Ancient Siberia was so nice, eastern European Neanderthals trekked there twice—even though they probably had to cross some 2,000 miles of tough terrain to reach it, a new study suggests.

A team of researchers has uncovered stone blades in Siberia’s Altai Mountains that bear a remarkable resemblance to known Neanderthal tools from modern Crimea and the northern Caucasus, located just north of the Black Sea. The group’s findings, published this week in the Proceedings of the National Academy of Sciences, hint that our long-gone cousins crossed the Eurasian continent about 60,000 years ago—an encore act to a similar eastward journey made some 40,000 years prior.

“Neanderthals were intrepid explorers in their own right,” says study author Richard Roberts, a geochronologist at the University of Wollongong in Australia, to Bruce Bower of Science News.

The team can’t conclusively say how long the journey took, or if it happened in fits and starts. But using the tools as an archaeological throughline, the researchers argue that at least some Siberian Neanderthals—whose origins have long been elusive—trace their roots back west.

Previous research has shown that a similar eastward trek occurred more than 100,000 years ago, when a separate population of European Neanderthals entered southern Siberia and settled in Denisova Cave, where they left behind a smattering of tools.

The team’s new findings come out of Chagyrskaya Cave, some 60 miles west of Denisova Cave, where around 74 Neanderthal fossils and 90,000 artifacts have been unearthed since 2007. Compared to the contents of Denisova Cave, the 4,000 or so stone tools found in Chagyrskaya are about 40,000 years younger. They also come with quite a different look, resembling flaked Micoquian blades—archaeological fixtures of central and eastern Europe, where they were used to hunt and butcher bison and horses, according to a statement.

These differences suggest two separate groups of Neanderthals from Western Eurasia, each with their own distinctive toolmaking style, managed to reach eastern Asia, Jean-Jacques Hublin, a paleoanthropologist at the Max Planck Institute for Evolutionary Anthropology in Germany who wasn’t involved in the study, tells Science News.

DNA seem to back this argument up: As Dyani Lewis reports for Cosmos, a separate analysis conducted last year found that Chagyrskaya Cave Neanderthals are a closer genetic match to their kin from Europe than their cousins in Denisova Cave.

Though the motivations for the migration remain uncertain, Neanderthals were probably following migrating herds of prey, write the researchers in the study. As warm spells shrank the size of the Caspian Sea, they may have had an easier time forging a path, says study author Maciej Krajcarz, a geoarchaeologist at the Institute of Geological Sciences in the Polish Academy of Sciences, in the statement.

Searching for more tools along the midpoints of this journey may yield further clues to these early hominins’ travels, Roberts tells Cosmos. Further excavations could also tweak the story, points out Steven Kuhn, an archaeologist at the University of Arizona, to Science News. Rather than dispatching a single enduring group all the way to Siberia, different populations of Neanderthals may have simply passed along toolmaking techniques in an eastward relay.

Either way, findings like these will help researchers “start to piece together the intriguing story of the easternmost Neanderthals,” says study author Kseniya Kolobova, an archaeologist at the Russian Academy of Science's Institute of Archaeology and Ethnography, in the statement.