Recent Black immigrants from Africa do much better than native Blacks.
That could still be cultural. None of the Africans I know (immigrants to Europe) have a culture that even vaguely resembles that of African-Americans.
The natives are descended from generations of slavery in which the smartest ones were killed by the masters as the smartest ones would rebel.
I just have to comment on this, because you're saying:
- rebellious slaves would disproportionally be the "smart " ones
- slavers would kill rebellious slaves
- as a result, only less "smart" slaves would procreate
- current-day African-Americans are the descendants of these less "smart" slaves
- therefore, we should expect modern blacks in the U.S. to be of lower intelligence than other "races"
- this explains the lower rates of academic success and affluence among American blacks
This is the genetic "black inferiority" argument, which is just the opposite side of the "white supremacy" coin.
But several of the assertions above are not correct; for one thing, rebelliousness does not correlate positively (or even at all) with intelligence. In fact, one could reasonably argue that the intelligent slave would be more likely to know how to keep his head down and play the system to the extent it was possible.
Another point is that slavers did not indiscriminately kill slaves that stepped out of line. Instead, they would typically administer horrible punishments that would both inflict pain and serve as a deterrence. This makes sense, as each slave represented a major investment for the slave owner.
Sure, in some instances a slave would be killed if the transgression was seen as sufficiently egregious; the typical case would be sexual assault (against a white woman), having an interracial relationship, or engaging in abolitionist advocacy.
Immigrants are self selected risk takers which is why they are more successful than any native group.
This argument seems logical, but statistics show huge differences between the various immigrant groups. While some immigrant groups (like the Chinese and the Indians) are hugely successful in both the US and in Europe, others (like the Somali and Bangladeshi) are mostly unemployed and collecting benefits. Again, culture seems to play a huge role.