I realized that it is possible that mandarin has evolved greatly from Middle Chinese, ever since the Yuan Dynasty(ethnic Mongols) came to power. Middle Chinese is the Chinese spoken during Tang, Sui and Song dynasty where both Cantonese dialects and Hakka still preserve many features of Middle Chinese. As the Mongols speak a altaic language and probably Chinese was hard for them to pronounce[ the initial consonant (Ng-), some vowels, Final consonants (-t,-m,-k,-p)], the new foreign rulers of the Middle Kingdom probably changed Middle Chinese to what we know as Mandarin, inorder for the rulers and other Mongols to be able to learn & speak Chinese easily.
Example of Initial consonants:
Me; Ngo -> Wo [the initial consonant Ng- was probably hard to pronounce, so they changed it to a "W"]
Person; Nyin or Ngin -> Ren [the evolution was probably from Nyin -> Yin -> Yen -> Ren]
Example of Vowels:
I guess some of words that contained the "i" vowel were hard to pronounce so they changed some of the words to "ei", since in Mandarin they sometimes use "i" or "ei" in their words; where as in Middle Chinese the "i" vowel was probably only used.
United States; Mi Guok -> Mei Guo [Mi was probably hard for them to pronounce, so they changed it to Mei]
Example of Final Consonants:
Yit -> Yi [the final consonant -t was probably removed because it was not easy to pronounce]
Sam -> San [ditto with -m]
Liuk -> Liu [ditto with -k]
Ship -> Shi [ditto with -p]
