Opiates are nothing new—the opium poppy has been cultivated by humans for almost 5,500 years. But just how quickly and widely the use of poppy-derived narcotics spread across the world is under debate. A new analysis of a small jug held by the British Museum, however, reignites the debate whether poppy products were widely traded across the eastern Mediterranean during the Late Bronze Age.

The BBC reports that the research is based on a surprisingly controversial type of pottery, the Base Ring juglet. More than 50 years ago, then-research student Robert S. Merrillees first suggested that the little pottery vessels, which look like inverted poppy seed heads, were used to hold opium. With most of the jugs produced in Cyprus, an early hotbed of poppy cultivation, and found in many archaeological sites in the eastern Mediterranean, he hypothesized that the vessels were used in an organized opium trading network. The problem is, there was no physical or documentary evidence to support the idea.

While Merillees’ own analysis of one jug of unknown provenance in the late 1980s found traces of opium, his work was critiqued for its vague methodology, and his findings were not considered conclusive evidence.

In 2016, researchers from Tel Aviv University revisited Merillees’ idea, but their own analysis of juglets did not detect any residue of opium, just other oils and perfumes. A University of York research team led by Rachel K. Smith of the Centre of Excellence in Mass Spectrometry is the latest to take on the juglet question. This time around, the team looked at a juglet found in Cyprus held by the British Museum. Unlike other juglets, this one remained sealed, adding an extra layer of protection for the residue inside.

The team used high-performance liquid chromatography-electrospray ionisation tandem mass spectrometry to detect the alkaloid papaverine, unique to opium poppies. But even in the well-preserved sample in the juglet, the levels were low, raising questions whether traces of the poppy could survive on things like potsherds or in jugs that were not sealed. The research appears in the journal Analyst.

While the presence of the poppy alkaloids is interesting, it doesn’t mean that the juglets were part of a regional opium trading network. “We found the alkaloids in degraded plant oil, so the question as to how opium would have been used in this juglet still remains,” Smith says in a press release. “Could it have been one ingredient amongst others in an oil-based mixture, or could the juglet have been re-used for oil after the opium or something else entirely?”

Archaeologists have previously suggested the juglets were used to hold poppy seed oil, a non-narcotic substance that would also have poppy alkaloids. According to a press release from the British Museum, the oil residue suggests the juglets' contents weren’t consumed but rather were used for anointing or as perfume, which was very common in the ancient world.

“It is important to remember that this is just one vessel, so the result raises lots of questions about the contents of the juglet and its purpose,” says co-author Rebecca Stacey of the British Museum. “The presence of the alkaloids here is unequivocal and lends a new perspective to the debate about their significance.”

Andrew Lawler at Science explains that archaeologists have been very conservative when assessing whether ancient cultures took recreational or ritual drugs. But recent research has begun to reinterpret some ancient writings and images and new analysis techniques have found opium poppy residue and other compounds dating back thousands of years, suggesting we have a lot more to learn about humanity’s history with drugs. Or love affair with poppy seeds.