Board Thread:Lore Discussion/@comment-75.72.62.174-20160217000807/@comment-26145872-20160228214533

To answer your question, it's likely that many Imperial citizens as of today posess Atmoran ancestry, though this would have required breeding between the Nedic and Atmoran races. Additionally, it is confirmed that most modern-day Imperials are indeed descended from the native Nedic humans that lived on Tamriel in ancient times as well as the Atmorans who returned to Tamriel during a point in the Merethic Era known as The Return and settling across Tamriel.

To answer your second question concerning the Breton race, it is known that the Bretons are, on their Elven side, descended from both Aldmeri members of Clan Direnni, as well as Ayleid exiles who traveled to High Rock from Cyrodiil. As for their Human blood, it was both a mix of ancient Nedes and Atmorans who migrated from their home continent of Atmora after The Return.

Additionally, it was not the Atmorans who were enslaved by the Alyeids. That was the Nedic Humans in the Merethic and First Era. The Atmorans, after The Return, decided to help free the Nedic slaves of Cyrodiil from their own Elven masters after the Atmorans had done the same in Skyrim. Nedic Humans in ancient time stumbled upon High Rock and were quickly absorbed by Elven culture, and after The Return, a number of Atmoran settlers traveled to High Rock as well as other provinces aside from Skyrim.