From the paper:
It is likely that MBWs was an admixture of East Asians. First, this 19-individual population was surprisingly more diverse than any of the 32 populations. In parallel, PC plot (Figure 2) of estimated percentage of shared hgs strongly supported that MBWs was obviously distinct from all 32 compared populations on first and second principal component.It would be interesting to verify that the ancient Chinese populations from different localities had low diversity as well. I am reminded of recent studies on ancient Danish mtDNA, which found haplogroups in the ancient populations that are rare nowadays and seem to point to individuals of foreign origin. Have mtDNA gene pools grown more diverse (due to migration) or less diverse (due to selection?) since antiquity?
PLoS ONE doi: 10.1371/journal.pone.0003275
Mitochondrial DNA Evidence for a Diversified Origin of Workers Building Mausoleum for First Emperor of China
Zhi Xu et al.
Variant studies on ancient DNA have attempted to reveal individual origin. Here, based on cloning sequencing and polymerase chain reaction-restriction fragment length polymorphisms, we analyzed polymorphisms in the first hypervariable region and coding regions of mitochondrial DNA of 19 human bone remains which were excavated from a tomb near the Terra Cotta Warriors and dated some 2,200 years before present. With the aim of shedding light on origins of these samples who were supposed to be workers building the mausoleum for the First Emperor of China, we compared them with 2,164 mtDNA profiles from 32 contemporary Chinese populations at both population and individual levels. Our results showed that mausoleum-building workers may be derived from very diverse sources of origin.