In "the negro speaks of rivers" what does the poet imply about the durability or dignity of his people when he refers to the great age of rivers.

"The Negro Speaks of Rivers" was written by "Langston Hughes" (1902-1967) when he was only 18.

The poet implies that black people's souls are as wise and deep as old rivers. As old rivers have seen centuries of World's history so has the black race.

Explanation:

By comparing and linking black people with old rivers which are the lifeblood of civilizations such as Euphrates, Congo and Nile, Langston Hughes implies that black race has in its roots the richness of history, the wisdom of ancient ages. As rivers are eternal and have stood the tests of time so has the black race stood firm in spite of all the hardships near River Nile (building Pyramids) or near Mississippi (New Orleans slave markets).

i believe it is the first choice (1.)

because the major theme is(“both the wild and civilization have rules.”)

and also as u said,( based on what buck learns within the call of the wild, "both the wild and civilization have rules".this is true of humans within society as well.