We can only only hope that Premier Li and President Xi were being rhetorical and not scientific, because if they try to use science to explain Chinese 'blood', science is going to bite them in their bums.
Are they saying the gene associated with aggression is not in Chinese DNA ?
https://news.brown.edu/articles/2009/01/hotsauce
Association study on tardive dyskinesia and ... [Psychiatr Genet. 2013] - PubMed - NCBI
China's history is no different than that of the Europeans -- containing periods of warfare. It is irrelevant if those wars were internal to Chinese land and among Chinese. The fact of the matter is that some Chinese felt a need to violently subjugate some other Chinese for some reasons and wars resulted.
Why was there a need for all Chinese to be under one ruler any way ? What is wrong with several Chinese kingdoms or countries ? If aggression is not in the Chinese DNA, then what is the (Kung Pao) beef with Taiwan ? Why not just leave the islanders alone ?
These questions are not meant to be answered but to point out the absurdity of what these Chinese leaders said and
IF they were trying to bring science to their side, and if any Chinese members here pick up this line of belief, then you guys are truly as stupid as the argument goes.