Imperfections of Nature
A common line of logic presented as "evidence" for evolution is the argument that nature is imperfectly designed. It is therefore argued that evolution should be accepted by default. This is not scientific evidence. This is philosophy that masquerades as science. One cannot argue the validity of a scientific theory by arguing that God does't exist. Many books and articles have been written attempting to prove evolution by attempted disproof of God.
There are many examples in nature that are cited as examples of imperfections, and are used as evidence for evolution. The human eye has six muscles to control its movement when it only requires three. Most mammals can synthesize their own vitamin C, while humans cannot. The pharynx is used for both digestion and respiration, which can result in choking and life-threatening aspiration into the lungs. The urethra in males serves as a common conduit for both excretion of urine and copulation. This is a sub-optimal design in the minds of some. Man's propensity to diseases is also argued as evidence of poor design. The presence of wisdom teeth is believed to indicate a "mistake" in design, presumed to be left over from herbivorous ancestors, thus providing evidence against divine creation. An adult male's prostate commonly enlarges, causing urinary obstruction. An embryo can implant in the fallopian tube and result in a life-threatening ectopic pregnancy. The prevalence of degenerative conditions such as herniated vertebral discs and osteoarthritis is used as evidence against intelligent design. The existence of congenital diseases such as Huntington's chorea and inborn errors of metabolism are also presented as evidence against intelligent creation. The recurrent laryngeal nerve travels from the brain to the larynx by redundantly looping around the aortic arch. This results in an unnecessary 20 extra feet of nerve in giraffes.
Many articles have been published which refute that nature is poorly designed. In the case of the recurrent laryngeal nerve, for example, anatomic and embryologic reasons have been described which suggest that this circuitous route is logical from a standpoint of intelligent creation.
Even if it can be shown that nature is imperfectly designed, such observations cannot be presented as scientific evidence. The "evidence" amounts to nothing beyond the philosophical opinions of secular thinkers.
In this video, Dr. Richard Dawkins believes he is providing scientific evidence for evolution as he observes an anatomist dissect the recurrent laryngeal nerve. Rather than attempt to demonstrate how evolution could create the great complexities of a nerve to control the muscles of the larynx, Dawkins instead chooses to mock the idea of an "intelligent designer" having created nature as it is.
Although "imperfections of nature" are commonly cited as compelling evidence for evolution, this argument should be excluded from scientific discussion, because this is not science.