Under most circumstances, milk that is long past its expiration date is a friend to no one. But this spoiled substance has found an unexpected niche in the field of archaeology as a surprisingly precise way to accurately date ancient pottery, new research suggests. The face-puckering technique is so exact that it can pinpoint the ages of millennia-old food containers to a couple of decades, or a “human life span,” reports Dalya Alberge for the Guardian.
Described last week in the journal Nature, the milk-based method may now be rejiggering the specifics of London’s prehistoric beginnings. Though the roots of the famous British city have typically been linked to its establishment as a town during the first century A.D., London’s pottery now hints that it may have been a place of significance as early as 3600 B.C., when it appears to have served as a gathering place for farmers.
The London artifacts—a large collection of mostly shards and fragments—have long been believed to be of particular significance, according to a University of Bristol statement. When researchers from the Museum of London Archaeology (MOLA) unearthed the objects while excavating a Roman cemetery at Principal Place, a development in London’s Shoreditch district, they suspected the artifacts’ origins were Neolithic, possibly from around the time when farmers first arrived in Britain.
But pottery from this chapter of human history is rare and difficult to date, in part because researchers have lacked a way to assess the age of these materials through radiocarbon dating—a type of chemical analysis that’s often used on organic materials, or compounds come from living organisms like bones.
Organic materials aren’t usually present in pottery itself. But if the final products are used to store animal products, they can leave traces behind. To determine the specifics of the Shoreditch collection’s creation, MOLA researchers found a way to extract and purify minute traces of animal fats found in the ancient pots, which once contained meat and dairy. The study marks the first time this method has been used successfully.
“Being able to directly date archaeological pots is one of the ‘Holy Grails’ of archaeology,” says study author Richard Evershed, a chemist at the University of Bristol, in the statement.
The analysis revealed that the Shoreditch pottery assemblage was likely in use 5,500 years ago, probably by early farmers who made cow, sheep or goat products—including milk, cheese, meat stew and yogurt-like beverages—a regular part of their diet, according to David Keys of the Independent.
This timeline seems in keeping with the arrival of farming populations in Britain around 4000 B.C. Evidence of Neolithic houses have been discovered elsewhere in the United Kingdom—and though similar findings have yet to be made in Shoreditch, study author Jon Cotton, a prehistorian at MOLA, tells the Guardian that the ancient site was probably well-suited for human and animal habitation. Boasting access to fresh water and ample greenery, he says, “[I]t was a good place to live.”