With more studies on Sino-Tibetan languages, the hypothesis of Sino-Tibetan including Sinitic, Tibeto-Burman, Kam-Tai, and Miao-Yao has been challenged. However, the genetic relationship between Sinitic and Tibeto-Burman has been generally taken for granted until now. If looking into the evidence for such genetic relationship, there are still two remaining problems:

1, more than several hundreds of correspondingmorphemes between Chinese and Tibetan are listed up to this date. How can we make sure they are not accidentally corresponding?

2, for those which are not accidental correspondences, how can we make sure they are cognates instead of loanwords? Loanwords can also result insound correspondence as we see between Old Chinese and Tai, Japanese, Korean, Vietnamese. Correspondingmorphemes are a necessary condition of genetic relationship of languages, not a sufficient condition.

Recently, based on more rigorous methods, we have compared Old Chinese (OC) with Written Tibetan (WT) and Proto-Yi (PY) based on Yi dialects in Sichuan and Yunnan, more evidences have been accumulatedfor the genetic relationship between Sinitic and Tibeto-Burman.

In order to eliminate accidental correspondences, we propose a correlated principle to build correspondences. For example, it is necessary to find out both vowel correspondence and ending correspondence if we claimthe sound correspondence for afinal. 

Rank distributions are largely tested in our fieldworkand the result is clear. In languages with genetic relationship, the ratio of cognates in 1st 100 words (high rank kernel words) is higher than that in 2nd 100 words (low rank kernel words).In languages with contact relationship, the ratio of loanwords in 1st 100 words is lower than that in 2nd 100 words.

According to our correlated principle, 150 correspondingmorphemes between Old Chinese and TB are found out, 40 of which belonging to kernel words with the following distribution:

The first 100 words: 26

The second 100 words: 14

This distribution strongly suggests that Chinese and Tibetan have genetic relationship.

We have also compared Old Chinese and Proto-Yi and found out the following rank distribution of kernel words:

 The first 100 words: 21

The second 100 words: 6

This result also suggests strongly that Chinese and Yi have genetic relationship.

In conclusion, the rank distribution of kernel words supports the genetic relationship between Sinitic and Tibeto-Burman.