There are many characters that have the initial "m-" and contain "少" as a phonetic element at the same time, such as 妙, 秒, 眇, 竗, etc. I thought this was a good reason to judge that "少" used to have "m"(either voiced or voiceless) in Old Chinese. Then I looked up through B-S's reconstruction. They reconstructed it as /*[s.t]ewʔ/, but I couldn't find any explanation. What is a good reason to judge that "少" used to have "t" instead of "m"?
Baxter–Sagart's (2014:135) view on *s.t-:
Preinitial *s- had a range of effects on unaspirated stops and affricates . . . Old Chinese *s.t-, but not *s.tʕ-, evolves to MC sy- (plausibly [ɕ]), presumably through an intermediate stage [stɕ] that simplified to the Middle Chinese palatal fricative sy- under the influence of pre-initial *s: *s.t- > *stɕ- > *ɕ- = sy-.
少, B–S's MC reconstruction is syewX. The consensus of MC is ɕiᴇuX. This is supported by the fanqie
書沼切of the third division in Guangyun. All MC reconstructors concur the 書-initial is /ɕ/.
I believe B–S is aware of the conflict between the above theory and the presence of the
妙-type phono-semantic compounds. In fact, B–S applied the square brackets (which indicates uncertain identity, not lack of evidence, in which case parentheses would be used) to not only *s.t for
少, but also *m for the
妙-type phono-semantic compounds:
Zhengzhang circumvented the backward MC-to-OC theory in the first point and directly reconstructed
少as *hmjewʔ in OC.
Reconstruction evidence from the Chinese script is important but needs to be used with caution (Baxter–Sagart, 2014:26):
As with rhymes, in using evidence from the script to reconstruct Old Chinese, it is important to take into account not only which words were written with the same phonetic element, but also which words were not written with the same phonetic element. Traditional Chinese philologists noticed cases where initial consonants that were very different in later pronunciation were apparently treated as interchangeable in the early script.
The example 喻四古歸定 was immediately given where initials y- and d- in MC were often interchanged in OC:
弋 yì < yik ‘shoot arrow with string attached’ is phonetic in
代 dài < dojH ‘replace’
余 yú < yo ‘I’ is phonetic in
涂 tú < du ‘path’
Baxter, William H., and Sagart, Laurent. Old Chinese: A New Reconstruction. Oxford University Press, 2014.
I'm not a linguist, but the phonetic element should have some validity, some characters used as indicator of phonetic in a compound character. Only that you listed a limited amount of letters and got the conclusion. The phonetic 少 indicates pronunciation of 'ao' instead of 'm', the letters you listed read 'miao', though different intonations. Indeed 少 itself is pronounced 'shao' instead of 'm+vowel'. But some ancient Chinese pronunciation of the same letter was different from today, so I think we should refer to work of Chinese archaeologists, historians, linguist and literature scholars. Hope that helps ;)