A SWARM OF DRAGONS TWO
THE GREAT NORTH SOUTH DIVIDE
THREE MAPS TO CONSIDER
Note Some People would map two or three sub-divisions of Mandarin.
Observe also the greater linguistic diversity south of the Yangtze.
If this map included NON SinoTibetan or SinoTibetan languages that are NOT Sinitic there would be even more colors!
Now a topographic chart.
Looks to me like Archaic Chinese split off from ProtoTibetan some where in NW China probably the WEi river valley with "Mandarin" spreading first eastwards along the Yellow River and then SW and S later however the lakes hills and mountains of Southern China slowed its expansion enough for some diversity to endure.
This map doesnt include Chu or Yue or reflect the larger size of the major lakes in the past but note that border between WEI and WU and the rivers.
Now scroll back up to the top map.
HAN culture seems to have spread along rivers rather than roads and there's a distinct North South Divide that abides throughout the centuries and I will provide more maps to show this.