its very simple lootekukur.....!!!!!!!!!!!!here Darwin's theroy of evolution comes into play..according to theroy...when any parts or organ of body is less functional or is very inactive in day to day life, then there is always a possibilty that organ or parts will be very inactive nad less functional and finnally dissapered...examples little finger of the leg....appendix., tail of a snake........for more ..log into knowfacts.com