> What is to say that the idea of knowledge being specifically given to them by a foreign culture wasn't a conscious attempt to justify their overlordship of the prior inhabitants of the land?

As far as I know, the civilizing hero myth exists in other parts of the Americas. Even if it didn't, the the civilizing HERO - not heroeS - coming with BOAT, teaching agriculture, infrastructure and civilization is way too specific to be something like that - simply because we see other things being used than such stuff when an invading people need to justify their overlordship. They mostly invoke divine beings, heavens or other holy things - not a random singular person that did good deeds.

Also, even if a singular person would be used, the tendency would be to make it into a god so that the overlordship could be justified that way. Not make it a regular person that came in quite humble circumstances, like in a boat from the sea.

Moreover, the good deeds are way too specific and mundane - teaching agriculture, infrastructure and civilization. Not divine things that could make the locals say 'Ok, since obviously the heavens gave this right to these people and their ancestors descended from the heavens, they must be justified'.

This is without the exact similarity of the myth in different regions - Osiris is another civilizing hero that came from the sea in Egypt. Apkallu also is. But most interestingly, Osiris leaves Egypt after teaching them agriculture and stuff and sails somewhere else, explicitly saying that he is going away to teach other people agriculture.

> One of the problems with archaeoastronomy is that there are too many variables

But time and dates are constant. And seen from the perspective of the architects of those monuments, you can easily see the logic that they had while building them: Since the locations of the stellar objects and their movements are invariable, there is no way anyone, anywhere, at any point in time, would not be able to know the dates which the monuments represented. Moreover, anyone would of course know or remember what major event that the monument referred to at that given point in time - like the floods during the younger dryas - because it affected everyone and it was a global event, so surely it would be remembered and transmitted from generation to generation through oral means or other traditions, right...

So, with the cultural, actually civilizational paradigm that existed then, those monuments have inviolable logic.

But of course, this also means that the info that we can reach through those monuments is limited - because we can definitely know the date of construction of those monuments, and we definitely can match those dates to a known major event like the younger dryas, and therefore concluded that these monuments across the globe referred to that event, but not much more than that. Because the rest of the information was supposed to be handed from generation to generation, wise men to wise men. We could only gleam bits of that information in the myths, legends and maybe in the local religions.

> and besides, which features are you using to establish the alignment in the first place?

If you study the matter, you will find that the placement of the features are unmistakable. Yes, there could have been a 100 years difference in estimating the exact time point. However, as far as we know, the younger dryas was a process, not a biblical cataclysm - it had a pre-cataclysm phase in which a lot of climate effects were observed, then it itself happened over a duration of time, and then it had an aftermath which took some time to settle. ~100 years would not make any difference - for the people of the time, that event would be one singular, long, ongoing catastrophe to which they would refer as 'the' catastrophe.

> I've never been impressed with the thesis that "flood myths = some cultural echo of sea level rise." The thing is that floods are a pretty common thing in... just about every climate (even deserts, which can be prone to flash floods),

Floods happen all the time everywhere. But they never happen at the same time, everywhere. For the people of the period, every known major culture, every known major population center getting destroyed by the sea would be an unparaleled thing. With no place to run to, nobody spared from the onslaught. It would be an unparaleled thing if it happened even today if you think about it.

> Arrrgh. If you ever take a class in anthropology, one of the first things you will likely learn about is the unilinear evolution model of civilization... followed very swiftly by how utterly wrong and out-of-date it is. It's not what the scientists believe

And yet, it is not what is being kept as the public paradigm. What we have is a linear progression of history modeled mainly from Christianity and its beliefs. Things happen in a linear fashion even if there were some mishaps on the way, and the civilization just progresses forward without losing everything at any point in time. There are catastrophes and setbacks, but there is no case of entire civilization going down the drain. The more advanced knowledge that is nascent in the teaching of the sciences does not seem to have propagated itself to how science is applied at the largest scale, less, how the science explains things to the public.

As said, this is just scientific conservatism that exists due to the scholastic roots of modern scientific establishment.