Humans, Not Glaciers, Brought Rocks to Stonehenge — But Why and How Remain a Mystery
The megalithic formation of Stonehenge is one of the most enduring mysteries of the Neolithic era. The structure contains large stone slabs from Scotland, Wales and England, but no written explanation of who created the monument, why or how.
As for the latter, there has been some debate over exactly how these giant stones were transported from the farthest corners of the United Kingdom to their current home on Salisbury Plain, Wiltshire, England. More specifically, were they moved by people? Or glaciers?
Today, archaeologists write Earth and Environment Communications provide more evidence in favor of the human argument. By analyzing tiny grains deposited in rivers near the site, researchers can study how different materials traveled across the UK over extraordinarily long periods of time. It is not so much the contents of the Stonehenge samples as the absence of certain minerals that suggests human transport.
The absence of these minerals “makes the alternative explanation – that humans moved the stones – much more plausible,” lead author Anthony Clarke, of the School of Earth and Planetary Sciences at Curtin University, Australia, said in a statement.
“Stonehenge continues to surprise us,” added co-author Professor Chris Kirkland, from the School of Earth and Planetary Sciences at Curtin University, Australia. “By analyzing minerals smaller than a grain of sand, we were able to test theories that have persisted for more than a century.”
Learn more: Archaeologists suggest Stonehenge could have unified the people of ancient Britain
Where do the stones of Stonehenge come from?
The Stonehenge megaliths can be divided into three groups. Sarsens are larger stones forming the outer circle and inner horseshoe, and originally came from the West Woods, about 15 miles away. The bluestones weigh between 2.2 and 5.5 tonnes (2 and 5 tonnes) and come from Mynydd Presel, a mountain range in south-east Wales, around 230 kilometers from Stonehenge. The last is the Alter Stone, a 6.6-tonne (6.6 tonne) piece of Paleozoic red Ord sandstone from the Orcadian Basin of northeast Scotland, more than 435 miles (and 700 kilometers) away.
Clarke and Kirkland’s study focuses on blue stones. While most have suggested that these stones were moved by humans, using land and/or sea routes, there is another theory.
And how did the stones get there?
As rock erodes, it creates sediments – tiny grains and larger fragments that have been dislodged from the main body of the rock. These sediments contain mineral clues or “footprints” that can tell us where they came from and where they are found.
For this particular study, Clarke and Kirkland used apatite and zircon. The latter is, according to the American Museum of Natural History, the oldest mineral on the planet. (Examples found in Australia date back 4.2 to 4.3 billion years.) Zircons are exceptionally strong, chemically inert, and rarely disappear, making them particularly useful mineral “footprints” or geological time capsules.
In this case, what was interesting wasn’t exactly what they found, but rather what they didn’t find. If the bluestones had been transported by glaciers, researchers would expect to find substantial amounts of zircon that are 464 million years old, which matches the age of the bluestones themselves.
Instead, the ages of zircon found on Salisbury Plain were much older (1.7 to 1.1 million years), showing that it derived from an older rock. Meanwhile, the discovered apatite was much younger, around 60 million years old. Together these features match those of neighboring London Basin rocks and imply the recycling of local sediments rather than an influx of new sediments from Wales during the last ice age. Bottom line: “The ice almost certainly didn’t move the stones,” Clarke said.
The findings support previous studies, including a paper published in the Journal of Archaeological Sciences: Reports last year, which contradicts arguments that the “Newall Rock”, a blue stone, was transported by glacier. But how exactly humans moved these giant slabs of stone (and why) remains a mystery.
Learn more: The ancient burial site of the slabs may have inspired Stonehenge
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