Original sentence: It is disputed "chicken or egg" question if the influential Arabian was either the ancestor of the breed or was developed out of this breed.Some historians believe that the two are different strains of the same breed.The Akhal-Teke has had influence on many breeds, including the Thoroughbred through the Byerley Turk (which may have been Akhal-Teke), one of the foundation stallions of the breed
Edited sentence: Some historians believe that the two are different strains of the same breed, and that the incredibly influential Arabian was developed out of this breed.The Akhal-Teke has had influence on many breeds, including the Thoroughbred through the Byerley Turk (which is thought to be Akhal-Teke), one of the foundation stallions of the breed