Once upon a time, there were Vestigial organs:They are no more rudimentary

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Do an appendix, coccyx, tonsils, Pinna and wisdom teeth together click something in your mind? Right they were once considered useless and redundant and could be chopped away when causing trouble. A body structure that has lost its function and considerably reduced in size were recognized as rudimentary or vestigial structures and were used as evidence of evolution.  These organs were considered to have been better developed and had significant functions in the past and in our ancestors but have lost the function and structure in the present; in the modern animals. Vestigial structure may have lost a salient function but may retain some other function.

The idea of vestigial came with Darwin’s theory of evolution. Darwin felt that appendix was vestigial as it was smaller in comparison to caecum of monkeys. Darwin cites it as an example of evolution that in course of man’s evolution the use of caecum declined and the appendix as caecal appendage has grown much smaller in size due to No function or disuse as man evolved from herbivorous ancestors. Darwin’s followers towed the same line of thought and ended up identifying 180 vestigial structures in human’s by1890 (Wiedersheim). This pile up of use less organs was argued to be proof of evolution. The argument given is that Evolution being an imperfect process; the redundant organs do not get removed but remain as reduced relics. With environmental selection against certain structure, some forms persist even if they are not used, these structures may have homologous functional structures in other organisms. Darwin held that just like silent letters in a word which offer clues to origin of word; these organs are also testimony to the origin of species. 

The evolutionary presumption that the vestigial organs served no function was dangerous as these organs were surgically removed whenever infected or diseased.

But it is time we change our outlook, more and more of these organs /structures are found to be functional. The question bothering researchers was why would nature invest so much to carry baggage of our ancestors even if it is rudimentary in form. It was more of ignorance of their function and the insufficient technology that has obscured the functional significance of these so called rudimentary organs. Findings of research in the field of anatomy and physiology have shown these organs to be completely functional.

The appendix sits between the nearly sterile ileum at the end of the small intestine and the caecum at the entrance to the large intestine. Appendix is part of the immune system with a high bacterial content. Far from useless, the organ is actually a storehouse of beneficial bacteria that help us digest food.  Appendix is very important for people for repopulating intestines with helpful bacteria after a diarrheal illness.

The tonsils have a similar immune-function in the entrance of the pharynx.

The pineal gland is now considered to be master of master’s gland Pituitary. Pineal secretes melatonin that regulated circadian rhythm and influences other hormones

Thymus is a part of immune system related to T cells. And spleen helps in spotting infections and filters out red blood cells that are damaged or old, recently it has been found to be helpful in healing hearts. And many more of the so called vestigial organs found functions thanks to the efforts of modern day researchers.

Don’t forget the Junk DNA; during the sequencing of genomes, our genetic material showed that only a small percentage to the tune of 1.2% of our entire genetic material of 3 billion base pairs can code for functionality. Rest of the genetic material is called non- coding. Instead of relegating it to JUNK or vestigial; scientist are finding profound functions of this redundant DNA as well.

 

References:

 Wiedersheim, R. (1893) The Structure of Man: An Index to His Past History. Second Edition. Translated by H. and M. Bernard. London: Macmillan and Co. 1895. p.xi

DENNIS P. BURKITT, “The Aetiology of Appendicitis,” British Journal of Surgery, December 2005.

Comparative anatomy and phylogenetic distribution of the mammalian cecal appendix

2009 · Journal of Evolutionary Biology

 

Article by:

Dr. Shashi Singh

Chief Scientist

CSIR-Centre for Cellular and Molecular Biology

Hyderabad – 500007

Email: shashis@ccmb.res.in