Scientifica Philosophica !!!: Useless organs

Today I became lesser wiser by 3 counts. I had my 3 wisdom tooth removed. E

ven if little late, I realized that, it is 'wise to be less wise'. It started as a pain few weeks back and doctor diagnosed it as desparate attempt of an horizontally impacted wisdom tooth to come out. According to him wisdom teeth are not used for chewing or any known useful purpose and suggested to extract it before it cause any serious health hazard. I decided to heed to his advice and also to remove the remaining 2 too, just to avoid some trouble in future.

Reading about the issue I realized that more than 4 million teens in America remove their wisdom teeth every year. It is a billion dollar industry in US. However, such prophylactic odontectomy (removal of asymptomatic teeth) faces criticism from some sections of health care professionals also who believe that wisdom tooth need to be removed only if it casuses any syptoms. Apparently wisdom teeth do not perform any useful purpose other than providing financial support to the maxillo facial surgeons around the world. However, it is hard to believe that nature designed the 3rd pair of molars only to make dentists wealthy. Mother nature is famous for her frugality. In a highly

evolved species it is hard to find any ezymatic pathway or organ that is useless. Generally, millions of years of evolution is sufficient to get rid of the unwanted proteins or genes to save the ATPs that is required for the synthesis of them, let aside an entire anatomical structure like a teeth. Then the question is if the wisdom teeth serve no useful function why is it still preserved in highly evolved species like human beings ??

A breif review of the literature revealed that humans share the same dental formula as gorillas and orangutans (2/2, 1/1, 2/2, 3/3). This probably would be from a common ancestor of distant past. Early humans used to have lots of fibrous vegatables in the diet which demanded a strong molar teeth. Moreover, the tooth decay also would have been a major problem in ancient societies resulting in the loss of teeth pretty early in life which gave enough room for late coming tooth. (Wisdom tooth got its name since it erupt in the age of 16-30 years, a period when women and men are supposed to be wise; women at 16 and men at 30, I guess !!!) . But, in modern societies, we consume mostly cooked food which a are relatively soft when compared to the hard food of our ancestors. Also, the improvement in dental hygeine effectively reduced the tooth decay problem. All these together made the third molar a vestigeal structure. Another, but similar explanation is that, the change in diet along with increase in the brain size in new generations, resulted in the selection of small jaw to give space for enlarged cranium. However, it is hard to find the selection pressure worked in that process. ie, how a shift to soft diet help in selection of small jaw size ? For Darwinian forces to work, in order to a trait to be selected in a population, it should have differential reproductive advantage (like the potential mate selectively choose the small sized jaw person as partner), as of now there is no record for such a selection in recent history.

Interestingly, Darwin himself have taken up this issue in his famous book "The descent of Man and selection in relation to sex' and used it as a supportive evidence of evolution. So, in evolutionary terms, the third molars were retained, eventhogh they did not serve any useful fucnitons because there were no selection pressure acting against them. So a plausible explanation could be the combination of brain size theory and the practice of better dental care, which made the third molar not required for any useful functions. Now are there any other such useless organs in our body ? The answer is a big Yes !! Discover magazine has published an interesting list of organs which serve no obvious useful function in the body, other than wisdom teeth...
APPENDIX : This narrow, muscular tube attached to the large intestine served as a special area to digest cellulose. Annually, more than 300,000 Americans have an appendectomy.

BODY HAIR: Brows help keep sweat from the eyes, and male facial hair may play a role in sexual selection, but apparently most of the hair left on the human body serves no function.

COCCYX: These fused vertebrae are all that’s left of the tail that most mammals still use for balance and communication. Our hominid ancestors lost the need for a tail before they began walking upright.

MALE NIPPLES: Lactiferous ducts form well before testosterone causes sex differentiation in a fetus. Men have mammary tissue that can be stimulated to produce milk.
NECK RIB: A set of cervical ribs—possibly leftovers from the age of reptiles—still appear in less than 1 percent of the population. They often cause nerve and artery problems.
THIRD EYELID: A common ancestor of birds and mammals may have had a membrane for protecting the eye and sweeping out debris. Humans retain only a tiny fold in the inner corner of the eye.

PALMARIS MUSCLE: This long, narrow muscle runs from the elbow to the wrist and is missing in 11 percent of modern humans. It may once have been important for hanging and climbing. Surgeons harvest it for reconstructive surgery.
ERECTOR PILI: Bundles of smooth muscle fibers allow animals to puff up their fur for insulation or to intimidate others. Humans retain this ability (goose bumps are the indicator) but have obviously lost most of the fur.

PLANTARIS MUSCLE: The muscle was useful to other primates for grasping with their feet. It has disappeared altogether in 9 percent of the population.
THIRTEENTH RIB: Our closest cousins, chimpanzees and gorillas, have an extra set of ribs. Most of us have 12, but 8 percent of adults have the extras.
MALE UTERUS: A remnant of an undeveloped female reproductive organ hangs off the male prostate gland.