The earth had a
     single supercontinent 225 million years ago.
The Great Ice
     Age accounted for the origins of the continent's human history.
By making land
     bridges, people could roam into different continents freely.
When the ice
     age finished and the glaciers melted, the sea level rose, inundating the
     land bridge stopping immigration into America for man thousands of years,
     leaving the first native Americans as the only ones.
By the time
     Europeans arrived in America in 1492, around 72 million people inhabited
     the two American continents.
They split
      into many tribes developing over 2000 separate languages, many diverse
      religions, cultures, and ways of life.
[/list]
Incans in Peru,
     Mayans in Central America, and Aztecs in Mexico shaped stunningly
     sophisticated civilizations.
Talented
      mathematicians made accurate astronomical observations.
[/list]
The Azetecs
     gave human sacrifices by cutting the hearts out of captives of battle.
Agriculture,
     especially corn, accounted for the size and sophistication of the Native
     American civilizations in Mexico and South America.  
Everywhere it
      was planted, corn transformed nomadic hunting bands into settled
      agricultural villagers.
[/list]
The cultivation
     of maize, as well as of beans and squash, reached the southeastern
     Atlantic region of North America around A.D. 1000.  These techniques were used by the Creek,
     Choctaw, and Cherokee Indians.
Unlike the
     Europeans, the Native Americans respected nature and took only what they
     needed.
Mound
     Builder and Mississippian cultures mysteriously went into decline around
     1300 
The Iroquois
     Confederation menaced Native Americans and Europeans. 
Substantial
     authority went to women of the native people of North America. 
In
     1492 less than 4 million Native Americans were left on North America. 
[/list]
Europeans were not aware that the Americas even existed. 
Europeans
     wanted certain goods brought into the continent from Asia during the
     Crusades.
     
This
      was found to be too costly 
[/list]
Marco
     Polo may have never seen China but told of the cheap treasures that lay in
     the East.
     
A
     caravel was developed to overcome strong winds and currents. 
Europeans
      could also easily be carried home from Africa from the westward breezes. 
[/list]
South
     of the Sahara Desert was a mystery to many people because it could never
     be reached until advanced sea travel came along. 
The
     Portuguese set up trading posts along the African shore. 
A
      reason why slavery became big in Africa 
[/list]
Portuguese
     went further southward of Africa in search of a water route to Asia. 
Unity occurred
     between Ferdinand of Aragon and Isabella of Castile 
Spain
     and Portugal were in a race to discover the riches of the Indies. 
[/list]