The above words convey "burden" Europeans had to bear.
In the poem the poet argues that the brave Europeans have to take initiative and work hard to civilize the uncivilized people. He regard the same as burden for them as they have to serve others and don't receive any thing in return. The burden for them is being conveyed through words like exile, harness and bind. In nutshell, the poet justifies the colonialism through this Whitman's Burden theory.
Over the period of the Atlantic Slave Trade, from approximately 1526 to 1867, some 12.5 million slaves were shipped from Africa, and 10.7 million arrived in the Americas.
