I wouldn't say Nords or Redguards, Imperials and Bretons are the mongrel races of the man side.
Nords are pure human and so are redguards since they were the first humans to arrive on Tamriel, but other races beat them to it obviously, was it the Beast folk that were native to Tamriel or was it the Alyieds?
Only two species survived the chaos in the beginning; one was the Hist, the other was the ancestor of Man and Mer.
The Hist eventually spawned Argonians, while the ManMer Ancestors deviated into two (perhaps three due to Redguards being of different human ancestry) groups of Man and Mer.
The Men took residence in Atmora (and possibly others splintered off and settled Yokuda) while the Mer stayed on Tamriel. The Ayleids, being Daedra worshippers, probably were the first recorded race in Tamriel (as at the time, Tamriel was still connected to Mehrunes Dagon's Plane, though barely because of Lorkhan's trickery, because Akatosh had not made his covenant with St. Alessia). Eventually the Men of Atmora came to Tamriel and by then Dwemer and Falmer had splintered off from the original Mer. Men fought with the Falmer, conquered them, then moved South into Cyrodiil where their descendants (the Nedes/Imperial ancestors) became enslaved by the Ayleids. By St. Alessia's time, Altmer and Bosmer splintered from the Ayleids (or were there before then from the Mer Ancestors, not so sure). After Alessia overthrew the Ayleids, the survivors defected into Valenwood and Summurset Isle, where they bred with the Native Bosmer and Altmer.
That is the reason the Altmer believe themselves to be so superior (They are directly connected and the most blood-related to the Ayleids, who were the first Mer descendants of the ManMer Ancestors) and why they allied themselves with the Bosmer.
During the time of the Ayleids, I believe the first Nordic people interbred with the Mer to produce Bretons, which were second-class citizens to full-blooded Mer. Orsi
mer were Elves (though not sure which kind) that were made into Orcs due to Boethiah posing as Trinimac (or in some tales devouring him, who then became Malacath as his faithful were cursed into their form or Orsimer).
I
think Boethiah (Though Azura may have done it as she taught the Chimer how to me different from the Altmer) also created the Dunmer from the Chimer, who were a group of Daedra-worshipping Mer that refused to worship the Divines, who's religion came to dominate Tamriel. Vivec is the only representation of what the Chimer may have looked like as he is Dunmer/Chimer mix (He is also the "Anticipation of Mephala").
Anyway, away from my rambling, Altmer believe all living things are subservient to them, Manmer included and would sacrifice them all in order to regain divinity.