What Ethnic Group Was The First To Live In America?

There are two theories that suggest from where, when and how the first men arrived in America. A study based on archeological finds in the Mexican town of Clovis that there existed a land route around 14,000 years ago between Siberia and Alaska. This theory of Clovis first suggests that these people came across this land route and populated the Americas.

An alternate theory suggests that based on remains found on Islands off Alaska and California that people may have got too America by sea from North East Asia. Since parts of California remained free of ice through much of the ice age it is possible that these early men sought shelter there.  

It is believed that around 20,000 years ago the First Nation People colonised the whole of North and South America. These first Paleo-Indians are believed to have been hunter gatherers.

What other ethnic groups arrived to America?