Chapter 5: Interrelation through Vestigial Organs
Section I: Vestigial Organs
The final piece of living evidence that I have to offer is that of vestigial organs. In a very real sense, reversionary organs are equally vestigial, or useless. But I have separated the two as a way to help understanding of them both. A "vestigial organ" be may defined as an organ which serves no purpose to an organism. Reversionary organs are the same, but the difference that I have between this and the last chapter is that vestigial organs always appear in a species, whereas reversionary organs appear in only some cases.
As far as personal experience goes, it is undeniable that many of us come into contact with vestigial organs, or can identify them on ourselves personally. For instance, males have nipples, an organ which serves a purpose to females but is entirely useless to men. [*1] In domestic cows, there are four developed mammae, capable of producing milk and there are two other nipples which are rudimentary and serve no purpose -- yet there is a rare occurrence where these two rudimentary nipples become well developed and produce milk. [*2] So, in the case of domestic cows, not only are they vestigial, but in some instances, they show cases of reversion. It is not deniable that wisdom-teeth are vestigial, in that many cases, not only do they fail to appear, but once they do appear, they surgical must be removed. Though wisdom-teeth are vestigial in the case of European humans, in the Melanian races, the wisdom-teeth are furnished with three separate fangs and are generally sound. [*3] Professor Schaaffhausen argues that the reason why wisdom-teeth are vestigial to European humans is due to the fact that the jaw is shorter in European humans, and the reason for this occurrence is believed that Europeans eat soft, cooked food, that extra teeth become rudimentary. [*4] To quote one scientific encyclopedia...
The logger-headed duck of South America and the domestic Aylesbury duck cannot fly when they are adults with their wings, though their young are capable of flight. [*6] The ostrich is equipped with wings, yet it is entirely incapable of flying. [*7] In many of the male dung beetles, the anterior tarsi, or the feet, have fallen off at an early stage in their development, to the point where it is rare to find one with feet. [*8] In other insects, such as the Onites apelles and the Ateuchus (or the sacred beetle of the Egyptians), the feet are so habitually lost, that according to most records, they are described as not having them. [*9] In Madeira, a river in northwest Brazil, out of 550 species of beetles, there are 200 beetles which have wings that are so deficient, that they are incapable of flight, and even those who are amateur Naturalists in almost any continent will be able to confess to discovering such a creature. [*10] Moles, a creature which burrow underneath the earth's surface, often have eyes which are covered in fur and hair; in South America, the tuco-tuco (or Ctenomys), which are more subterranean than the mole, are frequently blind, though they are born with eyes. [*11] Several creatures, inhabiting the caves of Carniola and of Kentucky, are known to be blind though endowed with eyes. [*12] In some crabs, known to inhabit extremely dark places such as cave, the foot stalk -- which typically supports the eye -- still exists, though the eyes are gone. [*13] Caverats, which typically are equipped with large eyes, are typically blind, but after being exposed to light for about a month, they acquire a dim perception of objects. [*14] The Bathyscia, an insect species, are known to appear in several varieties; typically, those that inhabit caves are a sub-species, typically appearing blind and reproducing blind offspring, whereas another sub-species, normally inhabiting shady rocks not far from these caves, are known to be endowed with full vision. [*15] In the human fetus, on the neck there are slits, representing gills, and there are arteries developing on the neck showing where these slits would be, yet as the fetus develops both the slits and arteries disappear. [*16] In the world untainted by mankind's touch, the wild chickens flee from the sight of dogs, yet in domesticated chickens, this instinct has been wholly lost. Furthermore, when a wild hen feels danger, she lets off a danger call as she flies away and her chicks hide in the thickets or grass nearby. In domesticated chickens, they still have this instinct, but it is useless, as they are incapable of flight. [*17]
For many snakes, they are equipped with a functionless, underdeveloped second lung. [*18] Snakes in the family Boidae (boas and pythons) occasionally don't use both lungs, though they have a pelvis and extremely poorly developed hind-legs; snakes in the family colubridae (colubrid snakes), the left lung is either absent or extremely underdeveloped. [*19] The bastard wing, a tuft of feathers on the fifth digit of many birds, is highly rudimentary, and in some cases it cannot be used for flight. [*20] When whales are still a fetus, they have been observed to developed teeth, which disappear by the time they are adults. [*21] Unborn calves are a similar situation, where they develop teeth in their jaws that never cut through the gums. [*22] In some beetles that are closely allied to flying insects, underneath the wing covers, there appears to be two membranes connected together, not much unlike those of the flying insects. [*23] The Apteryx is a bird from New Zealand, and though it is winged, it is incapable of flight. [*24] In the order of Dipnoi, there is an eel-shaped fish with vestigial organs of the axis of a fin, with the lateral rays of branches aborted. [*25] Manatees are known to have nails on their flippers. [*26] In regards to vestigial organs appearing in domestic organs, I will here quote Charles Darwin...
The os coccyx of humans serves no purpose, though it is an internal tail of human beings. It is constructed in the same manner that the os coccyx of apes are developed, and the muscles and vertebrae of it are quite similar to that of the tails of lower animals. [*28] There are some who will argue that the os coccyx is not vestigial and that it serves a purpose. How would they respond, then, to those human beings whose os coccyx has developed fully into a tail, and have no problems functioning without an internal tail? Many animals are capable of twitching their skin, such as horses, and humans retain some of these muscles, such as the platysma myoides, which are developed on the back of the neck. [*29] It is not deniable that certain humans are capable of moving their ears forward, backward, downward, and upward, muscles which serve no more purpose than if we had muscles to move our nose. [*30] To quote Darwin, "The power of erecting and directing the shell of the ears to the various points of the compass, is no doubt of the highest service to many animals, as they thus perceive the direction of danger; but I have never heard, on sufficient evidence, of a man who possessed this power, the one which might be of use to him." [*31] The ears of the chimpanzee and the orangutan are in a similar condition of man, with underdeveloped muscles, and it is rare for a sighting of a such a primate moving their ears. [*32] It has been stated that the ear lobe is distinct only to humans, but a rudiment of it may be found in the gorilla, and in some individuals of African descent, it is absent altogether. [*33] Humans contain a secondary set of eyelids, known as the "semilunar fold" (scientific name: plica semiluna'ris conjuncti'vae), and this can be found in many of the lower animals, yet in mankind, there is no muscle adaptated for moving this set of eyelids. [*34] The sense of smell in humans, compared to that of other animals, is considerably underdeveloped and of almost no practical use; but, it is good to take into consideration that aboriginal natives are capable of identifying someone in the dark by their smell. [*35] For some individuals of European descent, there are tufts of hair on the shoulder; though there tends to be a great deal of variability in the placement of hair on the body of humans, typically it is common for a body to be naked of hair, but the body hair can develop into thick, long, dark, and coarse hair -- a type of vestigial organ from our predecessors. [*36] Some holly-trees, for example, will bear only male seeds, yet they are equipped with a rudimentary pistil, which can only be used by female trees for reproduction. [*37] It is doubted by no one that webbed feet are an advantage for aquatic animals, yet upland geese and the frigate bird have this adaptation, and they are non-aquatic, though there is reason to believe there ancestors are. [*38] In the human digestive system, as in the digestive system of many other organisms, there is a caecum, a pouch connected to the intestines. Though present in many lower organisms, in humans it is extremely small, while in the koala it is thrice its size, and in humans, there are instances where it is entirely absent altogether. [*39] Not only is it useless like the appendix, but like the appendix, it can be a cause of death through cancer or inflammation. [*40] In the human jaw, canine teeth seem to serve no purpose at all. The initial purpose is believed to be a sort of fighting mechanism, but since man developed tools and weapons, it became a vestige, and ancient skulls have been found where the canine teeth are enormous. [*41] To quote Charles Darwin...
These vestigial organs serve no purpose, but in many instances, they are existing remnants of species we are related to. In ending this section, I will quote Darwin once again...
*1. Origin of the Species, by Charles Darwin, 1859, Sixth Edition, chapter 14. The Descent of Man, by Charles Darwin, 1871, chapter 1.