The Negroid thing is more speculative, due to the lack of decent human remains with that age, but we DO have some old remains (older than 10.000) that are seemly negroid, for example the skull nicknamed "Luzia" that was found in Brazil. (there are some others too, but Luzia made international news when it was found).

Some people are trying to find more remains, and others are trying to do genetic research on those remains, one theory is that there was two (or more) waves of migration.

Another theory, is that the people that crossed the strait 22000 years ago were negroids, and "co-evolved" to have Asian features like modern Asians because of converging evolution or coincidence.

A third theory that was more popular when there was fewer evidence (when Luzia was first found) was that Luzia features were just normal genetic variation, and that she was a mongoloid that looked negroid because of randomness.