Elephant's ancestor is a term used to refer to two extinct species of mammals, the mastodon and the stegodon. The mastodon was a large, elephant-like mammal that lived during the Pleistocene epoch, while the stegodon was a smaller, more primitive relative of the modern elephant. Both species were herbivores and had long tusks and thick hides. They are believed to have gone extinct around 10, 000 years ago due to climate change and human hunting.