The early Neolithic human occupation of Mesopotamia is, like the previous Epipaleolithic period, confined to the foothill zones of the Taurus and Zagros Mountains and the upper reaches of the Tigris and Euphrates valleys. The Pre-Pottery Neolithic A (PPNA) period (10,000-8,700 BC) saw the introduction of agriculture, while the oldest evidence for animal domestication dates to the transition from the PPNA to the Pre-Pottery Neolithic B (PPNB, 8700-6800 BC) at the end of the 9th millennium BC. This transition has been documented at sites like Abu Hureyra and Mureybet, which continued to be occupied from the Natufian well into the PPNB. The so-far earliest monumental sculptures and circular stone buildings from Göbekli Tepe in southeastern Turkey date to the PPNA/Early PPNB and represent, according to the excavator, the communal efforts of a large community of hunter-gatherers.