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," 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."
     The pottery fragments came from Durrington Walls, a site near Stonehenge where workers lived while building the monument. For about 30 years, researchers have used a technique called organic residue analysis to surmise what ancient people put in the pots.A 2018 analysis suggested that about a third of the pots archaeologists have found were used to cook pork. "We find very high amounts of lipids in the pots," said Julie Dunne, a biomolecular archaeologist at the University of Bristol in the UK, 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. 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.
     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 Shillito's findings "correspond with unpublished observations made during my stone-moving experiment in London," Harris said.
     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.

Edited from LiveScience (July 2019)