In the fairly ordinary movie “Man of the Year”, comedian Robin Williams plays a TV host who, thanks to a chain of strange circumstances, becomes the President of the United States. During an election debate, Williams's character is asked what he thinks of the creationist theory of intelligent design. He answers: “If they talk about intelligent design, they should teach the idea of intelligent design. Just look at the human body: is it constructed intelligently? This is necessary: the waste processing plant is located next to the recreation area!”
Good point. Although it may seem that organisms are designed to fit into their environment, let's not flatter ourselves that this design is perfect. Each species is imperfect in its own way. Kiwis have useless wings, whales have a rudimentary pelvis, and our appendicitis is generally a treacherous organ.
A good example of an imperfect design is the flounder, whose popularity in cooking (for example, Dover sole) is partly due to its flat shape, because such fish is easier to carve. In general, there are about five hundred species of flat fish: halibut, turbot, flounder and their relatives—all of them belong to the flounder family. The Latin name of the fish order, Pleuronectiformes, means “floating on its side”, and this description is the key to the unfortunate design of flat fish. They are born as normal fish, swimming vertically, and their eyes are located on the sides of the body, which has the shape of a pancake. But a month after birth, something strange happens to the fish: one eye begins to move up. It moves along the skull until it reaches the second eye, and it produces a fish that has both eyes on the same side, left or right, depending on the specific species. The skull also changes shape, contributing to this movement, in addition, the color and fins change. As a result, the fish leans on the side that was left without the eye, so that both eyes are on top. It turns into a flat, masked sea-bottom dweller that preys on other fish. If the fish needs to swim, it swims on its side. Flounders are considered the most asymmetric vertebrates in the world; next time you go to buy fish, consider one of the representatives of this order.
If you wanted to design a flounder from scratch, you would act very differently. You would develop a fish like a stingray, which is flat from birth and lies on its stomach. You wouldn't waste your energy creating a fish that would have to become flat after birth by lying on its side, moving its own eye across the skull to the other side, and deforming the skull. Flounders are poorly constructed. However, this imperfect design is due to their evolutionary heritage. From the family tree of flounders, we know that flounders, like all members of the order, developed from “normal” symmetrical fish. Undoubtedly, they found some advantages in being able to lean on one side and live on the seabed, hiding from both predators and prey. Of course, this created a problem: the lower eye facing the bottom would become useless and vulnerable. To correct this, natural selection went a painful but accessible way: it moved the fish's eye and deformed its body.
One example of the worst natural construction is the recurrent laryngeal nerve of mammals. It goes from the brain to the larynx and helps us speak and swallow. The interesting thing is that it is much longer than necessary. Instead of going directly from the brain to the larynx, which in the human body is a distance of thirty and a half centimeters, the nerve follows a circular path: it goes down to the chest, wraps around the aorta and arterial ligament, and only then goes back up (recurrent!) to the larynx. As a result, the length of the recurrent laryngeal nerve is 90 cm. In giraffes, the nerve runs the same route, but it descends from the top to the bottom of the giraffe's long neck and then returns to the top: the distance is 4.5 m longer than if the nerve went straight!
The detour of the left recurrent laryngeal nerve in humans serves as proof of descent from a fish-like ancestor. In fish, the sixth gill arch, which later becomes the gills, is served by the sixth aortic arch. The fourth branch of the vagus nerve passes behind this arc. In adult fish, these structures remain part of the gill apparatus, bringing blood from the gills and performing innervation. However, in mammals, part of the gill arch has developed into the larynx. During this process, the larynx and laryngeal nerve remained connected, but the sixth gill arch on the left side of the body moved down into the thorax to become a non-functioning rudiment—the ligamentum arteriosum, the arterial ligament. Since the nerve remained behind this arch, but retained its connection with the neck, it was forced to develop a pathway in which it descends into the chest, wraps around the aorta and the remainder of the sixth aortic arch, and then returns up to the larynx. The circumference of this nerve does not look like evidence of intelligent creation, but becomes explicable only as the fruit of evolution, of descent from ancestors with a completely different body structure.
The path the recurrent laryngeal nerve follows is not only an example of imperfect construction, but can also be a maladaptive (harmful) sign. Excess length makes the nerve more vulnerable. For example, it can be damaged by a blow to the chest: you may have difficulty speaking or swallowing. However, the circumferential pathway of the recurrent laryngeal nerve makes sense if you understand how this nerve came to be. Like the aorta itself in mammals, it comes from the gill arches of our fish-like ancestors. At the initial stage of fetal development, when the embryo of all vertebrates is similar to fish, the nerve goes from the top down, along with a blood vessel of the sixth gill arch; this branch of the larger vagus nerve that descends along the back from the brain. In adult fish, the nerve remains in the same position, connecting the brain to the gills and helping them pump water.
In the course of human evolution, the blood vessel from the fifth gill arch disappeared, and the vessels from the fourth and sixth arcs moved down into the future torso to later become the aorta and the ligament connecting the aorta to the pulmonary artery. But the laryngeal nerve, which still remained behind the sixth gill arch, had to remain connected to the embryonic structures that became the larynx and remained close to the brain. As the future aorta moved back toward the heart, the laryngeal nerve was forced to move along with it. It would be more effective for the nerve to go around the aorta by disconnecting and reconnecting and thus following a more direct course. But natural selection did not allow this, because disconnecting and restoring the nerve is a step that reduces the fitness of the body. To keep up with the movement of the aorta in the posterior direction, the laryngeal nerve was forced to lengthen and become recurrent. This evolutionary route is repeated in the process of intrauterine development, because the structure of the nerves and blood vessels in the human embryo is initially the same as in the fish-like ancestor. In the end, the poor design remains with us.
Thanks to evolution, human reproduction is also full of design flaws. You already know that the lowering of the male testicles as a result of their origin from the gonads of fish leads to the appearance of weak spots in the abdominal wall, which can lead to hernias. Men have other vulnerabilities. In particular, they have a poorly designed urethra: it happens that it passes exactly in the middle of the prostate gland, which produces part of the sperm. To paraphrase the Robin Williams’s joke, the sewer runs directly through the recreation area. A substantial proportion of men in adulthood is developing prostate adenoma that compresses the urethra and makes the process of urination very painful. (It seems that for most of human evolution this problem has not been so acute, because few men reached 30 years old.) A smart designer would not pass a flexible, deformable tube through an organ that is prone to infection and tumor formation. In the course of evolution, these organs were formed this way because the mammalian prostate developed from the tissues of the urethra wall.
Women in terms of design imperfections are not too lucky either. During childbirth, the baby passes through the pelvis, and this painful and time-consuming process killed a huge number of mothers and babies before the advent of modern medicine. The problem is that because we have developed a large brain, the infant's skull has become very large relative to the entrance to the pelvis, which must remain narrow so that the person can walk effectively on two legs. This compromise leads to the difficulty and incredible pain of childbirth. If you were to design a female human, wouldn't you change the structure of her genital tract so that the birth canal opens in the lower abdomen instead of passing through the pelvic bones? Just imagine how much easier it would be to give birth! However, humans are descended from oviparous or viviparous creatures that produced offspring through the pelvis and much less painfully than we do. So, we are prisoners of our own evolutionary history.
And would an intelligent creator create a small gap between the ovary and the fallopian tube, so that the egg must necessarily travel this distance before going through the tube and implanting itself in the uterus? At times, the fertilized egg does not manage to make this journey safely, and it attaches to the abdominal cavity. As a result, an ectopic pregnancy occurs, which is almost always fatal for the child and, without surgery, for the mother, too. This gap is our inheritance from fish-like and reptilian ancestors who laid eggs directly from the ovary to the outside environment. The fallopian tube is an imperfect connecting element, because it developed later in mammals as an additional structure.
Some creationists argue that imperfect construction may not serve as an argument in favor of evolution. In their view, a supernatural divine creator could, despite his divinity, create imperfect features. Yes, the supreme creator may well have been guided by motives that are incomprehensible to us. But the particularly poor constructions that we observe in nature can only be explained if they are descended from ancestral forms. If the divine creator, when creating biological species, was still guided by some comprehensible reasons, then one of them must have been to deceive biologists and make the organisms look as if they were formed in the course of evolution.