Later, Petén became the heartland of the Maya Classic Period (c. 200 – 900 CE). At its height around 750 it is estimated that the Petén Basin was home to several million people, being one of the most densely populated regions of the world at the time. Some areas are estimated to have had ca 2,000 people/km². Mesoamerican agriculture was very extensive, and there is some evidence suggesting that the land was depleted by unsustainable overfarming, resulting in a famine which was an important factor in the collapse of the Classic Maya states of this area. The population is estimated to have dropped by two-thirds between the mid 9th century and the mid 10th century.