Ultimately, this question boils down to "How are these Old Chinese syllables reconstructed to be so similar when even their Middle Chinese reflexes are quite different?"
One thing to state is that phonetic components of characters are used to help understand what these characters sounded like. As these all have 也/它 as their phonetic, there is presumed to be a phonetic closeness between them all.
Firstly, the finals, which were referred to in the earlier answer:
This is pretty spread out in the vowel space, but vowels can and do spread quite a bit through this millennium of Chinese history (詩經 to 切韻, if you will, from Zhou to Sui/Tang).
Notably, this whole family is believed to be in the same rime group in Old Chinese, that of 歌, as accounted for by the 詩經. The diphthong /aj/ makes sense as a candidate: /aj/ > /æ/ > /e/ > /i/ is super common cross-linguistically as a pathway (e.g. Latin caseus plus glide metathesis to English cheese).
The loss of final /j/ is also attested, and actually has examples from Min topolects: Fuzhounese 拖 'to pull' has two separate vernacular pronunciations, used in slightly different contexts: tăi /tʰai⁵⁵/ with final /j/, and tuà /tʰua⁵³/ without. Thus, we can account for the full spectrum of Middle Chinese finals for this family.
But each of these groupings does end up with a different reflex, and so each of these does require an explanation. Baxter & Sagart (2014) has:
- pharyngealisation of the initial as the trigger for loss of the final /j/;
- a difference in the dialect as the cause of /æ/ in some places but /e/ in others;
- a /r/ medial for those that will go on to palatalise the Middle Chinese initial;
- and 地 is just different.
Middle Chinese Final |
Chinese Characters |
Old Chinese Final (Baxter-Sagart) |
a |
他, 紽, 拖 |
*-ˤaj |
yæ |
也, 蛇 |
*-Aj |
ye |
施, 匜 |
*-aj |
je |
池, 馳 |
*-raj |
ij |
地 |
*-ˁej |
On the initials then, we have this whole phonetic series explained by some kind of lateral consonant. This is a long-standing feature of Old Chinese reconstruction, summarised by Baxter & Sagart:
In Middle Chinese, OC *l- palatalizes to y-, *lˤ- becomes d-, and both *l- and *lˤ become dr- when followed by medial/infixed *r.
Evidence from other languages is cited:
- 蜕 OC *lot > MC ywet > Mandarin yuè ‘exuviae of insects or reptiles’, Vietnamese lột ‘to skin; to throw off’
- 條 OC *lˤiw > MC dew > Mandarin tiáo ‘branch (n.), shoot (n.)’, Xiamen Min Nan 條 liâu ‘a long strip’
Old Chinese laterals are most faithfully preserved in the Wǎxiāng 瓦鄉 dialect of northwest Húnán. There, modern laterals frequently appear corresponding to OC *lˤ-, *lˤr-, and *lr-, as in the following examples from the Gǔzhàng dialect:
- 桃 OC *C.lˤaw > MC daw > Mandarin táo ‘peach’, Gǔzhàng /laɔ13/
- 田 OC *lˤiŋ > MC den > Mandarin tián ‘field; to hunt’, Gǔzhàng /lɛ13/
- 讀 OC *C.lˤok > MC duwk > Mandarin dú ‘read (v.)’, Gǔzhàng /luʔ53/
The voiceless laterals have the following:
The coronal voiceless resonants usually have coronal reflexes in Middle Chinese: *l̥- > sy; *l̥ˤ- > th. But there is good evidence for an alternative development of these initials to a fricative [x] (or perhaps [h]), which became MC x-. This development can be located in the central and western regions of the country, while the coronal reflexes [above] were probably found along the coast.
The move from lateral to non-lateral dental/alveolar stops occurs by the 1st century CE at the latest, as Sagart (1999) states:
A work with a marked spoken character, the Bai Hu Tong Yi, which records oral discussions on the classics between Eastern Han scholars in 79 CE, contains no less than five sound glosses equating OC laterals and alveolar stops.
This 白虎通義 for example has 天 (OC *l̥ˤi[n]) = 鎮 (OC *ti[n]-s), 瀆 (OC Zhengzhang *l'oːɡ) = 濁 (OC *[N-tˤ]rok).
Back to the 也/它 series then:
Middle Ch. Initial |
Characters |
OC Initial (Baxter-Sagart) |
y |
也, 匜 |
*l- |
d |
紽, 地? |
*lˁ- |
dr |
馳 |
*lr- |
sy |
施 |
*l̥- |
th |
他, 拖 |
*l̥ˤ- |
地 could be reconstructed with OC *lˁ-, like 紽, so the pharyngealisation is present in the Baxter-Sagart; the use of square brackets is:
to indicate uncertainty on the voicing specification of the initial.
We now have the odd one out, 蛇 with MC zy-. This is attributed to a prefix before the *l- lateral, as with:
- 實 *mə.li[t] > MC zyit > Mandarin shí ‘fruit; full’, pMǐn *-dž-; Proto-Tai *m.lecD ‘grain’, giving all of Thai เม็ด met, เมล็ด ma-let and เล็ด let.
But the nature of the prefix is unknown - it has to have a vowel (I presume to retain voicing into Middle Chinese). Zhengzhuang uses *ɦlj- instead.
It is true that reconstructed Old Chinese is given a phonology that can feel utterly alien to modern Chinese and indeed modern East and Southeast Asian ears. The use of these phonetic series is driven by the phonetic components of Chinese palaeography, and the search for documentary evidence of the sound changes can be particularly arcane - and yet, they are (perhaps surprisingly?) regular. At least for now, this is my understanding of the state of the art.