Argument from poor design

Artist's representation of an ectopic pregnancy. Critics cite such common biological occurrences as contradictory to the 'watchmaker analogy'.

American scientist Nathan H. Lents published his book on poor design in the human body and genome in 2018 titled, Human Errors. The book ignited a firestorm of criticism from the creationist community[7][8] but was well received by the scientific community and received unanimously favorable reviews[9] in the dozens of non-creationist media outlets that covered it.

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.[10]
• The existence of the pharynx, a passage used for both ingestion and respiration, with the consequent drastic increase in the risk of choking.
• 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."[11]
• Tinnitus, a phantom auditory sensation, is a maladaptation resulting from hearing loss most often caused by exposure to loud noise.[12] Tinnitus serves no practical purpose, reduces quality of life, may cause depression, and when severe can lead to suicide.[13]

• Barely used nerves and muscles, such as the plantaris muscle of the foot,[14] 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.[15]
• 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.[16]
• Almost all animals and plants synthesize their own vitamin C, but humans cannot because the gene for this enzyme is defective (Pseudogene ΨGULO).[17] 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.[18]
• The prevalence of congenital diseases and genetic disorders such as Huntington's disease.
• The male urethra passes directly through the prostate, which can produce urinary difficulties if the prostate becomes swollen.[19]
• Crowded teeth and poor sinus drainage, as human faces are significantly flatter than those of other primates although 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.[20]
• The structure of human 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.[21] Having the optic nerve connected to the side of the retina that does not receive the light, as is the case in cephalopods, would avoid these problems.[22] Lents and colleagues have proposed that the tapetum lucidum, the reflective surface behind vertebrate retinas, has evolved to overcome the limitations of the inverted retina,[23] as cephalopods have never evolved this structure.[24] However, an 'inverted' retina actually improves image quality through müller cells by reducing distortion.[25] The effects of the blind spots resulting from the inverted retina are cancelled by binocular vision, as the blind spots in both eyes are oppositely angled. Additionally, as cephalopod eyes lack cone cells and might be able to judge color by bringing specific wavelengths to a focus on the retina, an inverted retina might interfere with this mechanism.[26]
• Humans are attracted to junk food's non-nutritious ingredients, and even wholly non-nutritious psychoactive drugs, and can experience physiological adaptations to prefer them to nutrients.

• In the African locust, nerve cells start in the abdomen but connect to the wing. This leads to unnecessary use of materials.[10]
• Intricate reproductive devices in orchids, apparently constructed from components commonly having different functions in other flowers.
• The use by pandas of their enlarged radial sesamoid bones in a manner similar to how other creatures use thumbs.[10]
• The existence of unnecessary wings in flightless birds, e.g. ostriches.[27]
• 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,[28] 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.[29]
• 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 indicates the ancestors of whales lived on land).
• Turritopsis dohrnii and species of the genus Hydra have biological immortality, but most animals do not.
• 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.
• Albatrosses cannot take off or land properly.

Intelligent design proponent William Dembski questions the first premise of the argument, claiming that "intelligent design" does not need to be optimal.[30]

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.[31]

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.[32] The original study that suggested that the Makorin1-p1 served some purpose[33] has been disputed.[34] However, the original study is still frequently cited in newer studies and articles on pseudogenes previously thought to be nonfunctional.[35]