Nov. 2013. <"Archived copy". Archived from the original on 2013-10-01. Retrieved 2013-11-07.CS1 maint: archived copy as title (link)>
^Ohta Y, Nishikimi M (October 1999). "Random nucleotide substitutions in primate nonfunctional gene for L-gulono-gamma-lactone oxidase, the missing enzyme in L-ascorbic acid biosynthesis". Biochim. Biophys. Acta. 1472 (1–2): 408–11. doi:10.1016/S0304-4165(99)00123-3. PMID10572964.
^"Wisdom Teeth." American Association of Oral and Maxillofacial Surgeons (AAOMS). AAOMS, n.d. Web. 7 Nov. 2013. <"Archived copy". Archived from the original on 2013-11-10. Retrieved 2013-11-07.CS1 maint: archived copy as title (link)>.
^Nave, R. "The Retina." of the Human Eye. N.p., n.d. Web. 7 Nov. 2013. <"Archived copy". Archived from the original on 2015-05-04. Retrieved 2015-06-03.CS1 maint: archived copy as title (link)>.
^"Squid Brains, Eyes, and Color." Squid Brains, Eyes, and Color. N.p., n.d. Web. 7 Nov. 2013. <"Archived copy". Archived from the original on 2013-11-11. Retrieved 2013-11-07.CS1 maint: archived copy as title (link)>.