So humans migrated from Atmora, to Tamriel, and the Imperial/Redguard races were born? Only until Ysgramor landed in Skyrim the Nords were born? And human-elf hybrids are the Bretons?

And Orsimer, High Elves, Dark Elves, and Wood Elves all trace their lineage to the same ancestors?

And Argonians are led by the Hist, who once inhabited all of Tamriel?

Imperials are natives to Tamriel.

The Aldmer migrated from a continent called Aldmeris.

Don't know that much on the Hist so I can't comment on that.

http://www.uesp.net/wiki/Lore:Races