As we all know that every organ, tissue and cell of our body has been allotted a specific role that unites our whole body as a single functional unit. But do you know there are some parts present in our body that have no role and if removed will cause no hindrance in our body’s normal functionality? well, these organs are commonly known as the Vestigial Organs. Let us try to understand them with classical examples that you can relate with.
Definition of Vestigial Organs
Vestigial Organs are those organs or tissues that are no longer in use by humans or other organisms but their structural remains still exist in the body. These non-functional parts of an organism’s body are called vestigial organs.
Or simply we can say, these are those parts of our body that were once in use by our ancestors but due to many factors (internal and external), these organs became non-functional but are still present in our body. Therefore these organs can be called the old machinery of our body with no actual roles. Although most of the vestigial organs are functionless in some cases it is seen that these organs may sometimes develop some new functions or retain their old functions. Darwin named vestigial organs as ‘Rudiments’. He also listed a number of rudiments in the human body including wisdom teeth, appendix, tail bone etc in his book ‘The Descent of Man and Selection in Relation to Sex’ (1890).
Reason for vestigiality
Now the question arises why some organs of our body became vestigial while others did not? Most of the questions related to the changes in the body of organisms in subsequent generations with time can be answered by one concept, that is, evolution. Evolution is a continuous process that brings changes in the body of an organism. It can be simply understood by the changes that happen in a population in order to adapt to the changing environment. Evolution is a constant process that is happening from the time organisms first started living on earth and it is the reason why we humans were able to evolve as the most intelligent species on the earth. But it must also be understood that evolution is not always a positive/helpful process.
There are many records around us like fossils, homologous and analogous organs, genome, carbon dating, pedigree maps etc that are proof for evolution. Another great proof of evolution is the vestigial organs. Therefore we can say that vestigiality is a result of evolution. We can also understand that vestigial organs are the remains/residues of our ancestors in our body. Robert Wiedersheim published a book in 1893 in which he listed 86 human vestigial organs. The name of the book was ‘The Structure of Man’ and it was based on human anatomy.
But how does evolution works on changing these organs from functional to non-functionals? Following are a list of the factors that can affect the functionality of an organ/tissue with the course of evolution:
- Natural Selection
- Environmental factors
Examples of Vestigial Organs
Following are some examples of vestigial organs:
Human ancestors used wisdom teeth to chew the plant tissues and raw meat. Due to less developed digestive system, humans needed a strong chewing mechanism to grind the food properly before it reached the stomach. But with the evolution of the human digestive system, the necessity for the wisdom teeth become less and now they’re completely useless and even harmful to some. Also, human ancestors used to feed mainly on the plants which contain cellulose which is not digestible by human’s digestive enzymes. Therefore strong teeth were needed to chew such materials.
If you have ever noticed, the shape of the foetus of all the vertebrates is similar in the initial stages. Tailbone, also known as Coccyx is ruminant of the tail from our ancestors. Other mammals like monkeys that are close relatives of humans do not have tails as a vestigial but as functional organ because it provides balance to their body.
But when humans learned to walk on their hindlimbs, the tail was of no use to and therefore it was reduced and ultimately in the modern humans, the tail bone got fused with the vertebrae. Therefore coccyx or tailbone is a vestigial organ in humans.
An appendix is a small pouch-like structure present in the lower right of the abdomen attached to the large intestine. The original function of the appendix is unknown but in plant-eating vertebrates, it is a functional part of the digestive system but not in humans. Some scientists believe that appendix is home for some good bacterias that help the body fight diarrhoea. The human appendix is a vestigial organ and every one out of twenty people have to get it removed by a surgery called Appendectomy. This surgery is performed when the appendix gets clogged with unwanted material like bacterias, faecal matter or get cancer. This condition is called Appendicitis and leads to inflammation of the appendix. This is a very painful condition and doctors mostly advice for the appendectomy. Even after the removal of the appendix, patients digestive system works just fine which again prove that vestigial organs are not important for our body.
Preauricular sinus and cyst
Preauricular sinus and cyst is a condition in some people who are born with an extra hole which is present on the meeting point of the ear cartilage and face. As the theories propose that evolution started from aquatic life and we were all once marine animals, these holes are therefore considered as a ruminant of gills by some scientists.
Some snakes like Python and Boa have hind legs that are buried in their skin near their tail. This is excellent evidence of the evolution of snakes as it is believed that snakes are descendants of lizards. These legs have no function as known and are hence vestigial.