Though difficult to date, most agree they begin to appear between 12,000 to 7,000 years ago.
Dating when these rocks were made is a sketchy en-devour at best, and archaeological finds around them have been laid down in the subsequent millennia.
This design would certainly increase surface area on a plane of arched trajectory.
Covered in earth these structures are indistinguishable from their surroundings.
We continued shooting arrows out from behind stone defense lines for thousands of years all over the planet because quite simply, it was a good idea.
Megaliths have been found all over the world from the Orkney Islands in North Scotland , along the coasts of Ireland, England, the Iberian Peninsula which includes Spain and Portugal.
Some of these dolmen show evidence of having been backfilled and covered in plants. Some also show evidence of use as a burial grounds, but most do not.
Megalithic sites all over the world are staggering in their scale.The Great Wall of China has a double set of this defense strategy.The oval alignment of stones in the photo below it is found in South Sweden on the cliffs overlooking the Baltic Sea.A testament to how beautifully this design works is seen in a more recent fortress, Castiglione on Lago Trasimeno in Italy.The Chinese went to great lengths to secure their own borders and corridors.