Which country played the biggest role at the beginning of the Atlantic slave trade?

Portugal

The most active European nation in the trans-Atlantic slave trade was Portugal, which used the forced labor of Africans in their Latin American colonies in present-day Brazil. Almost 3.9 million enslaved Africans were forced to embark on Portuguese ships.

Explanation:

1. between 1754 and 1763

2. a land bridge between siberia and alaska that was exposed during the most recent ice age when the waters of the bering strait receded.

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these civilizations were located around fertile rivers, where they could produce an abundance of crops