Extensive Ancient Underground Networks Discovered Throughout Europe

I have heard it postulated that, at one time in Earth's history, the atmosphere contained a "water blanket", consisting of an immense amount of water which shielded the earth from large amounts of radiation. This blanket would also have had the effect of distributing the Sun's heating effect evenly between the poles, resulting in a very mild climate over all the Earth. If this theory were true, it may have been possible that this "water blanket" was destroyed by some collision or near miss and could account for such a large change in the depth of the sea.

Susan, those are reasonable points. I appreciate your input.

I wonder though about the cost benefit as the absolute cost in terms of resources and requirements are no different then than they are today. It seems to me that carving living quarters out of hard rock is one of the most cost prohibitive construction methods available. And I think tunnels are VERY dangerous as a retreat from marauders and outlaws. All the attackers have to do is find the air vents and it's pretty much all over with.

I don't disagree with the predator animal idea, but the response to that threat seems to be the many thousands of dolmens scattered all over the world. They seem to me to be temporary 'safe rooms' particularly from large flyers and land based carnivores. I think there is a specific reason that almost all dolmens have very large and very heavy single slab stone roofs. Which , in my opinion is to keep something very large and very strong from entering the confined space. As you may know, there are two distinct styles of dolmen. On is a very heavy roof slab perched up on open stone pillars. They look to me way to much like a defense against very large flyers for it to have much other purpose.

The other style is a small room built with very large stone blocks, again with a very large flat stone roof. This type though has an entry hole close to the ground that is just large enough to allow women and children to crawl through. (On average, the entry holes are round and about 2 feet across.)

In my upcoming book, I will make the case that both giant humans and some mid sized dinosaurs co-existed with Cro Magnon and several other Hominid species up into the mid to late Holocene, including modern times. 14' to 16' giant hominids were able to defend against T-Rex and other mid sized to large carnivores. But modern human and smaller hominids were especially vulnerable. I have several copies of old tintype photos (if I had to guess I would say about 1850) of what appear to be Petrodactyl type flyers. Another later one is of a Triceratops. I can't prove they are authentic, but it was a long time ago, and a very difficult situation to 'fake'. All three are military photos, showing a group of military personnel (like a squad or column of men) with the animals.

Further, as the Earth was experiencing a rapid ice meltwater pulse at the time, (some experts think the ambient temperature was 27 degrees hotter than current) it seems to me that remediation of the heat index is a far better reason to go underground than security and safety from an external threat.

Anyway, thanks for your comment.