WASHINGTON (AP) — Ancient stone tools found in western Ukraine may be the oldest known evidence of early human presence in Europe, according to research published Wednesday in the journal Nature.

The chipped stones, deliberately fashioned from volcanic rock, were excavated from a quarry in Korolevo in the 1970s. Archaeologists used new methods to date the layers of sedimentary rock surrounding the tools to more than 1 million years old.

“This is the earliest evidence of any type of human in Europe that is dated,” said Mads Faurschou Knudsen, a geophysicist at Aarhus University in Denmark and co-author of the new study.

He said it’s not certain which early human ancestors fashioned the tools, but it may have been Homo erectus, the first species to walk upright and master the use of fire.

“We don’t have fossil remains, so we can’t be sure,” said Roman Garba, an archaeologist at the Czech Academy of Sciences and co-author.