Ancient people may have moved some of the massive megaliths of Stonehenge into place by greasing giant sleds with pig lard, then sliding the giant stones on them across the landscape, a new study suggests.
After re-analyzing ceramic pots that earlier researchers believed were used to cook food, archaeologist Lisa-Marie Shillito concluded that many of those pots may have been used to collect fat that dripped off pigs as they were spit-roasted. The grease would have been stored as lard or tallow and used to lubricate the sleds most archaeologists believe were used to move the stones.
"Until now, there has been a general assumption that the traces of animal fat absorbed by these pieces of pottery were related to the cooking and consumption of food, and this steered initial interpretations in that direction," Shillito said in a statement. "But there may have been other things going on as well, and these residues could be tantalizing evidence of the greased sled theory." [Stonehenge: 7 Reasons the Mysterious Monument Was Built]
The pottery fragments came from Durrington Walls, a site near Stonehenge where workers lived while building the monument. Since excavations began in the 1960s, archaeologists have found a puzzling combination of artifacts at the site, including pottery fragments and animal remains.
Archaeologists can learn a lot about pottery fragments by analyzing their shape, size and the material they’re made from. For about 30 years, researchers have also used a technique called organic residue analysis to surmise what ancient people put in the pots.
By looking at traces of compounds left behind, including isotopes, or different versions of chemical elements, "we can determine what types of foods were processed in ancient pots," Julie Dunne, a biomolecular archaeologist at the University of Bristol in the UK, told Live Science. A 2018 analysis suggested that about a third of the pots archaeologists have found were used to cook pork. And they weren't just frying a bit of bacon, either.
"We find very high amounts of lipids in the pots," said Dunne, who was not involved in the current study. "The pots themselves are quite big, and they have high lipid signals, which means they were probably used to process a lot of animal products."
There's just one problem with the 2018 study's conclusion that the pots were used to cook pork: the pig bones found at the site came from carcasses that hadn’t been cooked in pots. The majority of pig bones found at the site are singed on the ends, suggesting they were spit-roasted over an open fire, and many of the skeletons were found intact, meaning they'd never been butchered, according to the study, which appeared online July 15 in the journal Antiquity. In any case, a whole pig couldn't have fit into a pot. That and other evidence led Shillito to argue that the pots weren’t for cooking food but for collecting and storing lard used in construction.
“The original paper is a perfectly valid paper,” Dunne said, noting that societies are complex and a single interpretation doesn’t always show the full story. After all, even with all the vessels available to people alive today, the same type of coffee cup might hold coffee, tea, water for painting and warm milk for a kitten.
In 2018, Barney Harris, a doctoral student of archaeology at University College London, led a simulation of the greased sled theory. He and his volunteers showed that 10 people can move a 1-ton (0.9 metric tons) stone at nearly 1 mph (1.6 km/h). Shillito's findings "correspond with unpublished observations made during my stone-moving experiment in London," Harris told Live Science in an email.
The greased sled theory is also supported by examples of workers from other civilizations independently developing similar methods. Depictions from Mesopotamia and ancient Egypt show workers apparently using liquid lubricant to move large stone blocks, and an experimental archeologist working on Easter Island used mashed papaya to assist in moving large stones.
"Tallow produced in the way described by the authors would also surely confer comparable benefits," Harris said.
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Originally published on Live Science.