^interesting post. But modern DNA research does not seem to confirm the melting pot theory as far as I remember. Highlanders have minimal amounts of recent Semitic admixture. The rest of the West Eurasian admixture is pre-agricultural and is shared with other groups of the Horn. How do you explain this? Is there any concrete evidence of a large scale population movement from the countries that you mentioned into Ethiopia? For all modern day habeshas to descend from Axumites, this would require a large population movement.
And what do you make of the fact that there is an Agaw substratum in both Amhara and Tigrinya? This would suggest that the dominant language in the Ethiopian Highlands was Agaw until it was replaced by Semitic.
IMO the ruling class might've been of mixed heritage, but most of the subjects were Cushytes who simply adopted a Semitic language over time. "Habesha" is just a culture really. Lots of assimilated people became habesha whereas others lost their "habesha privilege" and got their habesha card revoked the moment they adopted a different culture/religion (I.e the Muslim Semitic speakers of the Horn).
lol, I'm sure I'll need to edit this a lot but I'm trying to reply before I go to work.
The melting pot moreso explains the extreme variance between Habeshas, plus the mixture was not exclusively Semitic by any stretch but it had Semitic elements within it such as the language and script of Ge'ez. I didn't mean to suggest that it was a mass migration but rather a gradual one upon hundreds of years which was stimulated by Axum's central role in international commerce and later due to invaders/travellers at various points in Ethiopian history. Axum/Ethiopia's reputation at the time is why many peoples came to it's shores. As I stated in the previous post, the Beta Israelites migrated all the way to Ethiopia and became a part of the society and later lived in the Simien Mountains. Bilal the Ethiopian advised Prophet Muhammad to send the first hijra to Ethiopia where they would be protected by the Axumite Emperor of the time Negus Armah. So again, when you factor the long history of Ethiopia as a sanctuary along with having been an economic power it brought many people to its shores which affected the indigenous population. Hell, Christianity found it's way to Ethiopia through a shipwrecked Syrian and even when the royal court converted it wasn't from Judaism but rather from Ethiopic cosmology. Axumite nobility worshipped the sun, moon, and stars. If you look at the obelisks, it has been argued that the design of the top of the obelisks is a representation of the rising sun which speaks to this ancient cosmology. So Jewish influence on Habesha cultural development varies. I'll be honest though, Ethiopia is probably still 90% unexcavated so there's a great deal still unknown about Axum and Ancient Ethiopia. At the very least, the British could stop being jerks and hand back all the artifacts that were stolen from the country in the 19th century.
So some Habeshas have more "mixed" features while others more closely resemble their Cushiitic foundation. These mixtures could be very old or more recent like the Portuguese, Arabs, Turks, Italians, etc. To be clear, the population movement in and out of the region wasn't large scale however compared to other parts of Africa it was a bit more pronounced. From the little information so far uncovered, the history speaks about the capital being a hub for the African side of the global market and through this there were different groups of people (mostly merchants) whom came to Ethiopia/Somalia/Djibouti/Eritrea and settled. I won't speak on pre-agricultural admixtures, but don't forget that the Axumite Empire at different points in time controlled the coast from modern Eritrea to the port city of Zeila in Somalia. When Yemeni Christians were being persecuted by the Jewish Yemeni kingdom, Axum invaded and took administrative control of what is now Yemen which inspired more migration. Some historians have suggested that the Ethiopian Jewish population grew from this event by the migration of a small group of Yemeni Jews into Ethiopia. There is also a population of Ethiopians in Yemen from the time of that Axumite occupation whom still exist today, I believe they are known as the "Dakkas".
So clearly being a hub for African wares like animal skins, gold, incense(very important), and ivory, turned Axum into a magnet for merchants from around the Ancient world looking for their fortune and this also sent Axumite traders all over the ancient world. Archeologists have found coins from Axum from as far as in the waters off the coast of Gujarat in India so this shows how powerful and expansive of a trading nation Axum was. So of course in the Ancient world you couldn't have a mass scale migration, but the gradual migrations from different parts of the world definitely played a role which would explain why there was never a spike in mixture because the indigenous population always outnumbered the migrant groups which also preserved our overall Africanness and didn't dilute us like the North Africans for example. When you factor the long period of time between Axum's rise and fall it definitely can be said that it's position in the Ancient world played a critical role in the development of the people known as Habeshas.
As I said, Agaws are a common thread because they were the original inhabitants of the highlands. And yes, Agaw was the original language of the highlanders, but again, Ge'ez came before Amharic/Tigrinya/Tigre so people were speaking a Semitic language for centuries before the creation of those exclusive vernaculars. Part of the stigmas around the Jews was because it was believed that they preserved the Agaws art of sorcery/witchcraft which was anti-Christian they were undesirables. Agaws being on the periphery helped save their language and culture from extinction but the people that would later become Habeshas were already Semitic speakers by the time Axum fell. I agree that Agaw was probably still widely spoken but since they weren't the administrators of the empire they had to adopt the Semitic language as you said. My only disagreement is in when that transition took place which was to me during Axum's reign as opposed to after it's reign. Ge'ez probably spread because Axum was according to scholars, a collection of small kingdoms/fiefdoms which was administered from the capital as a grand empire. This, as well as the church, would explain why the Semitic Ge'ez language was able to better travel through Ethiopia before the fall of the Empire.
Your last point is true though, Habesha was almost like a "quasi-Jew" where ethnicity and religion blended together. Habeshas that were Muslim were known as "Jeberti" which is the root for the modern name "Djibouti". But ethnicity still played a role, remember Ethiopia was a slave society and practiced a caste system of sorts so although a slave from Sidama could learn Amharic/Tigrinya or practice the customs, to a Habesha that slave is assimilated and not a pure member of their tribe(Amhara/Tigray). It's only through time that this is forgotten and future generations are fully assimilated into the Habesha bubble. This denial of true assimilation in the past is also one of the reasons why there's so many racist undertones in Ethiopian culture today. As close as the Jews and Amharas lived they couldn't be further apart. Modern times is when this has been relaxed much more I would definitely agree with you that now the nature of "Habesha" is more cultural/ethnic than it is religious.
One more point to make is that the very Jewishness of the Beta Israel is not 100% agreed upon. Some scholars believe that during the reign of Susenyos when he abolished the Orthodox Church in favor of the Catholic church, a sect of ultra-Orthodox Christians split and converted to Judaism in protest and had their lands taken as a result. Orthodox Christians believe they were the people that came with Menelik bearing the Ark which the Beta Israel wholly deny, and the Beta Israel themselves argue that they are the lost tribe of Dan. So there's no 100% consensus. Of course, as long as Jewish scholars affirm their Jewish character it doesn't matter. Now I don't agree with the theories that argue against them being Jews but it shows how like many things in Ethiopia, the story is shrouded in a lot of mystery.
Here's some light reading:
Aksum | ancient kingdom, Africa
Khan Academy
http://www.newworldencyclopedia.org/entry/Aksumite_Empire
Here's a pic of the trade routes through Axum according to Ancient Greek scholars:
Mind you, trade with India goes back much further than Axum. You'll notice it in how similar our foods are for example like tea (Shye=Chai) (Channa Dal=Alecha Kik wot). Some Amharic words like the word for earrings "guticha" is believed by some scholars to have Indian origins. I'd argue that one of the similarities that Habeshas have with people from northern Somalia and Djibouti is our contact with India. I'll add more when I get a chance, I might have some books to cite but I have to go through them after work.