Fossils on one continent may be similar to fossils of another continent this observation supports which theory

Continental Drift theory- the theory that the continents used to be one land mass that slowly drifted apart into separate pieces. The supercontinent is called Pangea. It supports this theory because it explains why fossils like the Mososaurus, a fresh-water reptile, fossils are found only on the eastern part of South America and the west coast of Africa. There is no other way that they could be there as the distance would be too great to swim if the continents were in the same position they are today.

Nation of conflicting ethnic groups

I'm pretty sure it's c. extremely gradual but not 100% sure though.