Long winded You're Welcome follows -

Alternative history is a fascinating topic. It raises lots of questions that make institutions uncomfortable. Start digging and you immediately run into Graham Hancock who is just about universally pilloried by academia as a kook and he may well be. However, he has dug into some fascinating stuff, specifically the Paracas skulls -

http://www.latinamericanstudies.org/paracas-skulls.htm

Academia says they are like that from binding and indeed there is evidence of binding in past Latin American cultures. He posits that the ones binding their skulls were perhaps emulating the human offshoots with elongated ones. Looking further, the elongated skulls are missing front-to-back sutures found in our skulls (big genetic difference between "normal" humans). Further there is a DNA link between these skulls and ones found in ancient tombs in the Black Sea area, 10,000 miles away. So the bottom line is that these skulls are organically different (sutures & vertebrae position going skull). Artificial means to reshape the skull could not account for that. This is based on what you can observe directly on the skulls extant. Putting them through DNA testing and finding that there are phenotypes associated with Eastern Europe that are found nowhere is South America is another big data point. Added together it should at least spur more investigation as to who these people actually were rather than academia waving hands and saying "bound skulls".

Two youtube channels (UnchartedX and Bright Insight) tear into more such as Egyptian tech, the green Sahara, and many other things. They don't get into spiritual, paranormal, or space alien aspects and just go by what has been found that does not make sense when textbook dogma applied. UnchartedX takes great pains to go by engineering details left on artifacts balanced against tools that have been found. The equation does not balance out in that you cannot recreate many artifacts the Egyptians left with the tools we know about. Therefore, they must have had tools/techniques we don't know about. Seems like a fair point. What all these guys show is how aligned published academia is against their questioning. The establishment will not consider theories that would crash their own. The point they all seem to be converging on is that 10-12000 years ago there was a catastrophic climate event, an instant ice age called the Younger Dryas. Did that reshape the planet, crash global spanning civilization(s), and wipe entire cultures out? This may have been from an asteroid hit which darkened the sun for years.

https://upload.wikimedia.org/wikipedia/commons/6/63/Evolution_of_temperature_in_the_Post-Glacial_period_according_to_Greenland_ice_cores_%28Younger_Dryas%29.jpg

It seems like a decent posit that something major happened that affected Earth globally. Many massive construction projects (megaliths) in the ancient past just stopped. Further, new constructions of similar type never started up again. Again, it is conjecture that a cataclysm is the "why" but fascinating regardless. These guys and others such as Hancock raise many interesting questions about what we "know".

PS: one other tidbit -

The establishment record indicates that man on the North American continent got here with the Clovis people -

https://en.wikipedia.org/wiki/Clovis_culture

The dating puts that timeline within the range of the Younger Dryas. So if you dig anywhere across North America at a certain point you stop finding evidence of human habitation, the Clovis level. If you dig just below that you find a belt of nothing, just rocky debris. A university archeological team was digging in South Carolina (IIRC). They had gotten to the Clovis level and at the end of the dig the main archeologist decided to pointlessly keep going. He got well below the Clovis level and discovered human artifacts. So far the university has not funded another dig at that site. And my recollection is that peer reviews on what he found tore it apart. I believe this was in one of Graham Hancock's videos, I don't recall which one though. Was this evidence of an even earlier culture pre-dating the Clovis people? Could be as well as it could be a geographic anomaly shifted the levels but without further study you won't know.

...and don't even start on Lovelock cave and the Paiute Indians.....

/alternate history

edits: typos