The stone age began around 2.5 million years ago and was divided into three main eras: the Paleolithic era from 2.6 million to 15,000 BC when early humans first used stone tools for hunting; the Mesolithic era from 9600 to 5000 BC when tools became finer; and the Neolithic era from 6000 to 2500 BC when humans began domesticating animals and farming and started creating cave paintings.