Why do African elephants have such big ears?

Elephants are the largest land animals and generate a lot of body heat, but they cannot sweat like humans. Their ears are thin and packed with blood vessels close to the surface. As warm blood passes through, heat escapes into the air, and flapping the ears speeds up the cooling. African elephants live in hot, open savannas and have much larger ears than Asian elephants, which live in shadier forests. Elephants also use their ears to communicate, spreading them wide to look bigger when threatened.