Table 6 SSD and r indices of model fit for the model of demographic expansion. “Northern China” comprises the populations HJ, UR, DDS, XYH, LAN/LHS, LPS, HLS, SX and HB/BJ, and “Southern China” comprises the populations NQ, BS, LZ, CD/MK, LS/XS, SP, DQ/DR, GZ, JZS, KM, LJ and MLS