Why is Cantonese the closest to ancient Chinese?

Because Cantonese has nine tones and six tones, it is a dialect composed of Yayan (ancient Henan dialect) in the northern Central Plains and Nanyue dialect (ancient Cantonese) in Lingnan, which has many elements of ancient Chinese. Cantonese not only retains a large number of ancient Chinese vocabulary and grammar, but also retains the pronunciation and tone of ancient Chinese.

Related introduction:

The ancient Chinese in Middle Ages had Rusheng and short Rusheng pronunciation. In Mandarin, Rusheng has completely disappeared, but it is still intact in Cantonese, such as "Ten". Cantonese is a dialect close to ancient Chinese, especially middle Chinese. For example, there are many monosyllabic words, which are similar to the expressions in ancient Chinese, while there are many words with the word "zi" in Mandarin and few words ending in "zi" in Cantonese.

Extended data

Related background:

Cantonese is not the only "living fossil" of ancient Chinese, but the genes of ancient Chinese still remain in many dialects in southern China. Although the entering tone is the most complete in Cantonese, the ancient voiced sound is the most complete in Wu dialect.

Most words in Wu dialect and Min dialect are monosyllabic words similar to ancient Chinese, such as "eye", which is called "eye" in Min dialect and "station" in Wu dialect. Some ancient poems don't rhyme in Mandarin, but Wu dialect rhymes well.

Different dialects in the south record different periods just like tree rings. "Wu language carries the early pronunciation, and Cantonese carries the pronunciation of the next era. Through horizontal comparison, we can also get the historical order.

Baidu Encyclopedia-Cantonese

Baidu Encyclopedia-Ancient Chinese