The human race was not originated in America. The first settlers were nomadic people from the Paleolithic era, who arrived in the continent approximately 15,000 years ago using the Beringia land bridge. This crossing was possible because the sea level had decreased abruptly after the Last Glacial Maximum. Today this piece of land has become the Bearing Strait, separating Siberia (Rusia) and Alaska (US).
You would be mostlikely to find a high population density "along the banks of <span>the Niger River," since rivers bring water, which is a crucial element of human survival. </span>
