I'm reading Decline and Fall of the Roman Empire now - and I'm often stuck by imagining how an author 300 years ago managed to write it. It's staggering to think how you could do so much scholarship, writing, and historical analysis without the benefits of computers, the internet, and the modern world. Not to mention the prose, which I absolutely love, and is so dense, thoughtful, and stylish.
I've also read a collection of letters from ancient Rome. Just random letters that have been translated, nobody historical or famous. The writing and thinking in the letters makes it hard to square with the Flynn Effect. The authors seem at least as intelligent, if not more so, than modern people I'm acquainted with.
Why should that not be the case? Those who can write were rich and went to school. It's not hard to imagine that they also received some sort of higher education. The difference between today and 2000 years ago is that everyone is rich by roman standards.
When you watch Clickspring's video series the biggest limitations appear to be access to raw materials and energy. There is a reason why most progress happened in the last 200-300 years. As soon as you have a lathe it is trivial to build every other machine, including the steam machine.
Which on the other hand shows how dangerous it is to have gaps on our knowledge as mankind.
People sometimes think you can't really change IQ via environment but that's because we've worked really hard to eliminate the things that can limit it.
(Plus the Flynn point is that some of the rise is about abstract sophistication rather than actual intelligence rising, people just getting better at what IQ tests test, which would be lower too.)
In a similar vein, paintings in Chauvet cave  made somewhere 32,000-35,000 years before present far exceed those made much later (such as those found in Lascaux cave, ~17,000 years BP): they used curvature of rock to generate a subtle 3D effect, in addition to being, you know, near perfect capture of the animals at the time.
There is a .. crackpot theory .. around the notion of ancient intelligence, which I entertain as it is interesting to me as a fan of Szukalski as well as various neolithic cultural introspections: Australian aborigines are the original 'wise men', who travelled across the globe and taught other tribes how to harvest the land and cultivate animals. Gabarnmung was one of their original 'universities', and Gobekli Tepi, is another.
Anyway, its a wild and not yet substantiated theory, but .. what if indeed ancient society really was a lot more advanced than we gave it credit? Certainly, many cultures overlooked in the rush to the moon, have their own deeply advanced aspects.
Not sure I would subscribe to the advanced society, so far all the artifacts we have can be explained by above-the -average achievements of an individual (rather than a group or a society, like, for example, a microprocessor). And the fact that the mankind has a pronounced tendency to punish extraordinary achievement.
* A form of cryptographic key exchange which maintained peace among the tribes for 10's of thousands of years
* A formulated "do no harm" policy for its healing practitioners that was an analog of the Hyppocratic oath, long before Europeans had the concept. They also understood the healing nature of antiseptics, and had a knowledge of infection more advanced than European medicine at the time (1700's) of first contact. (We had miasma theory: the aborigines understood that there was a smaller world that would infect a person if they didn't bathe/take care of the wounds..)
* They have the oldest surviving oral traditions in the world. We in the west cannot keep our memes alive for longer than a few months - the Australians managed to tell the same stories among themselves for 40,000+ years.
* The Australian biosphere as it stood on first contact was a result of centuries of management by the aborigines. They were maintaining the land peacefully, and harmonically, for millennia.
* The oldest mason (Stoneworking) projects in the world are found in Gabarnmung. There is evidence that this technology was exported from there to other parts of the neolithic world.
I think they were actually a lot more advanced than we give them credit. Its easy for notions of European supremacy to blind one to this, however ..
Also I wonder how many of these existed and were just lost to time by people melting them down after they broke or if this was a one off commissioned piece for someone (which seems somewhat improbable given the complexity, you'd expect there to be similar devices with less features).
I wonder why some of the technological advancements were lost due to Roman invasion, since the Romans themselves were avid engineers and has great admiration for Greek arts. I know that Roman rulers in provincial Greece were exploiting it for maximum financial gain using awful methods (at least for some time), but still... if some of these technological advancements were well known you’d think the Romans would invariably adopt and expand on them as they’ve done with so much they encountered in other civilizations.