Geologists and archaeologists already knew that the bluestones used to build Stonehenge were transported from the Preseli Hills in western Wales. But, a new study has now identified the exact geological sources from which the stones were excavated about 3,000 B.C.
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The stones reportedly came from two bluestone quarries, Carn Goedog and Craig Rhos-y-felin some 180 miles from the monument in Salisbury plain. Normally, prehistoric builders traveled no more than 10 miles to collect stones for their structures.
The quarries, estimated at around 5,000 years old, are located on the northern side of the hills, surprising scientists who originally assumed the origin would be located on the south side that lies closer to the ocean.
A previous hypothesis theorized that the bluestones were floated along the coast by travelers. This theory was debunked in 2000 when an attempt to replicate this event failed. The discovery of the two quarries also negates speculation that the bluestones were pushed into the region during the Ice Age.
Theories that have resulted from the latest study suggest that the bluestones were transported on sleds by teams of "burly Stone Age Men," which geochemist at Aberystwyth University, Nicholas Pierce, says is highly plausible.
In terms of excavation, it is believed that the stones were cleanly removed with ropes and simple tools, like sandstone wedges. Due to clean extraction, Stonehenge buildings would not need to rework the bluestones in the same way as those who crafted Egypt's obelisks.
The other type of stone used to build the monument, a silcrete known as 'sarsen', are more locally sourced, but their exact origins remain unknown. These stones were used for the trilithons, the three-part structure built from one horizontal stone stacked on top of two others.
The specificity of the origins of the stones led archeologist at the University College London, Parker Pearson, to believe that Stonehenge might have represented a symbol of unity for British tribes facing threats to their economy and population. It is also believed that those who have been buried at the monument came from the same regions of Wales where the quarries were found.