The Olmec civilization was the first known Mesoamerican civilization, located in southern Mexico between 1200 BC to 400 BC. They built large religious structures and stone monuments, created colossal stone heads to represent rulers, and had a religion that centered around a jaguar rain god. While the exact cause of their decline is unknown, the Olmec influenced later Mesoamerican cultures like the Maya and Aztec and were pioneers in government, arts, and science in Mesoamerica.