How common was this skill? Seems like it could have been limited to people with savant-like memorization skills. Certainly memorizing all of Homer is more useful that memorizing pi to a gazillion places.
Many Muslims still memorize the Koran, about 70,000 words
There are even apps that help practice.
Memorizing the whole of the Koran is still a fairly commonplace achievement in the Islamic world.
Or so I am given to understand.
It’s not unheard of for someone to memorize the Bible, either, and that’s over 780,000 words. It’s mostly prose, too, which makes it harder than poetry.
Brittanica says Greek Fire was petroleum-based, but its exact composition and manufacture are lost:
Again, though, that’s a “many methods” problem. We still today have weapons consisting of petroleum products squirted out of a nozzle and ignited. I imagine that we even have several different designs and compositions of such. We don’t still use the ancient Greek recipe, but that’s just because our modern recipes are even better (for values of “better” that include the enemy dying in screaming, burning agony).
The Incas had strains of Maize that grew at much higher altitude than modern crops will allow. They were lost during the conquest (when Inca culture was wiped out and the Spanish forced the indigenous populations into European style farming)
I would say no…there is nothing that earlier humans could do that we simply can’t today. We might do it differently, and exact techniques have of course been lost (many metallurgical ones I can think of off the top of my head), but we have the skill to simply do it differently to achieve basically the same results. In every case I can think of, humans can still do basically the same skills as our forebearers could, heck even down to trying to recreate the exact techniques used for things like flint knapping or using a dolerite hammer to shape stone, even while there is no practical reason to do those things in those ways anymore, but just because folks love to learn stuff like this.
I suppose it’s possible that in the future this could happen, where humans lose the skills necessary for, say, rocketry and orbital flight or some of the advanced stuff we have today, but to date, I don’t think there is anything like that.
People are criss-crossing skill and product.
Greek Fire is a product, Roman cement is a product, silphium is product etc. What the OP was looking for is a particular skillset.
There’s an ornate form of masonry called Polychrome that was developed by James Earley in the 1930s and 40s. Five or six houses he built are still on proud display in Silver Spring, MD. (He was angling for a war-era construction contract in the DC suburbs, one that ultimately went to somebody else.) He died and his laboratory burned down, destroying his notes. His procedures have not been duplicated successfully.