The answer is that federal troops we're withdrawn from the south.
The Olmec is influences continued to appear in many later Mesoamerican civilizations. Cities of the Aztecs, Mayas, and Incas were as large and organized as the largest in the Old World, with an estimated population of 200,000 to 350,000 in Tenochtitlan, the capital of the Aztec empire.
The correct answer is opposable thumbs. Humans have opposable thumbs which allows them to easily grip and pick up objects.
The novel Uncle Tom's Cabin exposed northerners to the evils of slavery.
The Sumerians, Babylonians, and Assyrians all had their beginnings in the area now known as Mesopotamia.