Thanks for your post.
One of the most interesting facts I have learned from drawing up my genealogical tree is that I have 8 g-grandparents, 16 gg, 32 ggg, 64 gggg, 128 ggggg, 256, 512, 1028,etc. So, I really have very little connection to any single ancestor of 10 generations removed.

Most of the people in England can trace their ancestry to the illegitimate children of the kings of England--80% just from King Edward III.

Therefore, if a few people of non-African origin really did come to the U.S. in 1492 and mix with the slave population, it would not have changed the culture or DNA make-up of slaves to much degree.

And we know from the colonial to early national period records that there were no separate non-African slave communities. For example, when members of the Coleman family of Dinwiddie County, Virginia, won their freedom based on descent from an Indian (Native American) woman brought as a slave to Virginia about 1705, their descendants registered as free Negroes in Petersburg in 1800: "dark Brown Free Negro or Indian, short bushy hair."
Paul