When the first humans came to the Americas, the glacial climate of the Pleistocene was just beginning to lessen. In the Semi-arid north of Chile (from the Copiapó to the Aconcagua Valley) the melting of the ice left behind a land sprinkled with lakes and rushing rivers, increasing vegetation and concentrating herds of large land animals, now extinct, around these more verdant areas. Among these animals were the so-called megafauna, including mastodon, New World horses, swamp deer, early llama and Milodon.