the English “G”. Their closest equivalent

[GoodTaste]

Should "." be "," here? Because "their closest equivalent" refers to "G."

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At that time, the Greek gamma wasn't necessarily written in the modern Greek way (Γ). It was tilted over, looking more like our modern “less than” symbol (<). It could also be written in a curved form (C). It so happened, however, that the Etruscan language did not include a sound corresponding to the English “G”. Their closest equivalent corresponded to our English sound “K”. So they used the gamma as the written equivalent of their “K” sound. The fact that the Greeks already had a symbol for the “K” sound somehow got lost along the way. To the Etruscans gamma and kappa would have sounded the same (should we call those camma and cappa?), so the kappa could be discarded.

Source

 

[Raymott]

So you want to say:
'It so happened, however, that the Etruscan language did not include a sound corresponding to the English “G”, their closest equivalent corresponded to our English sound “K”.'

That's not grammatical; it introduces a comma splice. You could put a semicolon there. It would also be correct with a comma if "corresponded" was changed to "corresponding".