Elephants are the largest terrestrial animals, it is befitting for them to have large ears. The Elephant ears serve may functions, this may be the reason why it has evolved over time to carry out these functions.
Elephants generate a lot of body heat. They are not as lucky as human that have sweat glands.
The ear is use to get rid of body heat. The ear is one of the parts that is close to the outside of the Elephant. Heat moves towards the ear which normally has low heat. Elephants flap their ears to get rid of the heat. They spread their ears wide to signal threats.
Scientists also believe that the large ears also serve as a funnel for sound to get into the inner ear.