Papuans, Melanesians, and Australian Aboriginals are not, "Blacks Outside Africa," they're different Anthropological Races, entirely, with no historical connection to Africa
As far I know, there are blacks on Oceania because they was the first human being to go out of Africa, at a time where all humans was black.
The route they take pass by south India, that's the why there is also black people in south India.
Also at the time Papua New Guinea and Australia was connect by land with Asia, so they just walk through.
Other evidence to call Oceanian's native as black can be found in ethimology.
Papua New Guinea have the "New Guinea" at in the name on reference the first black territory found by Portugueses in Africa and Guinea was a generic name to Africa and Papua received this name of New Guinea because it's innahibitants are black.
Melanesia also have a name to us remember they are black, because what make the blacks, blacks, is the melanina of the skin, and Melanesia is a derivation of the word melanina.
There is two option to explain why there is Oceania people black, maybe they can be directly linked with africans (what I believed happens in pre-historic times) or maybe it is a convergent evolution (the same who explain why Dolphins and Sharks are very similar despite have origins totally differents). I don't believe in convergent evolution to blacks on Oceania, but I also don't have evidence to desconsider this hypothesis.
Because in pre historic all humans was black, some humans start to intermix with other species of humans, as for example the europeans white who is the result of intermix with humans and neanderthais.
It seems odd to limit black people to only Negroid (African-American) people.
If "black people" are defined as "dark-skinned people," then both Negroid and Australoid should be included in the black people category.
However, Negroid is a race that evolved in Africa, whereas Australoid is a race that left Africa and then expanded throughout the world via Sundaland.
Therefore, it is scientifically incorrect to equate Negroid and Australoid as the "same black race". They are different races and have evolved differently.
However, Negroids are often treated as "a pitiful race that has suffered from racism and slavery", while Australoids are often treated as "people who just have dark skin and don't matter".
Black people in Africa are politically important; black people in Oceania are not politically important.
I guess this friend explain also very well what I think, black is a color and is associated a "dark-skinned people" as he said.
And some people of Oceania is even more black then some ethinicities of Africans, as Khoisan or Ethiopians.
And as his pointed out, Black Africans seems to be more political important then Black Oceanians.
And a game as Civilization could empoder both histories.