The world’s oldest pieces of clay pottery, recovered from the banks of the Amur River during the 1970s and ‘80s, date to the tail end of the last ice age—a tough time to live in Siberia, where the 28 ceramic shards were found. Now, a new chemical analysis of these 12,000- to 16,000-year-old artifacts suggests the Russian Far East’s residents navigated the harsh climate with the help of ancient “hot pots,” defined by Atlas Obscura’s Matthew Taub as “heat-resistant ceramics that preserved precious nutrients and warmth.”

By analyzing the millennia-old leftover fats baked into the pottery, researchers at the University of York in England were able to identify differences between the diets of two ancient Russian cultures. The Gromatukha, who lived near the Middle Amur and the west bank of the Zeya River, mainly cooked land animals, while the Osipovka, who lived near the Lower Amur, preferred fish, reports the team in the journal Quaternary Science Reviews.

The new Osipovka findings build on a previous theory about how the ancient community lived, archaeologist Vitaly Medvedev, study co-author and a member of the group that originally found the of pottery, tells the Siberian Times.

“There is an abundance of fish in the Amur,” says Medvedev. “And all our finds pointed to [the people being] fishers. Academician Alexey Okladnikov even named the people of Lower Amur … ‘ichthyophages,’ as their life was based on fisheries.”

Prior expeditions in the area have unearthed stone sinkers, or weights, the Osipovka likely used for net fishing in the river during salmon spawning season. According to Medvedev, archaeological evidence shows the ancient community smoked and dried a portion of their catch, preserving the fish for the winter season, and cooked the rest.

When Medvedev and his team first stumbled onto the pottery, its consistency resembled that of Play-Doh. The researchers had to store the shards in paper for a few days to allow them to harden; even then, the ceramics remained fragile—“like cookies,” as the archaeologist tells the Siberian Times.

The region’s acidic soil breaks down organic material relatively quickly, so conducting detailed chemical analysis of the pottery proved challenging. The researchers extracted fat molecules from powdered samples of the ceramics to look for signs that meat from either aquatic or land animals had been cooked in them.

In particular, the team looked for molecules specific to animals with a rumen, or first stomach, that breaks down dense vegetation into cud. Cattle, deer, sheep, camels and giraffes, among others, are all ruminant mammals.

Chemical traces of ruminant mammals showed up on the Gromatukha pottery shards, but not on the Osipovka samples. Per the study, the analysis found that the Osipovka pottery actually has more in common with Japanese ceramics used to cook fish around the same time period.

The people who invented these ceramic “hot pots” never met each other—but necessity is the mother of invention, and at the end of the ice age, warm food would likely have been a welcome treat.

“We are starting to understand that very different pottery traditions were emerging around the same time but in different places, and that the pots were being used to process very different sets of resources,” says Peter Jordan, senior study author and an archaeologist at the University of Groningen, in a statement. “The insights are particularly interesting because they suggest that there was no single ‘origin point’ for the world’s oldest pottery.”