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If the age estimate for the Spain find holds up, the new report adds to a “surprising number” of sites from deep in the Stone Age that retain evidence of small, intentionally lit fires, says archaeologist John Gowlett of the University of Liverpool in England.
Excavations conducted since 2011 at the Spanish cave, Cueva Negra del Estrecho del Río Quípar, have uncovered more than 165 stones and stone artifacts that had been heated, as well as several hundred animal-bone fragments displaying signs of heating and charring. Microscopic and chemical analyses indicate that these finds had been heated to between 400° and 600° Celsius, consistent with having been burned in a fire.
Walker’s group doubts that sparks from a brush fire near the cave’s entrance could have triggered fires five to seven meters inside the cave. Dry brush probably didn’t grow near the cave anyway, the researchers add. Geologic evidence suggests that around 800,000 years ago, the cave bordered a river and a swamp.
As at other sites with signs of ancient fire making, early Homo at Cueva Negra left behind a range of stone tools signaling advanced technical skills, Walker says. Those savvy toolmakers must have known how to select wood or stone suitable for striking sparks onto small piles of tinder, he proposes.
Dating of the ancient fire making depends on the researchers’ previous identification of a reversal of Earth’s magnetic field, known to have occurred around 780,000 years ago, in sediment just above where the burned material was unearthed.
Other researchers suspect Cueva Negra’s artifacts aren’t as old as reported. A team led by biological anthropologist Juan Manuel Jiménez-Arenas of the University of Granada in Spain says it’s hard to say where the finds originally lay relative to several reversals of Earth’s magnetic field preserved in the cave’s layers. A Homo species made tools there no more than about 600,000 years ago, the upper age limit in Europe for the types of stone artifacts found at Cueva Negra, Jiménez-Arenas’ group concluded in 2011 in the Journal of Archaeological Science.
Walker’s team says fossils of extinct animals excavated along with the stone tools support the older age for fire making in the cave. But even at 600,000 years old, the artifacts would still predate other evidence of controlled fire in Europe.
Editor’s note: This story was updated June 17, 2016, to correct the number of animal-bone fragments found with signs of heating or charring.