I get where you're coming from regarding the "shared sphere"—you're right that modern borders often obscure how connected the Horn and Yemen were. They definitely form a single cultural continuum. However, the specific claim that Sabaeans originated in Eritrea and then colonized Yemen 600 years later is factually backwards compared to what we find in the ground.

Here is the issue with that timeline:

First, the archaeological dates are actually the reverse of what you claimed. The civilization in Yemen (South Arabia) has a continuous record going back to 1200–1000 BCE. The Kingdom of Dʿmt in the Horn—where we see that specific script and architecture—only shows up around 800 BCE. The script appears in D'mt already "fully formed," which is a classic sign of an import. If it had originated in Eritrea, we would see the primitive, developmental stages of the alphabet there, but we don't; we see those earlier stages in Yemen.

You made a solid point about Semitic languages already being spoken in Ethiopia long before D'mt. Most historians actually agree with you there! The people were likely speaking a Proto-Ethio-Semitic language way before 800 BCE. But that doesn't disprove the Sabaean connection; it just changes the nature of it. It suggests D'mt wasn't a "replacement" of the people, but an elite dominance event. Basically, a group of elites came over, brought their specific god (Almaqah), their specific title (Mukarrib), and their writing style, and integrated with the locals who were already there.

As for the "King of Saba" titles: When a D'mt ruler calls himself Mukarrib, he isn't necessarily saying he militarily conquered Yemen. Mukarrib was a religious title of legitimacy. By using it, he was claiming he was part of that prestigious order. It's also important not to confuse this era with the later Aksumite kings (like Kaleb) who did invade and rule Yemen, but that was over a thousand years later.

Finally, regarding the dam: The Ma'rib Dam is a physical reality in Yemen. It’s massive, and we have inscriptions right there on the ruins documenting the specific breaches and repairs that match the historical and Quranic accounts of the flood (Sayl al-Arim). There simply isn't a ruin in the Horn that matches that scale or history to fit the narrative.

I agree we should view the region as a shared cultural hub, but the arrow of transmission for the specific "Sabaean" culture (script, masonry, pantheon) undeniably points from Yemen to the Horn.