Board Thread:Lore Discussion/@comment-24.44.141.89-20131113224543/@comment-4373298-20140318162605

So it has been mentioned that the they are the Argonians. This makes a lot of sense, as both the argonians and Khajiit are known to have been in Tamriel long before mer and men. The Ka-Po-tun as described sound exactly like Khajiit, and the reptilian but humanoid descriptions of the Tsaesci resemble Argonians.

I think the best near proof! of this is in 2920 however. Reman is speaking with the potenate about his plans to subdue the uprising in Black Marsh. He makes a remark to the effect that the Argonians are brutish sub-person beasts, but immediately apologizes to the potenate and assures him that he does not consider the civilized from Akavir amongst that number. To me, seems pretty clear that the Tsaesci are Argonians. It also says that the Potenates son was humanoid, scaled, and had a tale, like an Argonian, but fought in the gear and manner of the Akaviri warriors.

It is said that the Tsaesci "consumed" the men of Akavir. If they are humanoid like Argonians, and it is said that they interbred with the noble families or Cyrodiil, it may mean that the men of Akavir became assimilated into the Tscaesci through interbreeding and marriage.