,000 years before Columbus to Columbus's time
Even the first American Indians were relative newcomers to their lands when compared to those who had settled the Old World; human beings have lived in the New World for less than a fifth of the time they have been settled in Asia, Europe, and Africa. Human beings have lived in Africa, Europe, and Asia for at least 200,000 years. Then, about 20,000 years ago, an ice age froze over the water between what is now Siberia and Alaska. Hunters and their families, probably following migrating herds of game, walked across this convenient ice bridge to Alaska. Because it was cold, most kept heading south.
When the ice age ended about 10,000 years ago, the Bering Straits went back to being water, and the New World was cut off from the Old. This was okay for the American Indians; the same big thaw opened passes through the mountains to the south. Roaming gradually through the wilderness that still covers much of North America, the first people reached the Tip of South America by 9,000 BCE, some 15,000 miles from the land bridge they had crossed from Siberia. That means they averaged about 1 mile of migration every 2 years.
In the year before Columbus landed, 100 million Indians probably inhabited the New World. More people lived in North and South America than in Europe. Only some of these first people whom Columbus called Indians were hunter-gatherers; most were farmers. The New World had cities before the Egyptians built the pyramids.
At the time of Columbus, the Aztec capital city Tenochtitlan (later Mexico City) was larger than any city in Europe. Unlike the dirty European cities of the 1400s, the Aztec capital had running water, clean streets, and botanical gardens. This beauty didn't lead to mellow living; as many as 5,000 human beings were sacrificed every year to please the Aztec king and his gods.