European diseases had killed much of the native workforce.

i hope this helps ig

Explanation:

Contact between Europeans and Native Americans led to a demographic disaster of unprecedented proportions. Many of the epidemic diseases that were well established in the Old World were absent from the Americas before the arrival of Christopher Columbus in 1492. The catastrophic epidemics that accompanied the European conquest of the New World decimated the indigenous population of the Americas.

2. a land bridge connected asia and north america thousands of years ago.

4. crossing the land bridge would have been simple for the first migrants.

5. people might have crossed a land bridge while hunting animals.