When exactly did the existing Cantonese hybridize?
First of all, Cantonese is definitely not the ancient Chinese from the time of Confucius. Just compare it with any Middle Chinese pronunciation video, and you’ll see that the phonetic structures are almost entirely different.
Secondly, it’s also unlikely to be from the Sui and Tang dynasties. If Cantonese had been passed down from the Sui and Tang periods, there should be N types of Cantonese dialects in Guangdong today, similar to the situation in Hunan and Fujian, where dialects vary every three miles. The uniformity of Cantonese across the region suggests that its formation period couldn’t have been too long. Most of Guangdong, apart from the Pearl River Delta, is made up of secluded mountainous areas. In an agrarian environment, where generations have lived in the same place, the language couldn’t have changed significantly (without the migration of people speaking other dialects). However, due to continuous wars, residents moved around, and dialects hybridized. It’s easy for the language on either side of the same mountain to change due to the migration of people from different regions. But this phenomenon is not prominent in Guangdong; people in the Pearl River Delta can generally understand the dialects of western and northern Guangdong. This indicates that the existing Cantonese likely formed during the last large-scale population migration, which was during the Yuan and Ming periods.
Additionally, from the perspective of surname migration, it’s hard to say that Cantonese has been passed down from the Sui and Tang dynasties. For example, the Chen surname, which makes up 10% of Guangdong’s population, only migrated here at the end of the Southern Song Dynasty; the Liang surname, accounting for 5% of Guangdong’s population, migrated during the Northern Song Dynasty (both less than a thousand years ago). The major surnames in Guangdong mostly formed when prestigious families from the Central Plains fled here during the Song and Yuan periods. As a group with relatively high social status, they moved here with their entire families and became major surnames. Therefore, the Central Plains pronunciation from the Song and Yuan periods would have been largely preserved in later Cantonese.
Another point is the well-known “Huguang fills Sichuan” event over 300 years ago. After the Eight Princes’ siege of Sichuan, the population of Sichuan was reduced to less than 100,000, and a large number of people were relocated from Hunan, Guangdong, and other places to Sichuan. Hakka and Cantonese dialects were completely preserved in Sichuan. However, today, Hakka people in Sichuan and Meizhou can hardly communicate with each other in Hakka, as the two Hakka dialects have diverged significantly (the Hakka dialect in Sichuan has changed greatly under the influence of local dialects in just 300 years).