Neanderthals and modern humans split from a common ancestor around 500,000 years ago, with Neanderthals leaving Africa for Europe and Asia long before modern humans joined them hundreds of thousands of years later. There, Neanderthals dispersed as far as Spain and Siberia. Our prehistoric cousins likely first reached Asia around 190,000 to 130,000 years ago, with another substantial migration to Central and Eastern Eurasia likely between 120,000 and 60,000 years ago. But how did they get there?

Since there isn’t enough archaeological evidence to reconstruct their migration paths, a team of anthropologists has turned to computer models. Their simulations mapped out possible routes Neanderthals could have followed to reach Asia, and suggest that by traveling during warmer periods and following river valleys, they could have traversed approximately 2,000 miles (3,250 kilometers) in less than 2,000 years.

“Our findings show that, despite obstacles like mountains and large rivers, Neanderthals could have crossed northern Eurasia surprisingly quickly,” Emily Coco, co-author of a study published yesterday in the journal PLOS One, said in a New York University statement. “These findings provide important insights into the paths of ancient migrations that cannot currently be studied from the archaeological record and reveal how computer simulations can help uncover new clues about ancient migrations that shaped human history.” Coco began the study as a doctoral student at New York University and is now a postdoctoral researcher at the University of Algarve.

She and her colleague’s models accounted for temperature, land elevation, ancient rivers, and glaciers. While scholars had previously used a similar approach to simulate human and animal movement, the anthropologists are the first to apply it to Neanderthals, according to the statement. In doing so, they found potential migration paths during two time periods characterized by a warmer climate: around 125,000 years ago and 60,000 years ago. The different paths, which made use of river valleys, would have taken Neanderthals to Eurasia’s Siberian Altai Mountains along roughly the same northern route through the Ural Mountains and southern Siberia within 2,000 years. Significantly, the paths align with known Neanderthal archaeological sites as well as areas occupied by Denisovans, with whom scientists know Neanderthals interbred.

“Neanderthals could have migrated thousands of kilometers from the Caucasus Mountains to Siberia in just 2,000 years by following river corridors,” Radu Iovita, the other co-author of the study and an associate professor at NYU’s Center for the Study of Human Origins, said in the statement. “Others have speculated on the possibility of this kind of fast, long-distance migration based on genetic data, but this has been difficult to substantiate due to limited archaeological evidence in the region. Based on detailed computer simulations, it appears this migration was a near-inevitable outcome of landscape conditions during past warm climatic periods.”

Coco and Iovita specify, however, that their model does not consider every possible element that could have influenced Neanderthal movement, such as resources, climate change, short-term weather patterns, vegetation preferences, and previous occupations, among others. Still, in the absence of archaeological records, computer simulations provide a viable method of tracing the footsteps of prehistoric people—even though it’s not nearly as creative as searching for pitstops in Viking migration routes by sailing a Nordic clinker boat along the frigid Norwegian coast.