New clues from Ukraine hearths in the Last Glacial Maximum (LGM)

Mastering the use of fire transformed life for ancient people, letting them prepare food, light up the darkness, and survive harsh cold, among many other benefits.

Evidence suggests this know-how goes back at least a million years. Fire repeatedly proved crucial across human history, yet its importance would have been even more pronounced in certain periods.

Fire in the Last Glacial Maximum (LGM)

One such period was the Last Glacial Maximum (LGM) - the coldest phase of the most recent glacial period within Earth’s current ice age - when gathering around a hearth would have seemed an obvious advantage.

Even so, although conditions were extraordinarily frigid, archaeologists have found surprisingly little sign of people using fire during the LGM, which ran from roughly 26,500 to 19,000 years ago.

A new study set out to tackle this puzzle by examining the remnants of three ancient fireplaces from an archaeological site in present-day Ukraine. All three are linked to human occupation at the site during the LGM.

These hearths add fresh detail to late Upper Palaeolithic pyrotechnology - a long stretch of icy millennia in which fireplaces appear, oddly, to be scarce in the archaeological record.

"We know that fire was widespread before and after this period, but there is little evidence from the height of the Ice Age," says co-author William Murphree, a geoarchaeologist at the University of Algarve in Portugal.

Earlier studies have indicated that Upper Palaeolithic communities relied heavily on fire, which underpinned essential tasks that would have been difficult or impossible without it.

"Fire was not just about keeping warm; it was also essential for cooking, making tools, and for social gatherings," says co-author Philip Nigst, an archaeologist at the University of Vienna in Austria.

The researchers note that the LGM brought "rapid climatic deterioration" to Europe, producing extremely cold and arid conditions that drove habitat loss and increased geographic isolation. In that setting, it seems counter-intuitive that people would deliberately make fewer fires.

One possibility is that severe cold reduced tree growth across steppes and grasslands, shrinking the supply of firewood. Another is that people continued to light fires as often as before, but the brutal conditions during and after the LGM erased much of the physical evidence.

There is also the chance that the apparent pattern is misleading - an artefact of modern publication bias rather than a genuine drop in fire use.

Because the picture remains uncertain, finding several LGM hearths could be particularly informative. Beyond illuminating ancient fire practices, such discoveries may help explain why fireplaces from this interval seem so rare.

The Korman' 9 hearths on the Dniester River, Ukraine

To investigate, the team studied three hearths previously unearthed at Korman' 9, a site on Ukraine’s Dniester River. They applied a suite of geoarchaeological methods to recover fine-grained information about fires made tens of thousands of years ago.

Drawing on microstratigraphic, micromorphological, and colourimetric analyses, they concluded the remains came from flat, open fireplaces, with wood serving as the primary fuel in most cases.

Although the structures were straightforward, the fires may have heated the ground to 600 degrees Celsius. That level of heating could imply the flames themselves were well above that temperature, pointing to notable pyrotechnic skill even amid dramatic climatic disruption.

Large charcoal pieces were scarce, which limited identification of the dominant fuel. Still, assessment of the charcoal that was available suggested spruce wood was most common.

Bone traces, repeated visits, and unanswered questions

The hearth deposits also held traces of bone, though the reason for this is not yet clear, says co-author Marjolein Bosch, a zooarchaeologist affiliated with the University of Vienna, the Austrian Academy of Sciences, and the Natural History Museum Vienna.

"Some of the animal bones found at the site were burnt in a fire with a temperature of over 650 degrees Celsius. We are currently investigating whether they were used as fuel or just accidentally burned," Bosch says.

Variation between the three hearths may indicate separate occupations at Korman' 9 - perhaps separated by weeks, or even centuries. Alternatively, the differences could reflect specialised hearths used within a single occupation for distinct tasks or at different seasons.

"People perfectly controlled the fire and knew how to use it in different ways, depending on the purpose of the fire," Nigst says. "But our results also show that these hunter-gatherers used the same place at different times of the year during their annual migrations."

Although at least some groups evidently maintained strong pyrotechnic capabilities during the LGM, further work is needed to understand why so few comparable hearths have been identified at sites of the same age.

"Was most of the evidence destroyed by the ice-age-typical, alternating freezing and thawing of the soil?" Murphree says.

"Or did people not find enough fuel during the Last Glacial Maximum?" Nigst adds. "Did they not use fire, but instead relied on other technological solutions?"

The study was published in Geoarchaeology.