Dolmens: Discoveries and Riddles

Dolmens, the ancient stone tombs and/or ritual constructions, continue to interest me. Readers will remember I wrote The Dolmen, a very well reviewed horror tale whose lesson is, "If you're going to illegally import and entire dolmen, direct and all, you'd better sift through the dirt."
We keep finding new dolmens and new things about them. They were built over thousands of years, from England to Korea and south into the Middle East.    The basic dolmen, usually three vertical stone slabs with a capstone, had many variations, some much more elaborate.  Why are they found over such a range? Probably the same reason pyramids are: if you want to raise something that will last, pyramids and dolmens are two types that don't require much in the way of construction techniques.  (The best-known Egyptian pyramids show a very sophisticated system of design and construction, but there are cruder pyramids all over the world, many built of nothing but tramped-down earth.) Similarly, all you need to build a dolmen is four stone slabs and a HUGE amount of manpower.  
A dolmen reported last year from Galilee is decorated with rock art, a very unusual find: there is none like it anywhere in the Middle East.  The structure, with an interior chamber measuring about 6 square meters. is dated to approximately 4,000 years BP.  It is one of some 400 in a field near Kibbutz Shamir, but it's the largest, the most elaborate (surrounded by a boulder heap about 20m across and four smaller dolmens) and we have only fragments of knowledge about the people who built it. Israeli archaeologist Gonen Sharon notes the field of dolmens means, "a strong system of government was required here that could assemble a large amount of manpower, provide for the personnel and above all direct the implementation and control of a large and lengthy project.” Some stones weigh 50 tons.  
A cryptic message from the Bronze Age, only now being deciphered.  Is it any wonder I made one the center of a novel?