Biblical Hebrew Forum

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Chris asks:
>  So how do the analysts know
> that these four consonants were then later inserted
> to be used as vowels?

Since they are now used (quite prolifically) in Modern Hebrew to 
represent the location of certain vowels, it could be stated that 
certainly it was "later inserted to be used as vowels". Not trying to be 
an arse, just covering one end of the givens as part of explanation.
On the other end (the more ancient end), Phoenician and other Semitic 
languages started out not using matres lectionis (essentially, not 
literally, consonants used to represent the place for vowels), including 
early Hebrew. But as the first millennium BCE progressed, they became 
more prolifically used. First, they were used for dipthongs (<aw>, <ay> 
etc) and for terminal (end of word) vowels, but transitioned to also 
being used for long vowels (and occasionally where a confusion of vowels 
was desired to not exist). There was no clear-cut divide between 
not-using and using, but a long, gradual transition at different paces 
among different regions and different Semitic languages (Hebrew used it 
more broadly and quicker than Phoenician, for example).

--
Ratson Naharädama