I've done a bit of searching but I've not found a thread that really tackles this issue. So, I'm aware that in some (or all?) North-West Semitic languages there is a merger between /ʕ/ and /ɣ/ and between /ħ/ and /x/, but my knowledge of this phenomenon is very incomplete. I have some questions: Is this merger common amongst all NW Semitic languages or only amongst some? When did it occur in those various languages? Assumedly Phoenician had this merger since before they developed their alphabet, since they have only one letter for each pair. Is it safe to assume that a language/dialect that realised one as a velar fricative also realised the other as velar, and the same for pharyngeal? Is there any evidence for a language which had one pharyngeal and one velar fricative? I'd also be very grateful to people for directing me to some academic literature. Thanks.